MPEC & BIENNIAL RADIOTHERAPY PHYSICS CONFERENCE 2014
31st August – 2nd September 2014 Scottish Exhibition & Conference Centre, Glasgow
ABSTRACTS
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CONTENTS
Sunday 31st August 2014 ...... 3 Didactic Workshop on Research Governance I ...... 3 Medical Device Safety – Managing Incidents ...... 4 Didactic Workshop on Research Governance II ...... 7 Monday 1st September 2014 ...... 9 Professional Session I ...... 9 Biennial Radiotherapy Physics Conference – Diagnostic Radiology in RT ...... 11 Trainee Session I ...... 15 Challenges in Medical Equipment Management ...... 20 Magnetic Resonance Scientific Session ...... 23 Biennial Radiotherapy Physics Conference – Brachytherapy ...... 27 Trainee Session II ...... 29 Innovation in Physiological Measurement Services ...... 32 General Imaging Scientific Session ...... 34 Woolmer lecture ...... 37 Professional Session II ...... 37 Magnetic Resonance Imaging in Radiotherapy ...... 38 Trainee Session III ...... 41 Innovation in Physiological Measurement Services ...... 46 Diagnostic Radiology Session I – Doses in CT ...... 50 Professional Session III ...... 54 Biennial Radiotherapy Physics Conference – Quality Control in Radiotherapy ...... 55 New applications in rehabilitation and movement analysis ...... 59 Diagnostic Radiology Session II – Fluoroscopy and General Topics ...... 64 Tuesday 2nd September 2014 ...... 68 IOP Plenary ...... 68 Update Scientific Session (Physical Agents, RPA) ...... 68 Biennial Radiotherapy Physics Conference – Dosimetry ...... 69 Update Scientific Session (MPE & RWA) ...... 72 Biennial Radiotherapy Physics Conference – Planning I ...... 73 Author Workshop ...... 77 Update Scientific Session – RWA2000 ...... 77 AAG Scientific Session – Big Data I ...... 78 Biennial Radiotherapy Physics Conference – Planning III ...... 82 AAG Scientific Session – Big Data II ...... 86 POSTERS ...... 90
Sunday 31st August 2014
Sunday 31st August 2014, 14.00 – 15.15 Didactic Workshop on Research Governance I
What is Research? Wyper D, Director of SINAPSE Email: [email protected] Website: www.sinapse.ac.uk In this presentation I shall outline the distinction between research and audit, and between service delivery research and biomedical research. I shall then discuss several issues that influence the quality of research: The benefits of having multi-disciplinary teams The need for multi-centre studies - and pitfalls in multi-centre studies How to attract adequate funding How to disseminate findings How to get research findings implemented.
Finally I shall discuss some of the challenges facing NHS employees doing research.
New Devices McCarthy J P, Clin Eng Consulting Ltd and Cardiff University School of Engineering email: [email protected] Developing a new device ‘in house’ for use in a research project is subject to different rules and regulations depending on the circumstances. REMEMBER a) Software can be a medical device in its own right even if running on a non-medical computer. b) Accessories (1) to a medical device e.g. a collimator to an LA, are treated as medical devices in their own right. 1. If the required device meets the definition of a ‘medical device’ (2) in the UK Medical Devices Regulations (2007) (based on the EU MDD, 1993 as amended), and if there is a commercially available CE marked device that meets the requirement, don’t reinvent the wheel. 2. If the purpose of the research project is to carry out a clinical investigation of a prototype medical device for which there is envisaged to be commercial potential, an application to MHRA for approval to continue must be made at least 60 days in advance. (3) MHRA will require the usual ethical and research governance assurances. 3. If the purpose of the device is to assist in carrying out the primary purpose of the research, and the device is not envisaged to fall into category 2 above, then the device probably does not fulfil the definition of a medical device and is not subject to the Regulations. 4. If the device does meet the ‘medical device’ definition, but is manufactured and used within the same corporate healthcare institution and there is no intent to commercialize the device, then MHRA guidance is that the Regulations do not apply since there is no ‘placing on the market’. (4) 5. If a CE marked medical device is to be used for a purpose not intended by the manufacturer - off- label use - then the risks and responsibilities fall on the research investigators and these must be made clear in the ethics application. (5) If commercial application is envisaged, then MHRA approval (point 2 above) will be required. 6. If a CE marked medical device is modified, either for routine clinical use or in the course of a research project, the institution authorizing the modification becomes the manufacturer. (5) 6(a) If the purpose of the research project is to investigate the clinical effectiveness of the modified device with a view to commercial application, then point 2 above applies. 6(b) If it is intended only to use the modified device within the same healthcare institution, then point 4 above applies. 7. Documented risk assessments, manufacturing devices using best practice, and meeting the MDD as far as possible, will meet professional obligations (CEng, CSci, HCPC). These steps will also reduce the chance of anything going wrong and give a strong defence in civil law if it does.
Difficult situations The situation where a medical device is being used in a collaborative research project between two or more corporate organizations throws up difficulties. If point 2 above applies, it is fairly straight forward because MHRA approval is sought and given for a multi-centre investigation. If point 4 applies and one institution makes a number of devices for use in other collaborating centres, have these devices been ‘placed on the market’? MHRA guidance (4) is helpful regarding research.
1. European Commission. MEDDEV 2.1/1 Definitions of "medical devices", "accessory" and "manufacturer". [Online] 1994. [Cited: 13 Aug 2014.] http://ec.europa.eu/health/medical- devices/documents/guidelines/index_en.htm. 2. MHRA. Legislation. [Online] Jan 2014. [Cited: 13 Aug 2014.] http://www.mhra.gov.uk/Howweregulate/Devices/Legislation/index.htm. 3. —. Clinical trials for medical devices. [Online] 18 June 2014. [Cited: 13 Aug 2014.] http://www.mhra.gov.uk/Howweregulate/Devices/Clinicaltrials/index.htm. 4. —. In-house manufacture. [Online] 2013. [Cited: 13 Aug 2014.] http://www.mhra.gov.uk/Howweregulate/Devices/Complyingwithlegislation/ActiveImplantableMedicalDevice sDirective/Inhousemanufacture/index.htm. 5. —. MDA/2010/001 Medical devices in general and non-medical products. [Online] 04 Jan 2010. [Cited: 13 Aug 2014.] http://www.mhra.gov.uk/Publications/Safetywarnings/MedicalDeviceAlerts/CON065771.
Sunday 31st August 2014, 15.45 – 17.15 Medical Device Safety – Managing Incidents
A model of interactions between medical devices, clinicians, patient and supporting infrastructure for investigating the causes of adverse events involving medical devices 1Amoore J N, 1Medical Physics, Crosshouse Hospital, NHS Ayrshire and Arran, Scotland. email: [email protected] Background. Recognition of the need to learn from adverse events to minimize Device Operator repetitions (1, 3) has highlighted the importance of identifying the causes. Too often the causes of medical-device related incidents Infrastructure are ascribed simply to Device or Operator or unknown. Some recent work involving surgical adverse events has sought to Patient characterise the nature of the causes (4). An approach to cause identification is developed from a model of interactions between medical devices, clinicians, patient and supporting infrastructure within the clinical environment (Figure 1). Methods. The approach is based on the interaction model, published classification methods (2) and review of incidents, their nature and causes. Three key groups (Device, Operator, Infrastructure – supporting systems and environment) with logical structured sub-groups provide the main focus of the approach, supplemented by groups addressing Tampering, Patient-Clinical (patient-device interactions), Unknown and No incident. Infrastructure includes procurement and commissioning, utilities, layout, mounting, lack of equipment and maintenance. Operator includes misuse (contrasting with poor ergonomic design, a device subgroup), device set up, failure to follow procedures, failure to be trained, distraction, concentration and criminal intent. Results. The approach was applied to case reports from the literature where it helped identify wider causes – average 2.6 causes per incident. The approach highlighted how operator, device and infrastructure failures combined to cause incidents. Analysis of an anonymous database of 1404 incidents in revealed how the nature of the causes differ between device types (Figure 2).
50% All devices 40% Infusion devices 30% Patient monitor 20% 10% 0% Device Operator Infrastructure Tampering Patient - Clinical Unknown
Discussion. Identifying the causes of adverse events is typically difficult with tools such as root cause analysis employed to assist investigations. The approach developed here is designed to follow natural processes of clinical practice and the interactions involved. It assisted identification of the causes in the retrospective analyses, but needs to be tested by different groups. Conclusion. The model was tested by application to published incident reports and to a database of anonymous medical-equipment related adverse events. Its application to published reports shows that it can clarify the underlying causes – typically several causes in any incident. References 1. Amoore JN, Ingram P. Learning from adverse incidents involving medical devices. BMJ 2002;325:272. 2. Anon, ECRI Institute's Medical Device Safety Reports (MDSR) database, www.mdsr.ecri.org. 3. Chief Medical Officer. An organisation with a memory: report of an expert group on learning from adverse events in the NHS. Department of Health. London. 2000. 4. Weerakkody RA etal. Surgical technology and operating-room safety failures: a systematic review of quantitative studies. BMJ Qual Saf 2013;22:710-718
Medical Device Development – Risk Management Patel M, Humphries M PA Consulting Group, Cambridge Technology Centre, Melbourn, UK email: [email protected] Risk Management is critical, and challenging to implement pragmatically during early phase development. Pragmatic, compliant Risk Management currently challenges many medical device manufacturers in the NHS and start-up companies. The harmonised risk management of medical devices standard, BS EN ISO 14971:2012, gives presumption to conformity to some aspects of the Medical Devices Directive (MDD) along with other harmonised standards. BS EN ISO 14971 is a process standard that establishes the requirements for risk management to determine the safety of a medical device. The challenge for developers is to determine how best to implement the standards during the ‘proof-of-concept’ phase as at this point of development it is not clear if the device is feasible in terms of technology and market need.
A further challenge is to consider how to maximise investments in prototypes when the appropriate risk management approach has not been followed from the start. From experience in the NHS and PA Consulting, I have come across many sophisticated prototype medical devices requiring CE marking. In the NHS, the use can be limited to patients of the same legal entity (‘exclusion’ in MDD). However challenges arise when the prototype device is further developed and is to be CE marked – either by the NHS Trust or a commercial company in the absence of Risk Management File as per BS EN ISO 14971. Whilst undesirable, if the safety and efficacy of the device can be assured then a carefully structured and planned retrospective risk management file may be accepted for BS EN ISO 14971 submission. Retrospective risk management includes following all processes described in the standard. As the components are mostly identified for application at this stage, risk control options analysis will be limited. The manufacturer needs to prepare a risk management plan so that the notified body is able to review the process followed. Although the first few phases of product development have already been completed, risk management activities need to be defined and a comprehensive risk gap analysis conducted before progressing to further stages.
Putting in place the right risk management processes and tools, is important for your development, and knowing how to use them correctly is critical. The gap analysis above may be based around FTA, FMEA or FMECA depending on the status of prototype development. The scoring in the analysis plays an important role in identifying risks within the system. Many manufacturers are uncertain as to how best to construct their risk matrix tables – what is an acceptable risk? Whether to use qualitative or quantitative scoring for probability scores? Whether to use ‘detectability’ or ‘P1 and P2’ scoring? Such decisions are important as they have significant impacts on safety and compliance with the standard. For example, consider probability and detectability, where the probability score P1 is a likelihood of failure occurring and P2 is likelihood of this failure resulting in harm. To clarify the differences, consider a motoring analogy - if a car braking system fails and the car is designed to detect the failure, then the ‘detectability’ score is high which would reduce the overall risk score significantly (but would not necessarily reduce the potential for harm). If the P2 score is used for the failure, the score will not reduce until the car system is designed to not only detect but also prevent harm. Even after deciding the scoring mechanism, the next challenge is how to score the severity of the failure. For example, a trip hazard – there is a range of possibilities with the hazard of a cable lying on the floor, from brain haemorrhage to minor shock. Where should we set the score in the analysis – is it correct to use the worst case or the most likely?
An assessment of the safety of optical light sources used in the head of the Elekta Agility linear accelerators Swift C, Allan D, Christie Hospitals NHS Trust, UK. email: [email protected] Linear accelerators (LINACs) are widely used within radiotherapy departments for delivering a targeted beam of high energy x-ray photons to treat disease. Tungsten multi-leaf collimators (MLCs) are now widely used to restrict and shape the aperture over which the radiation will be delivered. This enables the LINAC to deliver a tailored dose profile to the disease site more accurately, whilst conserving surrounding healthy tissue. The most precise treatment methods, such as Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT), require dynamic movement of these MLCs during treatment.
To this end sophisticated systems have been developed to accurately monitor the position of each collimator leaf within the field. The medical LINAC manufacturer Elekta previously utilised an optical imaging system which tracked the position of each MLC leaf by using reflectors positioned on the top side of each collimator and illumination by a halogen lamp. Unfortunately these reflectors degraded over time due to repeated high energy x-ray exposure, leading to machine down-time for periodic replacement. More recently, this has been superseded by a system based on the fluorescence of ruby tips placed on the upper side of the collimator leaves. These fluoresce under 410nm blue light from 3 high intensity LEDs with a maximum intensity at 410nm, and are imaged by an optical system similar to that used previously. This has resulted in a more reliable and robust leaf positioning system.
However the use of intense blue light sources presents a potential optical hazard. This is not a problem during normal use as the blue light is filtered out before it reaches the patient by means of a dichroic interference filter placed at the bottom of the LINAC head. There is however potential to view the intense blue sources with this filter removed during servicing and hence there is a potential hazard for LINAC service engineers. The true hazard posed to the unprotected eye was unknown so a full assessment of the optical hazards was undertaken. This involved the use of spectroradiometric measurements of the source and an evaluation of its hazards with respect to exposure limit values for UVA, the blue light hazard and the retinal thermal hazard. The most restrictive case was found to be the blue hazard limit, where the safe viewing time could be as short as 25 seconds. The exposure limit value for UVA was found to be less of an issue with the exposure limit values being reached in 49 minutes, whilst the retinal thermal hazard exposures were found to be within safe exposure limit values. It was found that the eyewear recommended by the manufacturer for engineers working on the LINAC head with the filter removed is more than sufficient to limit eye exposures to satisfactorily below the maximum permissible exposures set in UK regulation.
Under Pressure: The importance of matching consumables to medical syringe pumps and the role of the clinical engineer Lee P, ABM Health Board, Swansea, UK email: [email protected] Background The effective management (MHRA 2014) and safe use of medical infusion devices (MHRA 2013) often falls under the umbrella of the clinical engineer and matching these devices to generic consumables is raising new issues for the profession. Luer lock syringes sold in the UK must conform to the ISO standard (ISO 7886 part 2) for use in power driven syringe pumps and all steps are taken to ensure only syringes that conform to this standard are purchased for use.
Any increase in force to activate the initial movement of the syringe may cause a delay in therapy, any significant increases may cause the device to alarm that an occlusion has occurred (as the force required to overcome the initial stiction may be greater than the alarm setting) MHRA issued a number of alerts (MDA 2013/068, 2014/003) focussing on stiction and the risk if interruption of IV therapy
METHOD. A variety of consumables (50ml luer lock syringes, extension lines, IV cannula) and sterile water used for each of the tests. The Alaris GH syringe pump was used and set at two infusion rates to reflect current IV therapy infusions. (6ml ml per hour and 100 ml per hour). A software programme was written (in-house) to read (real-time) the force pressure off the pump’s strain gauge to indicate the force required to enable each syringe to start delivery and maintain the delivery of the medication at the set rate. Both the starting force and running force were measured.
RESULTS Varying forces and pressures can be seen when using newer style syringes and lines with valves. Test indicated force pressures in the region of 2 Kg (1 valve) to 2.75 Kg (2 valve) to infuse medications at rate of 6ml per hour. When syringes are used without the protection of anti-siphon valves then a significant lower operation pressure can be seen. The overall pressure to maintain therapy is lower.
DISCUSSION. The tests were only performed over a short period of time and did not account for the full travel of the syringe pump mechanism.Different manufacturers syringe pumps may be set at different force/pressure limits, or nor be able to be adjusted and this offers a set of risks that may not be able to be safely managed. Despite the lower force to administer medication without protected syringe lines (1 valve and 2); this doesn’t offer the full protection against accidental free-flow and this known phenomenon has led to serious harm.
CONCLUSION Protected syringe lines with in-line anti-siphon valves add a further restrictions to each infusion and this increased force needs to be overcome, by the pumping mechanism, before any medication can be delivered to the patient. The role of the clinical engineer is of significant importance in ensuring the purchase of the right consumables for Intravenous therapy and that they can be used safely on devices. The clinical engineer is able to carry out the necessary technical testing of products and can also advise on how best to adjust, or modify the existing infusion devices in use to ensure therapeutic efficacy.
REFERENCES ISO 7886 (pt 2) syringes for power driven syringe pumps MHRA alert BD syringe and stiction MDA/2014/003 | Issued: 17 January 2014 MHRA Alert BD syringe stiction; MDA/2013/068 | Issued: 21 August 2013 MHRA (2013) Infusion Systems, v2.1. December 2013 MHRA (2014) managing Medical Devices, Guidance for healthcare and social services organisations (April 2014)
Sunday 31st August 2014, 15.45 – 17.15 Didactic Workshop on Research Governance II
Submitting a Research and Development Application Walker A, National Coordinator, NHS Research Scotland Permissions Coordinating Centre, (NRS Permissions CC) Email: [email protected] This presentation will be presented by the National Coordinator of the NHS Research Scotland Permissions Coordinating Centre (NRS Permissions CC). This Centre is the Scottish national office responsible for providing a Scotland-wide feasibility assessment service to commercial and non-commercial researchers, as well as managing the streamlined process for obtaining NHS R&D permission for Scottish sites taking part in multicentre research studies. The talk will cover the necessary steps that UK researchers need to follow in order to apply for NHS R&D permission, which they will need before they can carry out research in the NHS in Scotland. The related cross-border processes with the rest of the UK nations will also be touched upon, since many studies are UK-wide. The processes/systems to apply for ethics favourable opinion and MHRA acceptance, will also be explained.
Introduction to Intellectual Property - A Physicists Perspective Brennan D, NHS Greater Glasgow & Clyde, Institute Of Neurological Sciences, Southern General Hospital, 1345 Govan Road, Glasgow, G51 4TF Email: [email protected] Over the last six years I have been involved in an exciting NHS and Glasgow University collaborative project. This project aims to take a novel MRI based metabolic imaging technology that we are developing, into the clinic, requiring a number of pre-clinical and clinical trials to be conducted. Thus, to take our GOLD technology beyond the bench requires significant amounts of investment, meaning that the current focus of our project is the commercialisation of the technology.
Initially my input into the project was purely scientific. However, having helped steer the project through the Scottish Enterprise Proof of Concept programme, and through a number of further translational steps with the aim of spinning out a company, I have come to understand the vital role that Intellectual Property (IP) plays in the commercialisation process.
This talk will draw from my recent experiences on the commercialisation path with our GOLD Technology. I will attempt to explain what IP actually is, why it should be important to you, and what steps you should take to protect it.
Monday 1st September 2014
Monday 1st September 2014, 09.00 – 10.30 Professional Session I
The new IPEM accreditation framework for Masters courses Parvin EM1, Harle J2, Lerski RA3 Evans JA4 1Department of Physical Sciences, The Open University, UK. 2Department of Medical Physics & Bioengineering, University College London 3 Department of Medical Physics, Ninewells Hospital and Medical School, Dundee 4Division of Medical Physics, University of Leeds Email: [email protected] In April 2014, IPEM launched its new accreditation process for Masters degrees in medical physics and biomedical engineering called the Masters Level Accreditation Framework (MLAF) : http://www.ipem.ac.uk/CareersTraining/MastersDegreeAccreditation.aspx
Designed to serve as a ‘kitemark’ of educational quality and suitability for university taught courses, it replaces the old scheme, in operation up to 2012, which accredited twenty university M-level programmes. While the old scheme awarded accreditation in terms of a programme’s suitability for the NHS training scheme for clinical scientists/engineers, this new framework offers a wider vision to be inclusive to the whole medical physics and biomedical engineering community. This includes courses targeting employment in academia and industry as well as the NHS/private hospital sector.
The new scheme also differs from the old in that it uses a learning outcome-derived approach. This talk will describe the framework and the required components for both physics and engineering streams and will outline the operation and governance of the new accreditation process.
Apprenticeships in Medical Engineering Young J, Lewis C A Medical Engineering & Physics, King’s College Hospital NHS Foundation Trust, UK. email: [email protected] Background: In 2005 a report commissioned by the South East London Workforce Development Commission identified a shortage of suitable candidates for Practitioner roles in some areas of Healthcare Science, and an aging workforce. In 2012, a report commissioned by NHS London (Scoping potential roles and associated training models for Assistant Healthcare Science Staff in a large Acute Trust), recognised that this situation still remained and indeed, the existing workforce was even closer to retirement. The Modernising Scientific Careers programme has, to date, sporadically addressed this problem, leading to gaps in the workforce and those exiting Practitioner Programmes not delivering staff that are fit for purpose. To address the shortage of Practitioners to maintain services it is essential to develop training routes for Assistants, Associates and Practitioners, to introduce young people into a career in Healthcare, specifically Healthcare Science, whilst ensuring routes for career progression, however it has been traditionally very difficult to get education providers to deliver the courses we would like in convenient locations for small numbers.
Methods. Following an investment from NHS London the Department of Medical Engineering & Physics at King’s College Hospital have developed a pilot apprentice scheme spanning several ‘equipment focussed’ areas within the Trust. The Assistant Clinical Technologist Apprentice Scheme (ACTAS) recruit 6 local young people and placed them onto the Trust’s existing Customer Service Apprenticeship Framework, allowing the Trust to draw Apprenticeship funding for this through an existing agreement with a local Further Education Provider. Once on the apprenticeship they were rotated through 4 ‘equipment focussed’ areas: Medical Engineering, Renal Technology, Theatres and A&E. In each area they were trained to a set of competencies developed according to the employers need. Competencies were signed off by Qualified Senior Practitioners. They also attend a weekly seminar program and modular Medical Device Training Courses, provided on-site by The Medical Room to gain the underpinning knowledge. The complete programme will culminate in the RegSciTech award. As registration requirements for Assistants and Associates are still unclear, the RegSciTech award should allow equivalence to any Approved Register that may arise.
Results. The pilot ACTAS programme has proven to be a real success. Several of the apprentices have been employed to substantive posts within the Trust when the programme is only 2/3rd complete. They have made significant contribution to the workload: In Medical Engineering, during 2 episodes where 100+ new devices entered the Trust due to expansions, repair turnaround figures were maintained, where in the past they would have fallen and there was no requirement for additional agency staff, as there has been in the past. In Theatres, down time has been minimised, as they are able to fault find and prepare devices prior to the qualified Medical Engineer arriving. Qualified practitioners in all areas have reported increased time for development of services. The programme was awarded the Health Education South London (HESL) Widening Participation Award 2013, the Advancing Healthcare Award 2014 ‘ Inspiring the Workforce of the Future’, and was shortlisted for a CSO award HESL has committed further funding to embed the current program and develop the next level on the career path. Local Councils are also keen to invest in the employment of local young people, given the high youth unemployment in the King’s locality.
This is an on-going project and there are still many things to be done to expand and improve on the scheme: Expand placement options, Critical Care, Maternity, Hospital@Night, iMobile, Respiratory Medicine Map to MSC Apprenticeship Frameworks when they are released, Engage with local schools and college to become feeder routes for suitable candidates, Develop career progression routes to Practitioner level, Hub & Spoke Training Model – working with other Trusts in London
Government reforms to the way Apprenticeships are delivered and funded should make apprenticeships more suited to Medical Engineering. There is a drive towards Employer led programmes with funding going directly to the employers rather than the education providers. The frameworks will be more ‘Outcome’ driven, rather than built around specific qualifications. This does, however, require engagement from the Healthcare Science community in the development of the frameworks.
Apprenticeship programmes can work for Medical Engineering, however, there is a need to work together on more generic programmes at the basic level to ensure viable numbers for training programmes and to allow for education to be local.
To Seven Day Working and Beyond: Highlights from the IPEM Radiotherapy Extended Hours Working Party Report’ Lawrence G, Blake S, Chalmers G, Lewis G, Patel I, Thomas S, Vinall A IPEM, York, UK. email: [email protected] Background. In February 2013 a multidisciplinary National Radiotherapy Implementation Group (NRIG) meeting was convened to discuss the possibility of extended hours working for radiotherapy departments. The Radiotherapy Patient Experience Survey in 2012 (1) had shown that a significant number of patients would be willing to attend for radiotherapy outside traditional core hours of Monday to Friday, 9.00am-5pm. Following the Prime Minister’s announcement in October 2012 of access to advanced radiotherapy for all patients, the Radiotherapy Innovation Fund provided a driver to increase the number of advanced treatments carried out in England. This has led to a significant increase in machine time required for patient specific QA (2). In addition, there is the need to ensure maximum efficiency of working for highly complex and expensive equipment as well as the annual increase in patients requiring radiotherapy (3). The February 2013 meeting indicated that there were a number of specific issues associated with the technical and scientific aspects of the service which would be seriously affected by extended clinical hours in a radiotherapy centre. With the demise of NRIG in April 2013 an IPEM Working Party was set up to consider these issues.
Methods. In October 2013 a meeting was held with the major radiotherapy manufacturers to assess the impact that extended hours working for radiotherapy departments would have for them. A survey of radiotherapy departments was then made to ascertain how much machine time is currently given to non- treatment related activity. Examples of extended hours implementation for small, medium and large sized departments were obtained. The Working Party considered three different models of operation namely a) extended hours Monday to Friday b) additional Saturday working c) seven day working. For each of these i) a treatment only service ii) a partial service and iii) a full radiotherapy service were considered. It was recognised that additional staff numbers would be required for the more comprehensive models but that the details would need to be determined locally.
Results. Issues such as availability of field service engineers, processes for ordering and obtaining spare parts, the effect on up-time guarantees, IT issues and the problem of a more thinly spread knowledge base were all raised by the manufacturers. The results of the QA survey highlighted the significant increase in time now allocated to non-treatment activity and the fact that a large number of departments have already implemented extended hours in some form. They have shown that the NRAG model of a service efficiency machine has been borne out in practice, as on average approximately 2500-3000 hours p.a. of non- treatment machine time are required in each centre.
Discussion. The report discusses different models of extended hours working, the issues to be considered and the staff groups involved. It makes recommendations based on the impact of the clinical service and the capacity required from the extended hours working period. These include staff numbers and skill mix together with arrangements for servicing and QA. It recommends a risk assessment based approach to consider the implications of each scenario.
Conclusion. A report has been produced detailing some of the issues associated with different models of extended hours working. It is hoped that this will assist service leaders in their negotiations with higher Trust management at a local level, by highlighting the problems and solutions for extended hours working in order to ensure a robust, safe and innovative radiotherapy service.
References. (1) Radiotherapy Patient Experience Survey 2013, NHS England, Nov 2013 (2) The Radiotherapy Innovation Fund: an evaluation of the Prime Minister’s £23 million fund, CRUK, July 2013 (3) Vision for Radiotherapy 2014-2024, CRUK/NHS England , March 2014
Monday 1st September 2014, 09.00 – 10.30 Biennial Radiotherapy Physics Conference – Diagnostic Radiology in RT
Cone beam CT optimisation for the Varian OBI system, and the impact on patient dose. Wood T J, Horsfield C, Moore C S, Beavis A W Radiation Physics Department, Hull and East Yorkshire Hospitals NHS Trust, Castle Hill Hospital, Cottingham, HU16 5JQ. email: [email protected] Background. Cone-beam CT (CBCT) is becoming increasingly common with the implementation of image- guided and adaptive radiotherapy. Whilst the benefits of CBCT are now well established, it must always be remembered that it is important to ensure imaging protocols are optimised to ensure that all doses of ionising radiation ‘are kept As Low As Reasonably Practicable (ALARP), consistent with the intended purpose’. However, this is not the case for the Varian OBI system as a single set of exposure factors are used for each anatomical site, independent of patient size. This may result in images that are not fit for clinical use on obese patients, whilst the radiation dose may be much higher than required for acceptable images on slim patients.
Methods. Image noise has been characterised using the Leeds Test Objects CT AEC phantom for a range of exposure factors. Regions of interest around the centre of this phantom have been used to measure CT numbers and image noise, which have been plotted as a function of phantom size. From these measurements, exposure factors for slim through to obese patients have been determined based on the principle of maintaining adequate image noise. Finally, the dosimetric consequences of these new exposure protocols have been investigated using PCXMC 2.0 to estimate organ doses for typical CBCT examinations on typical patients; this technique has been validated locally, and will be discussed briefly.
Results. Figure 1 shows image noise as a function of phantom size for a range of exposure factors, based around the default pelvic imaging protocol (125 kVp, 80 mA, 13 ms). These curves have been used to generate new exposure protocols for different sized patients (small, medium, large, extra large), with patient size determined by the initial planning CT scan. 60 55 50 45 40 35 30 40mA, 13ms 25 60mA, 13ms Standard Deviation (HU) 20 80mA, 13ms (Default) 15 80mA, 20ms 80mA, 26ms 10 0 10 20 30 40 50 60 Slice number Figure 1: Image noise vs phantom size (increases left to right) for a range of exposure factors.
Discussion. From the plots shown in Figure 1, it is clear that image noise increases rapidly with phantom size for the default exposure protocol. If adequate image quality is to be maintained for the largest patients, the exposure time needs to be doubled to ensure image noise is maintained at a similar level to the average patient (around slice 20-30), whilst tube current can be halved for the slimmest patients. Whilst the justification for using lower exposure factors on slim patients is relatively straightforward (e.g. we have achieved a factor of three reduction on 55-60 kg patients (typically 25-30 years old)), the IRMER practitioner justifying the exposures must be made aware of the potential doubling of dose for the largest patients; however, this must be weighed against the high likelihood of obtaining images that are of no clinical use on the default protocol.
Conclusion. Significant dose and image quality optimisation of the Varian OBI exposure protocols is possible through consideration of the image noise required for different size patients. This can potentially result in significant reductions in the dose burden of treatment verification imaging for slimmest patients, but may also indicate an increase is required for particularly obese patients.
Evaluation of the efficiency of computed tomography dose index (CTDI) used for cone beam CBCT scans using Monte Carlo technique. 1,2Abuhaimed A, 2Martin CJ, 1Sankaralingam M, 3Gentle D 1Radiotherapy Physics, Department of Clinical Physics and Bioengineering, Beatson West of Scotland Cancer Centre, Glasgow, UK. 2Department of Clinical Physics, University of Glasgow, Glasgow, UK. 3Health Physics, Department of Clinical Physics and Bioengineering, Gartnavel Royal Hospital, Glasgow, UK. email: [email protected] Background: Studies have shown that the computed tomography dose index (CTDI) within a phantom is an inappropriate dose metric for cone beam computed tomography (CBCT). A number of practical approaches have been proposed to overcome the limitations of CTDI100. The IEC have proposed the use of sequential measurements with a 100 mm chamber to cover the extent of the beam, and this has been recommended by the IAEA and IPEM for application in UK hospitals for beams of width >40 mm. The method involves the application of a correction factor to the standard CTDI100, which is equal to the ratio of two CTDI measurements free in air, for the beam width of interest and a reference beam width. The efficiency that is estimated as the ratio of CTDI to CTDI is considered to be a good indicator of the ability of the CTDI to record a value representative of the radiation exposure. The aim of this project was to evaluate the efficiency of this approach for different arrangements dosimetry using Monte Carlo simulation.
Methods: Monte Carlo (EGSnrc/BEAMnrc) and (EGSnrc/DOSXYZnrc) user codes were used to model the kV imaging system of Varian Truebeam linac. The Monte Carlo model was benchmarked against experimental measurements in standard PMMA head and body phantoms of diameters 16 and 32 cm. Three phantom lengths (150, 600, 900 mm) were used, where the later two lengths were considered to represent the infinitely long head and body phantoms, respectively. The efficiency was estimated as the ratio of CTDIIEC calculated based on the IEC approach to CTDI calculated within the infinitely long phantoms. Beam widths studied ranged from 20 mm to 300 mm. Four scanning protocols using two acquisition modes were simulated. Two reference beams of width 20 and 40 mm were compared. The efficiency values for the CTDIIEC,w were compared with those of the standard CTDIw.
Results: The efficiency values for the standard CTDIw for the scanning protocols used in this project were approximately stable over the beam widths (20 – 80) mm, where the efficiency was 79±1.2% and
74.2±0.9% of the CTDI,w for the head and body phantoms, respectively. When the beam width increased beyond 80 mm, the efficiency fell steadily, reaching ~30% at a beam width 300 mm for both phantoms as the beams extended beyond the edges of the phantoms. However, the efficiency values for the CTDIIEC,w were approximately constant over all the beam widths, where the values for the head and body phantoms were 82.2±0.9% and 75.7±0.7% of the CTDI,w, respectively. The difference between using 20 mm and 40 mm as the reference beam width was insignificant. The efficiency values for CTDIIEC,w calculated with 20 mm for the head phantom was within 0.39% of those calculated with 40 mm, and within 0.06% for the body phantom.
Discussion: The IEC approach has the advantage that the beam width plays no role in determining the efficiency. The efficiency values of the CTDIIEC,w for the head and body phantoms were approximately equal to the efficiency of the standard CTDIw used for the conventional CT scans with narrow beams reported by different investigators. Thus, the CTDIIEC successfully extends application of the CTDI approach to CBCT scans. However, as with the standard CTDI, the CTDIIEC,w efficiency is still underestimated the CTDI,w by ~18% to ~24%. The disadvantage of the approach for routine quality assurance is that the number of the scans that are required to assess the CTDIIEC,w for a scanning protocol using a 100 mm pencil ion chamber is relatively large.
Conclusion: The efficiency of the CTDIIEC,w approach was found to be similar to that of the CTDIw for standard CT scanners and it was not affected significantly by the width of the reference beam. Although the results have shown that the difference between using 20 or 40 mm as the reference beam was insignificant, we recommend using 40 mm rather than 20 mm as using a narrow beam width with the kV-system of TrueBeam might lead to uncertainty due to accuracy of the blade collimation.
Whole Body Effective Dose and Individual Organ Doses Due to Cone Beam CT (CBCT) and KV Planar Imaging on a Varian iX Linac 1Drake D, 1Medford B, 1M Oatey 1Kent Oncology Centre, MTW NHS Trust, UK. email: [email protected] Background X-ray imaging is being used more and more in radiotherapy to aid patient positioning (1). The Ionising Radiation (Medical Exposure) Regulations 2000 (2) requires that all medical exposures must be justified prior to the exposure being made; therefore a quantitative measure of the risk is required. This report presents estimates of the risk of fatal cancer induction (in the form of whole body effective doses) due to CBCT and KV imaging used during radiotherapy treatment. Additionally, mean and maximum point doses from CBCT imaging to organs considered at risk during radiotherapy treatment were measured and are presented.
Method Thermo-luminescent detector (TLD) chips (100H) were placed at approximately 40 different positions within a RANDO anthropomorphic phantom. The phantom was imaged using pelvis, thorax and head and neck CBCT clinical protocols on a Varian iX Linac. The TLD point dose measurements were used to estimate mean organ doses, allowing the whole body effective dose received by a patient to be calculated (using ICRP 103 weighting factors (3)). Similarly, entrance surface doses for KV planar imaging of the pelvis, abdomen and thorax were measured using an MDH 2026C pancake ion chamber. The software package XDose was used to calculate an estimate of the resulting whole body effective dose.
Results A subset of the results are presented in the table below. Whole Body Risk of Inducing a Peak Mean Dose to Effective Dose (mSv) Fatal Cancer (%) a Critical Organ (mGy) CBCT of Pelvis 3.8 0.021 9.6 (bladder and rectum)
CBCT of Thorax 3.0 0.017 8.2 (heart) / 6.5 (lungs) CBCT of Head and Neck 0.6 0.003 5.7 (salivary glands)
Pelvis 0.233 0.001 NA Lateral and AP KV planar Abdomen 0.306 0.002 NA Image of: Thorax 0.06 0.0003 NA
Discussion and Conclusion The total risk for a pelvis, a thorax and a head and neck patient over an entire radiotherapy course was calculated to allow radiotherapy staff to understand the implications of taking images. Given that the estimated risks of fatal cancer induction due to imaging are relatively low it is expected that the risk of detriment to treatment, due to more accurate patient positioning provided by imaging, outweighs the risk associated with dose from imaging. Additionally as the measured doses to individual organs were typically three orders of magnitude lower than organ tolerances used in radiotherapy (4), it was concluded that doses to organs at risk due to imaging are negligible when considering deterministic effects.
Key References 1. NHS National Cancer Action Team, National Radiotherapy Implementation Group Report, Image Guided Radiotherapy (IGRT), Guidance for Implementation and Use, August 2012. 2. The Ionising Radiation (Medical Exposure) Regulations 2000. 3. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP publication 103. Elsevier, Amsterdam: ICRP, 2007. 4. Quantitative Analysis of Normal Tissue Effects in the Clinic, Int. J. Radiation Oncology Biol. Phys., Vol76, No 3, Supplement, 2010.
4D CT protocol optimisation on the Philips Big Bore 16 slice CT scanner; practical experience and pitfalls. Wood T J, Horsfield C, Moore C S, Beavis A W Radiation Physics Department, Hull and East Yorkshire Hospitals NHS Trust, Castle Hill Hospital, Cottingham, HU16 5JQ. email: [email protected] Background. 4D CT is now becoming common place in many radiotherapy centres for assessing the motion of both the tumour and organs-at-risk, and hence ensuring the best possible treatment delivery for particularly mobile organs. In the Hull and East Yorkshire Hospitals NHS Trust, we have recently commissioned our Philips Big Bore CT scanners for the acquisition of 4D data sets via retrospective gating with the Varian RPM system. Initial measurements have demonstrated that protocol optimisation is essential for these types of examination due to the relatively high dose (compared with a standard fast-3D helical scan), and the additional complexity of the ‘phased’ reconstructions and the resulting image quality (including artefact induction).
Methods. The Leeds Test Objects (LTO) QUATTRO phantom has been used to characterise image noise properties and artefacts for a range of breathing rates and exposure factors on a ‘standard size’ chest phantom. Regions of interest were used to measure CT numbers and image noise in the soft-tissue and lung areas of the phantom. Further to this, the LTO CT AEC phantom will be used to investigate the impact of patient size on image noise and artefacts.
Results. The results of a region of interest analysis on the LTO QUATTRO phantom are shown in Figure 1. Figure 1(a) shows image noise for the manufacturers default 4D CT protocol (400 mAs per slice) compared with the standard 3D scan (under CT AEC control). Figure 1(b) shows the same comparison but with half the mAs per slice for the 4D CT images. No clinically significant artefacts were observed in the low dose images, but any increase in patient size does result in clear ring artefacts. 20 20
15 15 3D 20 bpm AEC (75 mAs) 3D 20 bpm AEC (75 mAs) 3D 20 bpm 200 mAs 3D 20 bpm 200 mAs 4D 10 bpm 200 mAs AvIP 10 4D 10 bpm AvIP 10 4D 10 bpm Phases 4D 10 bpm 200 mAs Phases 4D 20 bpm AvIP 4D 20 bpm 200 mAs AvIP 4D 20 bpm Phases 5
5 Standarddeviation (HU) 4D 20 bpm 200 mAs Phases Standard deviation (HU) deviation Standard
0 0 0 10 20 30 0 10 20 30 Slice number Slice number (a) (b) Figure 1: (a) Image noise for 10 and 20 bpm using the default 4D CT protocol (400 mAs per slice), and the current 3D protocol. (b) Image noise for 10 and 20 bpm using just 200 mAs per slice.
Discussion. The initial results of this study indicate that significant dose and image quality optimisation of the 4DCT imaging protocol is possible. With the manufacturers default protocol, image noise on a standard size patient is significantly lower than what is considered acceptable for the routine 3D scans (i.e. the dose is probably too high). By simply reducing the mAs per slice by a factor of two, the image noise properties on a ‘standard size’ patient can be matched to the current 3D fast helical scan. However, this significant reduction in tube current can lead to clinically significant ring artefacts in the final dataset if patient size is not appropriately compensated for. For this reason, the implementation of the Philips DoseRight ACS system is to be investigated.
Conclusion. It is proposed that implementation of appropriate exposure factor reduction, in conjunction with the CT AEC system, will result in significant patient dose reduction on standard size patients, whilst maintaining adequate image quality that is free from significant ring artefacts for all patients, independent of their size or breathing rate.
Monday 1st September 2014, 09.00 – 10.30 Trainee Session I
Minimising Occupational Eye Doses Within Interventional Radiology 1Magee JS, Martin CJ, Sandblom V 1Department of Health Physics, West House, Gartnavel Royal Hospital, Glasgow, UK email: [email protected] Background. The ICRP have proposed that the occupational dose limit for the lens of the eye is to be reduced from 150 mSv to 20 mSv1. Medical staff working in interventional radiology and cardiology have relatively high exposures compared to other occupational groups involved with X-rays2-5. Radiation doses to the eye have the potential to exceed the dose limit for interventional clinicians with high workloads, unless appropriate radiation protection measures are put in place6,7 Lead glasses can provide an important component of the protection and so a methodology needs to be developed to enable personal collar dosimeter results to be adjusted to take the protection provided into account. The aim of the study was to recommend a reasonable and conservative dose reduction factor (DRF) for lead glasses that can be applied to dosimeter results.
Methods. Lead glasses of varying design have been tested using an anthropomorphic phantom to simulate a patient and clinician in order to determine DRFs. Dosimetry records kept by Greater Glasgow Health Board for interventional radiology staff which included details of the number and types of procedure and the doses for each operator were reviewed to assess the potential importance of protective eyewear in limiting dose to be considered.
Results. The DRFs ranged from 1.4 to 7.6 depending on the design of the glasses, with the mean DRF being 4.5. When applying the mean DRF to a typical interventional employee’s workload then >900 procedures would need to be performed in one year before the limit would be exceeded, compared to 210 procedures if no glasses were worn.
Discussion. The glasses varied in design properties resulting in a range of DRFs. Glasses with large front lenses and side shields or angled lenses produced high DRFs compared to those which had thin metal frames and small lenses. DRFs were also found to be dependent on the experimental arrangement. For the least favourable orientation for poorly designed lead glasses the DRF was <2.0, and for most situations the DRF was between 3 and 6. Division by a DRF of 2 would appear to be a reasonable approach to account for the protection offered by lead glasses. Application of a DRF of 2 for those who consistently wear protective eyewear, coupled with training in use of other protective devices, should ensure that few exceed an annual dose of 15 mSv, for a typical workload.
Conclusion. Measurements of DRFs performed with lead glasses have shown that the dose to the eyes can be reduced by a factor of 1.4 – 7.6. The consistent wearing of glasses could eliminate the need for restrictions on workload for the majority of interventional clinicians. When assessing the dose to the eyes, it is necessary to take the protection provided by the lead glasses into account. If local measurements to determine the DRF for specific lead glasses are not possible, hospitals could apply a DRF of 2 for clinicians who consistently wear lead glasses of approved design.
Key references. 1. ICRP 2011 Statement on tissue reactions. ICRP 4825-3093-1464, April 2011. 2. Kim K P et al, 2008, Occupational radiation doses to operators performing cardiac catheterization procedures, Health Phys. 94, 211–27 3. Martin C J, 2009, A review of radiology staff doses and dose monitoring requirements Radiat. Prot. Dosim. 136, 140–57 4. Koukorava C et al, 2011 Doses to operators during interventional radiology procedures: focus on eye lens and extremity dosimeters. Rad. Prot. Dosim. 144, 482-486. 5. Vanhavere F et al 2012 ORAMED: optimisation of radiation protection for medical staff 7th EURADOS Report 2012-02 ISSN 2226-8057, ISBN 978-3-943701-01-2 6. Martin C J 2011b. What are the implications of the proposed revision of the eye dose limit for interventional operators? Br J Radiol, 84, 961-2. 7. Martin C J and Magee J S 2013 Assessment of eye and body dose for interventional radiologists, cardiologists, and other interventional staff. J. Radiol. Prot 33, 445-460.
The design and creation of a 3D printed mouse phantom from micro CT images for small animal PET/CT dosimetry purposes Hilton K, Hull and East Yorkshire NHS Trust, Cottingham, UK Email: [email protected] Background – It is thought that the high doses received by rodents during CT imaging may affect the results of longitudinal studies by causing significant DNA damage [1]. A literature search has shown that organ dose has been estimated using OSLD [2] and TLD [3-5] placed in mouse cadavers, and film in a simple Perspex phantom [1]. It is hoped that if a suitable phantom was designed, the doses measured in mouse cadavers could be replicated and further studies carried out without the need to sacrifice mice.
The aim of this study was to investigate the potential of using a phantom produced from a 3D printer for small animal PET/CT dosimetry. The phantom was designed so that film, TLDs and tissue samples could be inserted. A CT number to electron density calibration was undertaken in order to determine the appropriate materials to be used for the phantom and then also to determine the anatomical accuracy of the resulting phantom.
Methods – The CT number to electron density calibration of a Philips Bioscan BioPET/CT scanner (BIOSCAN Molecular Imaging Solutions, Washington DC, USA) was undertaken using the inserts out of a Gammex RMI 465 electron density CT phantom (Gammex Inc., Wisconsin, USA). The mean pixel value of a region of interest of each insert was measured in ImageJ v1.47.
Stereolithography (STL) files were created from micro CT images of a mouse cadaver. The files were created in DeVIDE v12.2.7 (Delft University of Technology, The Netherlands) and edited in MeshLab v1.3.2 (Visual Computing Lab, ISTI, CNR, Italy) and netfabb basic v5.1 (netfabb, Parsberg, Germany). The phantom was printed on an Objet 350 (Stratasys, Eden Prairie, MN, USA) 3D printer and then scanned so that it could be compared with the actual mouse.
Results – A phantom was produced which consisted of a 3D printed skeleton and a gelatine body. The mould for the gelatine was cast from a 3D printed model.
Discussion – Artefacts due to beam hardening and photon starvation resulted in CT numbers not on the calibration curve being measured in the mouse. This meant that an accurate estimation of the density of the skeleton was not possible. Due to the limited materials available for printing the electron density of the phantom skeleton was lower than that of cortical bone. However, even with this considered the resulting phantom more accurately represented a mouse than a simple Perspex phantom does. Further work can be carried out to modify the prototype phantom so that PET dosimetry can also be undertaken.
Conclusion – The aim of this study was to determine whether using 3D printed phantoms in small animal CT and PET/CT dosimetry was feasible. Although some improvements are required 3D printing definitely has potential in dosimetry.
Key references [1] Kersemans et al. Micro-CT for Anatomic Referencing in PET and SPECT: Radiation Dose, Biological Damage, and Image Quality, J. Nucl. Med., 2011; 52: 1827-1833 [2] Vrigneaud et al. Application of the optically stimulated luminescence (OSL) technique for mouse dosimetry in micro-CT imaging, Med. Phys. 2013; 40 (12): 122102-1 [3] Figueroa et al. TLD assessment of mouse dosimetry during microCT imaging, Med. Phys. 2008; 35 (9): 3866-3874 [4] Carlson et al., Small animal absorbed radiation dose from serial micro- computed tomography imaging, Mol Imaging Biol. 2007; 9: 78-82 [5] Rodt et al., Phantom and cadaver measurements of dose and dose distribution in micro-CT of the chest in mice, Acta Radiologica, 2011; 52: 75-80
Quantifying Underdosage Resulting from Incomplete Scatter Environments in Skin Brachytherapy 1,2Walker EP, 1Jones E, 1Aldridge SE. 1Medical Physics, Guy’s and St. Thomas’ Hospital, London, UK. 2School of Medicine, King’s College London, UK. email: [email protected] Background High dose rate brachytherapy has been identified as a treatment modality for skin cancers for some indications [1, 2, 3, 7]. Conventional treatment planning systems for brachytherapy utilise the TG-43 algorithm [4] for dose calculation. TG-43 calculates dose using single source dose superposition in an infinite water medium [5]. For most brachytherapy applications (e.g. pelvic targets such as gynaecological and prostate malignancies) this algorithm is acceptable as the targets are typically located deep within tissue and therefore within a relatively full scatter environment. However, for surface targets the formalism of a full scatter environment no longer holds [6]. Dose distributions calculated in the treatment planning system for such sites will thus be inaccurate, and may result in a superficial underdosage to the target. The aim of this project is to quantify the discrepancy between the treatment planning system and the actual treatment delivery due to incomplete scatter environments.
Materials & Methods Treatment planning will be performed using a CT dataset of the Freiburg flap on the Oncentra Brachy version 4.3 (Nucletron Elekta) treatment planning system (TPS) using an Ir-192 radiation source. Treatment delivery will then be carried out using the Flexitron remote afterloading device with the Freiburg flap and OncoSmart catheter system set up on a PTW 2-D array. The underdosage due to the incomplete scatter environment will be examined and compared with the dose distribution as calculated by the TPS. This will be performed for a range of irradiated areas with the source positioned at the surface of the array and at different source heights.
Results Results of this study are pending.
Discussion We envisage that the results obtained will enable more accurate treatment delivery of skin brachytherapy in the clinical environment.
Key references 1. Guix, B et al. (2000)Treatment of Skin Carcinomas of the face by High Dose-Rate Brachytherapy and Custom-Made Surface Moulds. Int. J. Radiation Oncology Biol. Phys., Vol. 47:95–102, 2. Köhler-Brock A, Prager W, Pohlmann S, Kunzw S. (1999) The indications for and results of HDR after loading therapy in diseases of the skin and mucosa with standardized surface applicators (the Leipzig applicator). Strahlenther Onkol 175 (4): 170–4. 3. Lovett RD, Perez CA, Shapiro SJ, et al. (1990) External irradiation of epithelial skin cancer. Int J Radiat Oncol Biol Phys 19:235–242. 4. Rivard MJ, et al. (2004) Update of AAPM Task Group No. 43 Report: A revised AAPM protocol for brachytherapy dose calculations. Medical Physics, 31:633–674. 5. Rivard MJ, Venselaar JL, Beaulieu L (2009) The evolution of brachytherapy treatment planning. Med Phys. 36(6):2136-53. 6. Raina S, Avadhani JS, Oh M, Malhotra HK, Jaggernauth W, Kuettel MR, Podgorsak MB. (2005) Quantifying IOHDR brachytherapy underdosage resulting from an incomplete scatter environment. Int J Radiat Oncol Biol Phys. 61(5):1582-6. 7. Sabbas AM, Kulidzhanov FG, Presser J, Hayes MK, Nori D. (2004) HDR brachytherapy with surface applicators: technical considerations and dosimetry. Technol Cancer Res Treat. 3(3):259-67.
Isotoxic Dose Escalation in Lung Cancer Radiotherapy: A Comparison of Techniques including Conformal, VMAT And Hybridarc 1Biggar R, 1Kirk J, 1Gilmore M, 1Mayles H 1Medical Physics Department, The Clatterbridge Cancer Centre, UK. email: [email protected] Background. Lung cancer represents 13% of all cancer cases in the UK, but accounts for a disproportionately high 22% of cancer deaths [1]. Local tumour recurrence is a common mode of radiotherapy failure in non-resectable locally advanced NSCLC cases. Some 90% experience local failure when treated using standard radiotherapy regimes of 52.5 Gy-55 Gy in 20+ fractions [2] and hence prognosis is poor. It has been suggested that dose escalation of NSCLC radiotherapy prescriptions improves local control [2]. The aim of this work was to investigate which radiotherapy planning techniques offer most superior plan quality/reduced OAR doses, such that the scope for isotoxic dose escalation is maximised. This was principally assessed by means of a final (escalated) prescription dose (FPD). FPD is an overall indicator of plan quality, as all OAR constraints, and coverage criteria are considered in the metric. Using FPD results and appropriate selection of planning technique may have the potential to improve patient outcomes.
Methods. A planning study was conducted using four historical stage II-IIIb NSCLC patients. Four planning techniques were inter-compared on these data sets, including: conformal radiotherapy (CRT), RapidArc (RA) (Varian, US), Hybrid-RapidArc (HRA) and HybridArc (HA). HRA is an Eclipse’ user developed ‘hybrid’ technique incorporating both CRT fields and RapidArcs [3]. HA is a commercial (BrainLab, DE) hybrid technique, combining fixed field IMRT with enhanced dynamic conformal arcs [4]. Class solutions were developed for use in the study. FPDs were calculated for all plans using the I-START trial [5] escalation framework, and exported plan DVHs.
Results. Despite inter-patient variations, HRA plans achieved the highest FPD compared to all other techniques. Alternatively, for a fixed dose protocol, (e.g. 55 Gy in 20) HRA results in a smaller aggregate of OAR doses- which is an equivalent statement. The cohort average FPD was 65 Gy, compared to the closest competitor of 63 Gy found with RA. Whilst conformity index was negligibly reduced. CRT and HA achieved far poorer FPDs of 58 Gy and 61 Gy respectively.
Secondary metrics of conformity index and delivery efficiency indicate relative inferiority of HA as a technique. HA plans required an average 23.5 MU/Gy, far greater than the 13.5 MU/Gy produced by RA plans. HRA and CRT were even more efficient at 12.1 MU/Gy and 8.1 MU/Gy respectively. However, large normal tissue doses are incurred as a result of CRTs geometric simplicity, reflected in a poor conformity index of 0.5 compared with HRA (0.76).
Discussion. These data suggest that CRT offers the least scope for isotoxic dose escalation, largely due to poor conformity/high OAR doses. It is acknowledged that CRT is still sometimes required, due to machine limitations or in circumstances of high spinal cord dose. HRA achieves a balance of conformity and a reduced low dose bath compared to standard RA. It is the technique of choice for achieving the highest FPD. Due to the limited size of the cohort, the statistical power is insufficient for this to be a significant difference. The FPDs are however indicative that the hybrid technique is at least equivalent to RA, if not slightly superior. HA does not allow much escalation, and target conformity is poor, probably due to lack of dose rate and gantry speed modulation in its conformal arcs. Furthermore, HA MU efficiency is unequivocally worse compared to all other techniques. Clinical implications include higher MLC transmission and leakage dose, longer beam on time, resulting in patient discomfort, potential for movement and a reduced clinical throughout.
Conclusion. HRA plans provide greatest scope for isotoxic dose escalation in this study, achieving 2 Gy higher prescriptions than RA. If dose escalation continues to show positive outcomes for NSCLC patients, HRA should be considered as a viable alternative to current planning techniques.
[1] CRUK. http://www.cancerresearchuk.org/cancer-info/cancerstats/types/lung/ [22 April 2014]. [2] Kong, F, et al. 2, 2005, Int J Radiat Oncol Biol Phys. Vol. 63, pp. 324-333. [4] Robar, J, et al. 4, 2013, Medical Dosimetry. Vol. 37, pp. 358-368. [5] UKCRN. http://public.ukcrn.org.uk/search/StudyDetail.aspx?StudyID=9703 [22 April 2014]. [3] Verbakel, W, et al. 2, 2012, Int J Radiat Oncol Biol Phys. Vol. 83, pp. 297-303.
Reducing toxicity in NSCLC radiotherapy using functionally-optimised VMAT 1Willett A, 1Uzan J, 1Rowntree T, 1Baker C 1Clatterbridge Cancer Centre Email: [email protected] Background. Lung cancer is the most common cause of cancer related death worldwide, with approximately 30% of people diagnosed in the UK surviving for one year after diagnosis [1]. The risk of potentially serious side effects from radiotherapy is managed by limiting doses that can be delivered to OARs (Lung, oesophagus, spinal cord and heart in this case). Often the dose that can be delivered to the tumour is limited by a need to keep the dose to the surrounding normal lung down to acceptable levels. This can lead to the patient not being able to undergo treatment, or not being able to receive a curative dose, resulting in reduced likelihood of tumour control. One theory is instead of assuming uniform lung function and minimizing damage to the lung as a whole; that preferentially preventing damage to highly functional regions will provide greater benefit. As it is theorised the dose to these functional regions is a better determinant of any potential complication [4]. Several techniques have been examined for their potential to reduce dose to the functional areas of lung [3,5]. The aim of this study was to look at potential reductions to mean dose to functional lung regions (fMLD) and associated toxicity risk (fNTCP) gained through volumetric modulated arc therapy (VMAT) optimization by avoiding areas of highly perfused lung as defined on a SPECT-CT perfusion image.
Methods. Five patients with NSCLC who were referred for radical radiotherapy and a prior SPECT-CT perfusion scan, based on poor global lung function were used in this study. Lung deemed functional was based on a threshold value (50% of maximum SPECT uptake) [2]. Plans were made without using any functional information to represent the ‘best’ clinical plan and again utilizing functional SPECT information. All of the plans met local departmental tolerances. fMLD was compared before and after functional optimisation. NTCP (for grade 2 and higher radiation pneumonitis) was calculated for each of the non- functionally optimized plans using the Lyman-Kutcher-Burman model. The TD50 parameter (dose at which 50% of the population experiences a complication) was adjusted to obtain a best fit NTCP model for the functional regions which resulted in the same population average NTCP as for the total lung DVHs. This ‘fNTCP’ model was then applied to the functionally optimized VMAT plans.
Results. All the functionally optimized plans showed a reduction in fMLD, whilst keeping other treatment parameters at a similar level. The reduction in fMLD ranged from 12-39% (median reduction 32%, p=0.0007). It was found that a value of 21.84 Gy for TD50 reproduced the population NTCP for conventionally-optimised plans. All the functional plans showed potential for dose escalation. Conventional VMAT Functionally optimized VMAT Patient NTCP (%) fNTCP (%) fMLD (Gy) NTCP (%) fNTCP (%) fMLD (Gy) 1 3 2.1 2.81 3.2 1.8 1.84 2 3.6 4.6 5.94 3.7 4.0 5.24 3 3.6 7.6 9.25 3.8 5.3 7.22 4 3.8 1.8 1.95 3.8 1.6 1.34 5 5 3.2 4.48 5.2 2.3 2.83 Table 1 – Improvement to fNTCP and fMLD with functional optimization.(Full-arc VMAT plans only)
Discussion/Conclusion. For this small cohort of patients, functionally optimizing based on SPECT-CT data led to a significant reduction in fMLD whilst retaining target coverage and other clinical tolerances. A custom NTCP model was used to quantify these reductions and found there was potential for dose escalating the functionally optimized plans. The benefits of preferentially avoiding functional regions of lung still need to be established in clinical trials; however this study highlights the potential reductions and viability of VMAT as an avoidance technique.
Key references. 1. Cancer research UK - http://www.cancerresearchuk.org/cancer-help/type/lung- cancer/treatment/statistics-and-outlook-for-lung-cancer 2. Christian, J, et al. 3, 2007, Radiotherapy and Oncology, Vol. 77, pp. 271-277. 3. Seppenwoolde, Y, et al. 2, 2002, Radiotherapy and oncology, Vol. 63, pp. 165-177. 4. Seppenwoolde, Y, et al. 3, 2000, International journal of radiation oncology Vol. 47, pp. 681-90 5. Shioyama, Y, et al. 5, 2007, International journal of radiation oncology Vol. 68, pp. 1349-1358.
Monday 1st September 2014, 09.00 – 10.30 Challenges in Medical Equipment Management
The software medical device: a review of regulations Cosgriff PS. Nuclear Medicine Department, United Lincolnshire Hospitals NHS Trust, Lincoln, UK. Email: [email protected] Until relatively recently there has been doubt whether some types of standalone software produced in medical physics / clinical engineering departments constitute a medical device under the UK Medical Device Regulations. The definition includes distribution as well as application, so software produced in-house for sole use within an NHS Trust is currently exempt from the requirements of the Regulations. However, the European Medical Devices Directives are currently being revised and this exemption is set to be removed.
Departments wishing to continue their software development activities will thus be required to implement a formal quality system in order to demonstrate compliance with the required parts of the Directive/Regulations. As is currently the case, departments wishing to distribute their software to other Trusts (or any other legal entity) will require full CE marking of the product, which requires the input of a Notified Body.
IEC 62304 has been recommended as the most suitable standard to use in this setting [1], but it does not cover all aspects of the software development process. Many other relevant standards exist and practical guidance will be given on which ones to use. Particular reference will be made to spreadsheet design, which is a burgeoning area within nuclear medicine as well as other areas of medical physics. In addition to the basic principles of the software design and testing, the presentation will also briefly cover the all-important writing of a departmental policy on in-house produced software, with reference to IPEM Report 86 [2] and its forthcoming revision.
1. IPEM Information and Computing Special Interest Group. Advice on the production and sharing of software as a medical device. IPEM Newsletter, November 2013. 2. Houston A, Cosgriff PS. Quality assurance of in-house developed software in nuclear medicine. In: Bolster A (Ed). Quality Control of Gamma Camera Systems. IPEM Report 86, IPEM, York, 2003.
Value – based Predictive Analytics & Optimisation in Scheduled Maintenance Prioritisation 1,2Akinluyi E, 1Ison K, 2Clarkson P J 1Medical Physics, Guy’s & St Thomas’ NHS Foundation Trust, London, UK. 2Engineering Design Centre, University of Cambridge, UK. email: [email protected] Background: It is vital to understand the basis on which various activities compete for resources – especially considering the increasing pressure to do as much as possible with limited money and manpower [2]. Our colleagues outside the device-management world have begun to see ‘Value’ frameworks as a crucial mechanism, for aligning competition with the interests of the patient and the healthcare system as a whole [1, 4]. In equipment management, where a variety of proactive and reactive maintenance tasks compete for attention [5], a Value and evidence-based decision methodology could provide powerful information when navigating the challenge of maintenance prioritisation, and can further our appreciation of the impact of non-patient-facing processes.
‘Value’ is a hypothetical quantity representing the desirability of various situational attributes, usually in reference to outcomes of a particular decision. It might be defined to include dimensions of risk, cost and benefit and a plethora of sub-dimensions. It is “a function of their relative importance” and emphasises how they trade off. Often the purpose of EBM (evidence-based maintenance) activities is to justify more efficient and cost-effective decisions, on the basis that they will not increase risk to the patient. In contrast, the Value approach to EBM frames resource allocation as an optimisation, and ideally includes a more holistic treatment of maintenance outcomes, including some indication of impact on clinical capacity.
Whereas current, clinical applications of the Value concept are not explicit in their methodologies - this paper presents a Value analytical framework and its specific application to the case study at King’s Health Partners, where predictive analytics of device field data, incident data, and clinical coding data were used to produce decision support. The frameworks and findings presented here have come about from a collaborative research effort, between King’s Health Partners, and the Engineering Design Centre, Cambridge University.
Methods: This study is structured around a Value based decision framework, which has been developed to combine quantitative models of clinical, physiological, technological and management processes, with organisational objectives. The quantitative models were informed by data mining & fusion, and predictive analytics of device-related data using Bayesian methods [3].
Results: ‘Estimated Marginal Value of maintenance’ curves were generated for a range of device models. These curves show the relationships between timing of maintenance and forecasted impact, in terms of various ‘Value dimensions’, including, cost, Δcapacity and harm (i.e. risk).
Discussion: These results show great promise in increasing our understanding of device maintenance. While the underlying data is of variable integrity, the methods used to re-structure and process the data using ‘predictive analytics’ effectively account for this and derive a ‘best estimate, given all that is known’, while simultaneously quantifying uncertainty. The Value framework also provides structured indications for the structure and quantity of data needed, to iteratively refine the analysis.
Conclusion: Since this is a ‘learning’ framework, with the integration of more data, this already-powerful analysis has the potential to become more informative. This framework has already drawn interest, for application in other, more clinical decisions.
Key references [1] Brook R H. “The End of the Quality Improvement Movement - Long Live Improving Value”. JAMA: The Journal of the American Medical Association, 2010. [2] Ham C. What will the Health and Social Care Bill mean for the NHS in England? BMJ, 2012. [3] Kipersztok O, Dildy G A. “Evidence-based Bayesian networks approach to airplane Maintenance”. Proceedings of the 2002 International Joint Conference on Neural Networks, 2002. [4] Porter M E. What is value in health care? New England Journal of Medicine, 2010b. [5] Wang B, Furst E, Cohen T, Keil O R, Ridgway M, and Stiefel R, “Medical Equipment Management Strategies,” Biomedical Instrumentation & Technology, May 2006.
Specifying 'Medical Technical Infrastructure' against Clinical Demand at a Neonatal Unit in Ndola, Zambia 1,2Akinluyi E, 3Chinkoyo S, 1Cheston V, 2Clarkson P J 1Guy’s & St Thomas’ NHS Foundation Trust, London, UK. 2Engineering Design Centre, University of Cambridge, UK. 3Ndola Central Hospital, Zambia. email: [email protected] Background: It could be said that the processes of medical equipment management involve the design of ‘MTI’ (Medical Technological Infrastructure) – That is, the design of “any and all factors and entities within a healthcare system, which have an impact on the capacity and capability to deliver ‘Value’ through the core function and externalities of Medical Technologies” [1].
A costly pitfall in equipment management (and particularly in medical device donation [3]), occurs where there is limited consideration of MTI factors. If, for example, a medical device is considered only at ‘face Value’, as embodying a procedural capability at a cost, it can be taken for granted that the device also embodies: consumable costs, maintenance labour costs, a patient safety liability, training requirements, storage requirements etc. Failure to consider these factors can render the device Value-less in a short time. Hence the need to carefully and deliberately design MTI.
As with any design problem, it is important to understand the need that is being addressed - i.e. the Value that we hope to generate. Although other factors come into play (see figure 1 below), MTI design is ideally driven primarily by clinical need.
Figure1: The Influence of External Factors, in Healthcare System Design [2]
This paper describes a study into how MTI requirements may be forecasted, based on quantitative analysis of clinical/procedural demand. Emphasis is placed on not only forecasting the quantity of devices required but also forecasting the required level of other MTI factors, such as technician and user training, maintenance provisions etc. This analysis is based on coded procedural records provided by collaborators’ from the neonatal care service at Ndola Central Hospital, Zambia.
Methods: This study is based on various modelling methods, applied to data gathered in Ndola over the course of two years. The data was coded and analysed for trends, to estimate a required level of procedural capacity.
Results & Discussion: While some of the modelling assumptions need to be tested, the analysis was sufficient to confidently direct service planning
Conclusion: Study of the data in this depth represents something of an ideal in how we go about planning services, but given the growing prevalence of clinically coded data here in the UK, there may be potential to implement such a methodology on a larger scale.
Key references [1] Akinluyi E, “Definition & Predictive Analytics of value in the Design of Medical Technological Infrastructure – PhD First Year Report,” Cambridge, 2013 [2] Akinluyi E, Ison K, Clarkson P J, “Designing for Value, Using Analystics of Medical Device Field Data,” International Design Conference, Dubrovnik, 2014 [3] Damman V, Pfieff H, Hospital Engineering in Developing Countries. Eschborn, Germany, 1986
Vital Signs Monitoring: why does the choice of device affect the measurement? 1Davie A, 2Amoore J N, 3Scott DHT 1Medical Physics, Royal Infirmary of Edinburgh, NHS Lothian; 2Medical Physics, NHS Ayrshire and Arran; 3Anaesthetics, Royal Infirmary of Edinburgh, NHS Lothian, Scotland. email: [email protected] Background: Traditional Pulse Rate (PR), Temperature (T) and Blood Pressure (BP) measurements have been joined by oxygen saturation (SpO2) as routine vital signs for clinical decision making. New methods of making these measurements have resulted in increasing concerns about measurement device-dependency (4). These variations are present even if the devices are working accurately and used correctly, which is not always the case (2, 8). Methods: The literature was reviewed to understand what affects the accuracy of vital signs measurements and their impact on clinical care, focusing on T, BP and SpO2. Early warning scores (EWS) combine these with respiratory rate, pulse rate and level of consciousness to assess patients, with trigger points to standardise response and action (6). Results: T: The ideal thermometer should be mercury-free, minimally invasive, quick, reliable, accurate, safe, and cheap, with minimal user-technique dependency. No devices meet these stringent criteria. Measurement variability, including operator dependency, can be compounded by the proprietary algorithms used, which may include offsets to convert, for example, temperature recorded from the ear to an oral equivalent (3). This can change EWS by 1 or 2 points. BP: EWS focus on systolic BP’s below 110mmHg, with each 10mmHg difference adding 1 to the score. Most BP measurements are now made with automatic sphygmomanometers whose algorithms are based on population averages that do not fully accommodate specific patient groups such as chronic renal disease and pre-eclampsia (1,2,4). Measurement accuracy is further compromised by inappropriate choice of cuff size (1). SpO2: Functional and fractional SpO2 measurements differ typically by about 2%. Measurements are also limited by device and sensor accuracy (within 2% to 3%, less accurate at lower saturations) and operator technique (5,7). Discussion and Conclusion: Vital signs measurements are a function of device characteristics, device usability and user-competence. The resulting variability can impact on clinical decision making. Device- dependency can have impacts when new equipment is purchased where device algorithms and user characteristics can alter numeric measurement readings in relation to existing EWS thresholds. The concern that a vital signs measurement device works well “except in critically ill patients” (8) presents challenges. For users to understanding the routine measurement technologies they rely on, to understand the device limitations and how to operate devices correctly. For procurers to understand what they are buying. For standards organisations to minimise device-dependency. For manufacturers to minimise operator measurement dependency. References 1. Amoore JN. Oscillometric sphygmomanometers: a critical appraisal of current technology. Blood Pressure Monitoring, 2012; 17(2): 80-88 2. Amoore JN, Davie A, Scott DHT. Routine Vital Signs: What are we measuring? BMJ 2013. http://www.bmj.com/content/346/bmj.f1747/rr/676003 3. Davie A, Amoore J. Best practice in the measurement of body temperature. Nursing Standard, 2010; 24(42):42-49. 4. Kaufmann etal. Oscillometric blood pressure measurements by different devices are not interchangeable. Anesthesia and Analgesia 1996; 82:377-381. 5. Milner etal. An assessment of the accuracy of pulse oximeters. Anaesthesia 2012: 67:396-401 6. Royal College of Physicians (2012) National Early Warning Score (NEWS): Standardising the Assessment if Acute Illness Severity in the NHS: Report of a Working Party. London: RCP. tinyurl.com/RCP-Early-warning 7. Valdez-Lowe C et al. Pulse oximetry in adults. AJN 2009, 109:52-59. 8. Vernon G. Medical devices Inaccuracy of forehead thermometers. BMJ 2013;346:f1747
Monday 1st September 2014, 09.00 – 10.30 Magnetic Resonance Scientific Session
Assessment of Longitudinal Changes in Contractile Function using DENSE in Patients with Myocardial Infarction McComb C1,2, Carrick D3, Woodward R2,4, McClure J2, Radjenovic A2, Berry C2,3, Foster J1,2 1Department of Clinical Physics, NHS Greater Glasgow and Clyde, UK, 2BHF Glasgow Cardiovascular Research Centre, UK, 3Department of Cardiology, Golden Jubilee National Hospital, Glasgow, UK, 4Department of Diagnostic Imaging, Golden Jubilee National Hospital, Glasgow, UK Email: [email protected] Background. Myocardial infarction (MI) causes dysfunction in the affected tissue, which can be assessed using DENSE (Displacement ENcoding with Stimulated Echoes) to quantify myocardial strain1,2. The aim of this study was to investigate changes in strain revealed by DENSE between the occurrence of MI and a 6 month follow-up. Methods. 50 male patients (age 56 10 years) underwent an MRI scan on a 1.5T Siemens Avanto within 7 days of MI, and 47 returned for a follow-up scan after 6 months. The protocol included DENSE and late gadolinium enhancement (LGE) imaging. DENSE and LGE were compared using a single mid-ventricular short-axis slice, which was divided into 6 segments for analysis3. DENSE images were analysed to obtain values for peak circumferential strain (Ecc) and strain rate. Segments in the baseline scans were categorised according to their proximity to LGE (remote, adjacent, infarcted). Measurements obtained at baseline and follow-up for each category individually were evaluated using Wilcoxon signed rank tests. A Kruskal-Wallis test with individual Mann-Whitney tests was then used to compare the differences in strain between baseline and follow-up for the three categories. The data were then further categorised according to the change in proximity category between baseline (B) and follow-up (FU) e.g. remote (B) remote (FU), adjacent (B) infarcted (FU) etc. Segments which were categorised as remote, adjacent and infarcted at baseline were considered separately, and the changes in strain between sub-categories (e.g. remote (B) remote (FU) vs remote (B) adjacent (FU)) were compared using a Kruskal-Wallis test with individual Mann-Whitney tests. A similar comparison between sub-categories was performed to assess if differences in strain measurements at baseline could be detected. Results. Diagnostic images were obtained for 50 and 43 patients at baseline and follow-up respectively. Statistically significant increases in strain were observed in both adjacent and infarcted segments. The results of the comparisons between changes in strain in remote, adjacent and infarcted segments are illustrated in Figure 1. For each category (remote, adjacent, infarcted), comparison of sub-categories showed no statistically significant differences in the changes in strain between baseline and follow-up. However, statistically significant differences between sub-categories were observed for strain measurements obtained at baseline for both adjacent and infarcted segments, as illustrated in Figure 2. Conclusions. Strain recovery was observed using DENSE in infarcted segments at 6 months post-MI, and also in segments which are adjacent to infarction. Strain measurements at baseline may have prognostic value relating to the progression or recovery of contractile abnormalities at follow-up. Key references. 1. J Magn Reson 1999; 137: 24 – 252, 2. Magn Reson Med 2012; 1590 – 1599, 3. Circulation 2002; 105: 539 – 542
Figure 1 Figure 2
A Fast Susceptibility Weighted Imaging MRI Sequence for Neonate Brain Scanning 1Fagan A J, 1Winston E., 1McLaughlin N., 2Boyle M., 2McCrudden T., 2Hoare S., 2Kelliher E., 2Ryan S., 3Browne J.E., 1Meaney J.F., 2Foran A. 1 National Centre for Advanced Medical Imaging (CAMI), St James Hospital / Trinity College Dublin, Ireland 2 The Children’s University Hospital, Temple Street & Rotunda Hospital, Parnell Square, Dublin, Ireland 3 School of Physics & FOCAS, Dublin Institute of Technology, Ireland Email: [email protected] Background: Susceptibility weighted imaging (SWI) produces image contrast in MR images based on local changes in magnetic susceptibility. First described over fifteen years ago, it has begun to appear on clinical MRI systems for applications in the detection of cerebral abnormalities in adults such as haemorrhages, vascular malformations, infarction and other traumatic brain injuries where the pathologies are intrinsically linked to localised changes in magnetic susceptibility (due to accumulations of iron or calcifications), rendering SWI a sensitive indicator [1-3]. A drawback of SWI is the relatively long acquisition time (typically 5-8 minutes) [4]. Few studies have described the use of SWI in neonates [5], where the long acquisition time is particularly problematic considering that patient compliance in remaining still for the duration of the scan is not guaranteed. The aim of this study was to compare the performance of a fast SWI acquisition scheme with that used conventionally in a clinical research study involving pre-term neonates. Methods: A novel SWI acquisition scheme was implemented on a 3T scanner (Achieva, Philips), using a 3D echo planar imaging (EPI) technique which reduced the acquisition time by 64% (to 1 min 42s) compared to the conventional spoiled gradient echo technique (SPGR – 4 min 42s). Both techniques were incorporated into a clinical research study involving 33 pre-term neonates investigating brain malformations due to intra-uterine growth restriction (ethical approval from the local REC). SW images were generated from both techniques and a randomised blinded clinical evaluation by three paediatric radiologists compared the resultant diagnostic image quality. Test phantoms were constructed to quantitatively compare the imaging performance of both techniques from a spatial resolution and contrast perspective. Results: Both SWI techniques were found to have comparable image quality, with similar levels of artefacts and microbleeds detected. The venous vasculature was more clearly visible with the new EPI-SWI technique, although its spatial resolution was slightly lower. Phantom contrast-to-noise and spatial resolution Comparison of SW images acquired with the new EPI measurements revealed similar technique (left) and the conventional SPGR technique contrast performance but slightly (right), showing improved visibility of vasculature and poorer spatial resolution for the EPI improved confidence in the diagnosis of a microbleed technique. (bottom right of images). Discussion: The EPI-SWI technique decreased the visibility of anatomical landmarks somewhat, however reading the SWI images alongside conventional T1-weighted or T2-weighted images, which would always be acquired in addition to SWI, was felt to overcome this problem. Conclusion: The EPI-SWI technique could replace the conventional SPGR-SWI technique in situations where microbleeds and/or vascular malformations are of primary interest and/or when the patient cannot remain still for long. Key references [1] EM Haacke et al, Magn Reson Med 52(3), 612-618, 2004. [2] JR Reichenbach, Neuroim 62(2), 1311- 1315, 2012. [3] EM Haacke et al, AJNR Am J Neuroradiol 30, 19-30, 2009. [4] J Seghal et al, J Magn Reson Imaging, 22(4):439{50, 2005. [5] A Meoded et al, Clin Radiol, 67(8), 793-801, 2012.
Validation and optimisation of 4D flow-sensitive MR imaging using an elastic vascular phantom. Awwad A, Pavlovskaya, Alley M, Auer D. Radiological and Imaging Sciences, Univ. of Nottingham, The United Kingdom. [email protected] Background: Phase Contrast Imaging (4D MRI) is a novel MRI sequence used in research to investigate the haemodynamics of blood flow. It offers a contrast free technique to obtain multi-directional velocity measurements with high spatial and temporal resolutions during the cardiac cycle. Recently, some significant studies have demonstrated the validity of 4D MRI in medium-large vessels regions (cardiovascular) as well as the circle of Willis (cerebrovascular). (1, 3) 4D flow MRI is capable of detecting the change in particles velocity and ultimately providing image contrast to demonstrate blood flow in vessels. It has been used effectively in the evaluation of cardiovascular haemodynamics of healthy/diseased aorta (atherosclerotic, coarctation and dissecting), cerebral arteries, carotids, arteriovenous malformations and congenital vascular abnormalities (2-5). Elastic Vascular Phantom: calibration of the 4D flow sensitive system response will be tested using a higher dynamic range will be performed by the use of an elastic (silicon) MRI-compatible model of the whole vascular tree (head-neck-thorax-abdomen) with simulation of pulse and aneurysmal disease. Methods: At our institution, temporally resolved 4D MRI phase contrast flow acquisition will be tested. It is acquired by the licensed 4D flow sequence, reconstruction software and post-processing analysis (GT Flow). Below are the MRI sequence details using a 3 Tesla GE 750 Discovery – 32 Channel Torso Coil (RT 4.848 - ET 1.932 - Spatial Resolution 1.25 - HR 80 - Flip Angle 15 - Scan time 6-9 min - Voxel size: 1.17 X 1.17 X 2-4 mm - Image matrix: 256 X 256 - FOV 300 X 300 X 96 mm - 20-24 Slices over 20 timestamps at 38-41 ms each = 722 - 820 ms per cardiac cycle. Using the elastic vascular phantom, flow and pressure gradient measurements will be compared and analysed for concordance with Doppler US assessment and gold-standard pressure sampling using an intravascular catheter and arterial line introduction in the phantom vascular tree. Results: Current study in progress to obtain final and confirmatory data for concordance analysis.
Discussion. Characteristically, state of the art 4D flow MRI can utilize ECG gated + Respiratory compensatory techniques to synthesize time-resolved flow-sensitive data which is regarded as a dynamic assessment of 3D PCI in real-time (hence the 4th dimension). Currently investigated techniques including our proposed sequence tested using pulse emulation to enable sampling of the haemodynamic parameters at a temporal resolution of 25-30 Hertz in a relatively short scanning time (average scanning time 7 - 15 minutes per anatomical region). Therefore, this emerging MRI technique has great translational potential in providing in vivo visualisation and quantification of blood flow during clinically acceptable examination times. Conclusion: As a crucial part of a major qualification study at our centre, the current work is proposed to investigate the haemodynamic changes of the measured flow parameters and derived relative pressure estimates within the abdominal or thoracic aorta in aneurysmal disease. This novel imaging sequence will be used to generate continuous and categorical individualised haemodynamic parameters in an attempt to identify promising biomarker associated with patient survival and aneurysm growth. Additionally, it has the advantage of providing a visual and quantitative new insight into the rheological properties and disturbances of healthy and diseased vessels. Key references: 1. Wentland, A.L., T.M. Grist, and O. Wieben, Repeatability and internal consistency of abdominal 2D and 4D phase contrast MR flow measurements. Acad Radiol, 2013. 20(6): p. 699-704. 2. Markl, M., P.J. Kilner, and T. Ebbers, Comprehensive 4D velocity mapping of the heart and great vessels by cardiovascular magnetic resonance. J Cardiovasc Magn Reson, 2011. 13: p. 7. 3. Markl, M., et al., Analysis of pulse wave velocity in the thoracic aorta by flow-sensitive four dimensional MRI... J Magn Reson Imaging, 2012. 35(5): p. 1162-8. 4. Strecker, C., et al., Flow-sensitive 4D MRI of the thoracic aorta: comparison of image quality, quantitative flow, and wall parameters at 1.5 T and 3 T. J Magn Reson Imaging, 2012. 36(5): p. 1097-103. 5. Delles, M., et al., Estimation of aortic pressure waveforms from 4D phase-contrast MRI. Conf Proc IEEE Eng Med Biol Soc, 2013. 2013: p. 731-4.
GTFlow© Software: http://www.gyrotools.com/products/gt-flow.htm Vascular Phantoms (Elastrat): http://www.elastrat.com For details of project’s IPEM award: http://www.ipem.ac.uk/Newsletter/Dec_13/Othernews.aspx
Monday 1st September 2014, 11.00 – 12.00 Biennial Radiotherapy Physics Conference – Brachytherapy
Auditing HDR brachytherapy physics in the UK 1Palmer A L 1Radiotherapy Physics, Medical Physics Dept, Portsmouth Hospitals NHS Trust, UK. email: [email protected]
The reassurance that treatment is being delivered in line with accepted standards, that delivered doses are as prescribed, that opportunities for quality improvement are taken, and that quality control practices are optimised, is a fundamental requirement in radiotherapy. This is as essential for brachytherapy as it is for the more commonly audited and reviewed external beam radiotherapy [1]. Unfortunately, dose measurement in brachytherapy is challenging due to steep dose gradients and small scales, especially in the context of an external audit.
After a brief review of errors in brachytherapy, to set the scene, this presentation will discuss the concept of dosimetric audit and the recent resurgence of brachytherapy audit activity in the UK, benefiting from 4 complementary audits being conducted in the UK during 2014. The presentation will focus on the recently completed IPEM-sponsored BRachytherapy Applicator Dosimetry (BRAD) audit, which comprised an end- to-end system check of planned and delivered dose distributions around clinical brachytherapy applicators at every brachytherapy centre in UK [2]. The test object is now available via the IPEM virtual phantom library. Recommendations for film dosimetry techniques as used for the audit will be discussed [3]. Observations on the diversity of brachytherapy-physics practice encounter during the audits will be mentioned, with a few suggestions for improvement.
In line with the brachytherapy audit theme, the presentation will also include a brief review of an audit of brachytherapy quality control practice that was conducted recently in the UK, identifying areas of consensus and variance.
[1] Palmer AL, Bradley D, Nisbet A. Dosimetric audit in brachytherapy. Br. J. Radiol. (published online ahead of Print, pp. 20140105 http://dx.doi.org/10.1259/bjr.20140105)
[2] Palmer AL, Lee C, Ratcliffe AJ, Bradley D, Nisbet A. Design and implementation of a film dosimetry audit tool for comparison of planned and delivered dose distributions in high dose rate (HDR) brachytherapy. Phys. Med. Biol. 2013;58:6623-6640
[3] Palmer AL, Bradley D, Nisbet A. Evaluation and implementation of triple-channel radiochromic film dosimetry in brachytherapy. J. Appl. Clin. Med. Phys. (in press)
Characterisation of well chamber response to various I-125 cartridge positions and orientations 1Leydon P, 1Dooley C, 1Woulfe P 1Department of Medical Physics, The Galway Clinic, Galway, Ireland email: [email protected] Background: The permanent transperineal interstitial placement of I-125 seeds is a popular choice for Low Dose Rate Brachytherapy for Prostate Cancer. The deposited-seed positions are imaged and the plan optimized in real-time throughout the procedure. In order to provide effective treatment, the determination of the air kerma strength of a radioactive seed is necessary. Typically, well-type ionization chambers having calibrations traceable to national standards are used to independently determine the air kerma strength of seeds for quality assurance practices. This short study examined the impact that various cartridge measurement set-ups had on well chamber response and on calculated air kerma strengths. Methods: The response of the well chamber was tested by placing seed cartridges in a variety of positions and orientations within the well camber as well as in the cartridge holder itself. The positions and orientations were selected in order to examine the chamber’s axial response and angular dependence. The attenuating effects of the cartridge holder itself and a possible gross set-up error (cartridge inverted in holder) were also examined.
Fig 1 above left shows the various cartridge positions A, B, C & D that were examined, including an upside down position E. Fig 2 above right shows the experimental set-up for determining the chamber’s axial response. Results: The effect of angular dependence and holder attenuation on air kerma was found to be quite small. The well chamber displayed strong axial dependence as outlined in the manufacturer’s specifications. By placing the cartridge in an inverted position in the holder the source is no longer at the chamber “sweet- spot” and the axial response becomes prominent. The variation observed between readings for the same cartridge set-up was also identified as a possible potential for errors.
Fig 3 above left shows the response various cartridge positions A, B, C, D & E. Fig 4 above right shows chamber’s axial response. Discussion: The calculation of apparent activity involves a number of correction factors. Periodic verification and counter checking of the calculation may be important in order to avoid introducing a systematic error which could go un-noticed. For example, if an incorrect unit for pressure was used (mbar instead of torr) and the cartridge was in an inverted position the errors cancel out and the user would be unaware their set-up is incorrect. Conclusion: The biggest potential error may arise if a user was unfamiliar with the correct method of placing the cartridge in the holder and it was placed in an inverted position. This leads to decreased chamber sensitivity of a few percent, resulting in deviations from the specified manufacturer’s air kerma value. The variation observed between measurements of a cartridge with the same experimental set-up was interesting as it demonstrated that there is an inherent uncertainty in the chamber which is comparable to many the errors introduced in experiments.
Comparison of a single fraction HDR Brachytherapy to single fraction SABR with a simulated prostate-rectal space for localised prostate cancer 1,2McGarry CK, 3Ravi A, 1Kanakavelu N, 2McMahon SJ, 1,2O’Sullivan JM, 1,2Hounsell AR, 3Loblaw A, 1,2Jain S. 1Northern Ireland Cancer Centre, Belfast, UK. 2Centre for Cancer Research and Cell Biology, Queen’s University, Belfast, UK. 3Sunnybrook Odette Cancer Centre, Toronto, Canada email: [email protected] Background. For Ca.Prostate, hypofractionated treatment has the advantage that the prostate has a low alpha-beta ratio. A single fraction dose between 19 Gy and 20 Gy, irrespective of the delivery technique, has been reported to be radiobiologically optimal3. Interstitial high dose rate brachytherapy (HDR-BT), with its excellent conformal dose delivery, stands as the best treatment option. Stereotactic ablative radiotherapy (SABR), with hypofractionated conformal delivery, can be considered for patients who cannot undergo general anaesthesia. Multiple planning studies comparing SABR and HDR-BT have been reported1,2. SABR can achieve target doses equal to that of HDR-BT, but the limiting factor is the rectal dose due to the additional set-up margin for the target. Data are emerging on the use of hydrogel spacers placed between the prostate and rectum to reduce rectal doses4,5. A planning study is presented that compares Trans rectal ultrasound (TRUS) based HDR-BT plans to SABR plans for 20 Gy in a single fraction. Methods. A dataset of five patients was used to compare HDR-BT and SABR plans. For all 5 patients, HDR-BT plans were created on TRUS images with an anatomy based inverse planning method. Each patient also had a CT based SABR plan created using a single 10MV flattening filter free (FFF) arc with a uniform PTV of margin 5mm except for a 3mm margin towards the rectum. For all patients, two additional SABR plans were created to achieve intra-prostatic dose equal to that of HDR-BT with heterogeneous dose distributions. A space between the prostate and the rectum was simulated by translating the rectal structure so that the prostate-rectum separation was either 7.5mm or 10mm. Plans were assessed using the dose to 2cc of the rectum and 0.1 cc of the urethra. Each SABR plan was normalized so that the volume of target irradiated by the prescription dose was the same as the corresponding HDR-BT plan.
Results. The mean±SD of compared criteria for 5 patients are tabulated: Criteria HDR SABR SABR heterogeneous PTV Conformal Non-conformal V98%, % 97.8±1.1 98.8±0.88 98.9±0.7 98.8±0.9 V125%, % 66.4±5.0 0 54.4±1.8 62.2±1.2 V150%, % 35.5±3.4 0 22.9±2.3 33.4±4.7 V200%, % 11.5±2.1 0 1.9±1.8 4.6±1.5 Conformity Index 1.29±0.1 1.19±0.04 1.30±0.1 1.52±0.11 Rectum D2cc, Gy Original 9.0±0.5 12.2±2.5 12.1±2.6 11.8±2.7 Spacer7.5 - 9.3±0.9 9.1±1.3 8.9±1.4 Spacer10 - 8.0±0.9 7.8±1.3 7.6±1.4 Urethra D0.1cc, Gy 23.3±0.2 20.4±0.2 20.2±0.4 20.1±0.3 PRV 3mm - 20.9±0.3 22.5±0.4 22.2±0.7 Discussion. Intra-prostatic doses were significantly higher for HDR-BT than SABR. When the SABR plans were optimised to achieve intra-prostatic dose equivalent to that of HDR-BT, the plans lost their conformity. The rectal doses were higher in SABR. With the rectal space of 7.5 mm and 10 mm, SABR rectal 2 cc dose were comparable to that of HDR-BT. Urethral doses were lower for SABR in comparison to HDR-BT. Conclusion. SABR could be utilized in patients not suitable for HDR-BT, with similar minimum target dose and rectal dose achieved when a prostate-rectal space is employed. Key references. 1) Fuller DB et al. Int J Radiat Oncol Biol Phys. 2008;70(5):1588-97, 2) Hermesse J et al. Strahlenther Onkol. 2009;185(11):736-42, 3) Mavroidis P et al. Int J Radiat Oncol Biol Phys. 2014;88(1):216-23, 4) Pinkawa M et al. Radiother Oncol 2013 106:220-224, 5) Song DY et al. Int J Radiat Oncol Biol Phys. 2013;87(1):81-7.
Monday 1st September 2014, 11.00 – 12.00 Trainee Session II
Evaluation of 4D PC-MRI as a tool for the quantification and visualisation of peripheral arterial flow in small vessels Authors: Hall Barrientos P1, K. Lanaghan2, C. McComb3, T. Steedman2, K. Forbes4, J. Foster3, A. Watson1; 1Clinical Physics, NHS Greater Glasgow and Clyde, Glasgow, UK 2MRI, BHF Glasgow Cardiovascular Research Centre, Glasgow, UK 3Clinical Physics (MRI), BHF Glasgow Cardiovascular Research Centre, Glasgow, UK 4Institute for Neurological Sciences, Southern General Hospital, Glasgow, UK email: [email protected] Background. The visualisation of complex vascular structures and flow patterns has been the focus of much of the research on time resolved three-dimensional PC-MRI, known as 4D flow(1). However, the ability to obtain a volume of time resolved velocity data offers an exciting analogue to the use of colour and spectral Doppler ultrasound in vascular diagnosis. 4D Flow methods have their origins in cardiac and large vessel imaging but smaller vessels with their sensitivity and resolution represent a challenge for this new method. This study aimed to evaluate a 4D flow work-in-progress package as a potential tool for the quantification and visualisation of vascular blood flow within the carotid bifurcation. Methods. All MRI studies were performed on a 3T Siemens Verio and were cardiac gated. A 4-D flow dataset was acquired and analysed using a work-in-progress package supplied by Siemens. Standard 2D PC-MRI slices were also acquired. MRI scan parameters were optimised to obtain best spatial resolution within the temporal resolution constraints. For some studies the 3D velocity encoding parameter was varied between spatial dimensions. Test phantoms consisted of a computer controlled silicone-elastomer carotid vessel embedded in PVA gel with a 70% stenosis of the proximal ICA and a rigid silicone 8mm diameter tube with a 50% stenosis. The carotid arteries of two healthy volunteers were scanned. Optimisation of the MRI parameters was investigated for one of the volunteers and the utility of the 4D Flow analysis of those data sets was investigated. A reproducibility study was performed on both phantom and the two volunteers. Results. Both the test phantom and the in-vivo studies revealed that PC-MRI techniques underestimated the degree of stenosis, particularly for 4D flow. PC-MRI derived velocities would underestimate the degree of stenosis as defined by the consensus criteria for carotid Doppler scanning(2). The 50% stenosis phantom was better able to resolve the stenosis due to a higher pixel per lumen ratio and both 2D and 4D PC-MRI velocities were within the consensus criteria for 50% stenosis. 4D flow visualisation of these smaller vessels was difficult, due to limited spatio-temporal resolution constraints, but appeared to improve by reducing velocity sensitivity in the non-dominant flow directions. The flow, area, velocity and pressure waveforms from 4D flow analysis were assessed. Preliminary studies indicate good reproducibility between different scans in phantom and volunteer studies. Conclusion. The software shows promising results for the assessment of ICA stenosis and related hemodynamic changes. References. (1) Markl M, et al. 4D flow MRI. J Magn Reson Imaging 2012; 36(5):1015-1036. (2) Oates CP, et al. Joint recommendations for reporting carotid ultrasound investigations in the United Kingdom. Eur J Vasc Endovasc Surg 2009; 37(3):251-261.
Characterisation of Molecular Subtypes of Breast Cancer Using MRI 1Priba L, 1Waugh S, 2Vinnicombe S 1Medical Physics, NHS Tayside, Dundee, UK. 2Division of Cancer Research, University of Dundee, Dundee, UK email: [email protected]
Background. Breast cancer remains one of the most commonly diagnosed cancer in women in the UK, with around 50 000 women diagnosed with each year [1]. As with many other cancers, breast cancer prognosis depends on the type and stage of the cancer and treatment options are generally targeted to the specific type of cancer based on its characteristic receptor status. The aim of this work was to investigate morphological and functional MRI parameters to characterise differences between triple-negative (TNBC), HER2-positive (HER2) and Luminal (Lum) molecular subtypes of breast cancer.
Methods. Pre-treatment MRI scans for a total of 73 patients with biopsy-proven invasive breast cancer were analysed. Signal intensity values for whole lesion were measured by drawing regions of interest (ROIs) on T2- weighted images and the 2-minute post-contrast injection Dynamic Contrast-Enhanced (DCE2min) subtracted images. Apparent Diffusion Coefficients (ADC) were measured on maps produced from diffusion images acquired with b=50 and 800 s/mm2. For each parameter, percentage tumour heterogeneity was calculated as the ratio of standard deviation and mean signal intensity/ ADC. MRI parameters were compared using one-way analysis of variance (ANOVA) with Bonferroni-adjusted multiple comparisons.
Results. Significant differences were found for whole tumour ADC values and DCE2min heterogeneity. Post-hoc analysis identified that these differences were between TNBC (mean ADC=1.12x10-3mm2/s) and Lum (mean ADC=0.93x10-3mm2/s) lesions. Mean tumour ADC values were found in line with values reported in a recent study [2]. No significant differences were seen for T2-w or DCE2min signal intensities. For tumour heterogeneity as measured on DCE2min, TNBC lesions were found to have significantly higher heterogeneity (23.8%) compared to HER2 (15.8%) and Lum (16.5%). In addition, it was also noted that significantly more TNBC lesions formed a restricted diffusion rim compared with the other molecular subtypes (p=0.02), however this requires further investigation due to the small sample size of lesions with this characteristic.
Conclusions. TNBC lesions were found to have higher mean ADC values and lesion heterogeneity as seen on 2-minutes post contrast injection DCE images, when compared to other considered subtypes of breast cancer. TNBC tends to be higher grade, and more aggressive lesions. Previous work using texture analysis have identified these lesions as being more heterogenous [3], however this work suggests a more simple ROI- based measure may also provide meaningful results. Higher measured ADC values for TNBC compared with Luminal cancers could potentially be due to necrotic cores and these findings are in line with other studies within the literature [2]. The combination of these measures could be useful for non-invasive discrimination between TNBC, HER2 and Luminal lesions.
Key references. [1] Cancer Research UK, [Online]. [Accessed 24 April 2014]. Available from: http://www.cancerresearchuk.org/cancer-info/cancerstats/types/breast/ [2] Youk, JH et al. Eur Radiol. (2012); 22(8): 1724-1734 [3] Ahmed A et al. JMRI (2013); 38: 89-101
Investigating the accuracy and feasibility of calculating dose distributions in Cone Beam Computed Tomography for Adaptive Radiotherapy Ntentas G, King's Health Care Partners, London, UK Email: [email protected] Objectives: To quantify the variation of Hounsfield Units (HU) with changing cone-beam computed tomography (CBCT) scanning parameters and assess the feasibility of calculating dose onto CBCT for the purpose of adaptive radiotherapy (ART) and develop a method to be applied in clinical practice.
Materials and Methods: The Elekta XVI CBCT system and various phantoms were used to evaluate HU variation with changing scanning parameters such as tube voltage (kV), tube current (mAs) and field of view as well as with phantom size and craniocaudal position. Hounsfield unit to electron density (HU-ED) curves were produced and compared against the treatment planning CT curve. Preliminary calculations using Tissue Maximum Ratio (TMR) data were performed to assess the effect of HU variation on dose calculation. A patient data derived mutual information M-I technique was used to generate a H&N specific HU-ED calibration curve for CBCT. IMRT treatment plans were recalculated onto CBCT in the Monaco® treatment planning system by assigning both M-I and planning CT HU-ED curves. Resulting dose distributions were compared using 2D gamma analysis (3%/3mm). To increase the accuracy of dose distribution comparison, an anthropomorphic H&N phantom was developed and the same intercomparison method was followed.
Results: In general, inserts with nominal HU>0 were more sensitive to scan parameters, phantom size and position compared to low density materials (HU<0). HU variation caused unacceptable dosimetric errors when the CT curve was assigned for dose calculations on CBCT. For scans acquired with small FOV the dose was calculated more accurately when the M-I curve was used instead of the CT curve, gamma analysis pass rates were 97% and 89% respectively. For phantom H&N CBCT scans acquired with medium FOV the CT curve gave better dosimetric agreement than the M-I curve (97.6% and 93.2% respectively).
Conclusion: This research demonstrates the potential of using the CBCT datasets to accurately calculate doses and perform H&N ART treatment planning. To enable accurate dose calculation on CBCT, individual HU-ED curves should be developed for each treatment site and scanning protocol. Developing a new ART method that utilises calculated dose in CBCT was the main objective of this project. This new method will be proposed and compared with the currently used method at Guy’s and St Thomas’ hospital. To improve the ART workflow, the accuracy of dose calculation on patient CBCT scans when using medium FOV should be investigated. An atlas based method for generating planning structures in order to generate dose-volume- histograms for plan comparison during ART must also be investigated to improve workflow and allow improved ART decision making.
Keywords: Adaptive Radiotherapy, CBCT, CBCT dose calculation, CT number uncertainty.
Investigating the dosimetric effects of thoracic motion on volumetric modulated arc therapy treatments 1Moran L, 1Cowen M, 1Radiotherapy Physics department, Barts Hospital, London, UK. email: [email protected] Background. Volumetric modulated arc therapy (VMAT) is a delivery technique that involves complex beam apertures produced by dynamically moving MLC’s and variable dose rates during gantry rotation to achieve highly conformal dose coverage to a planned target volume (PTV). It has been well documented that there is potential for a reduction in delivered dose due MLC interplay effects during both IMRT and VMAT delivery to a target undergoing thoracic motion. (1)(2)(3) The aim of this work is to investigate and quantify this MLC interplay for VMAT plans of varying complexity and also different breathing traces. Methods. A lung tumour volume and relevant organs at risk were outlined in a CIRS dynamic thorax phantom. A conformal plan and a number of VMAT treatment plans of varying complexity (as defined by the number of MU’s) were created using Eclipse v11 treatment planning software. Each plan achieved at least 99% coverage of the PTV with 95% of the prescribed dose of 55Gy/20f, as per standard department protocol. The plans were delivered to the CIRS phantom, which was programmed with a recorded breathing trace to move the tumour 20mm (+/-10mm) in the superior-inferior direction. The delivered dose distribution was analysed using GAFCHROMIC film. Results. As expected, treatment delivery in the presence of breathing motion caused a reduction in PTV dose coverage in all cases. No significant differences in dose distribution were found between conformal or VMAT plans of varying complexity. Table 1 shows that breathing motion was observed to cause an approximately 2.4mm reduction in 95% isodose coverage at both superior and inferior ends of the PTV. Conformal VMAT 1 VMAT 2 VMAT 3 Monitor Units (MU’s) 372 521 802 899 95% isodose to PTV distance (mm) 2.3 2.4 2.3 2.5 Table1. The measured effect of breathing motion on 95% dose coverage in the sup-inf plane for four equivalent lung plans Discussion. In this case it was found that thoracic motion had little or no effect on the change in PTV dose coverage between conformal and VMAT plans of varying complexity. The effect of MLC interplay in VMAT for moving targets has been conflictingly reported in the literature both to have a potentially significant (1)(2) and also insignificant (4) effect on dose distribution. Further investigation of the variables that can effect VMAT treatments to the thorax is therefore required. Conclusion. This work will help to guide department protocol on the decision to treat thoracic cases using VMAT and will also assist in the formation of CTV-PTV margins for lung cases. Further work is underway that demonstrates the effect of varying tumour motion, tumour location and plan complexity for VMAT in the thoracic treatments. Key references. 1. Effects of Lung tumor motion on delivered dose distribution during RapidArc treatment technique. R. Boopathy, et al. 3, s.l. : Journal of Medical and Biological Engineering, Jan 2010, Vol. 30. 189 - 192. 2. Evaluation of breathing interplay effects during VMAT by using 3D gel measurments. S. Ceberg, et al. 7th International Conference on 3D radiation dosimetry : Journal of Physics: Conference Series 444, 2013. 3. P. J. Keall, et al. The management of respiratory motion in radiation oncology report of AAPM Task Group 76. 2006. 4. Dosimetric impact of breathing motion in lung Stereotactic Body Radiotherapy Treatement using Image- Modulated Radiotherpay and VMAT. M. Rao, et al. 2, s.l. : Journal of Radiation Oncology, Biology, Physics., 2012, Vol. 83.
Monday 1st September 2014, 11.00 – 12.00 Innovation in Physiological Measurement Services
Machine learning for mobile monitoring Clifton D A, University of Oxford Email: [email protected] Healthcare systems world-wide are entering a new, exciting phase: ever-increasing quantities of complex, massively multivariate data concerning all aspects of patient care are starting to be routinely acquired and stored, throughout the life of a patient, and increasingly involving mobile settings.
This exponential growth in data quantities far outpaces the capability of clinical experts to cope, resulting in a so-called “data deluge” in which mobile data are largely unexploited. There is huge potential for using advances in machine learning methodologies to exploit the contents of these complex mobile datasets by performing robust, scalable, automated inference to improve healthcare outcomes significantly by using patient-specific probabilistic models, a field in which there is little existing research, and which promises to develop into a new industry supporting the next generation of mobile healthcare technology. Data integration across spatial scales, from molecular to population level, and across temporal scales, from fixed genomic data to a beat-by-beat electrocardiogram, will be one of the key challenges for exploiting these massive, disparate mobile-associated datasets.
This presentation aims to describe the urgently-needed interaction between machine learning and mobile healthcare technology. We demonstrate how advances in machine learning for healthcare (or “computational health informatics”) can cope with the noise and artefact typically present in mobile-acquired datasets, and how, perhaps for the first time, the resulting fruits of mobile monitoring can be used within clinical practice to improve patient outcomes.
Novel combined optical spectroscopy and tissue oxygenation assessments of patients with systemic sclerosis - a pilot study 1,3Allen J, 1,3Di Maria C, 1,3Murray A, 2Ottewell L, 2Griffiths B 1Microvascular Diagnostics, Regional Medical Physics Department, and 2Department of Rheumatology, Freeman Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK. 3Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, UK. email: [email protected] Background. Patients with systemic sclerosis (SSc) can experience significant morbidity and mortality [1]. The development of methods to aid early diagnosis is very important [4, 5]. The aim of this pilot study was to assess the classification performance of combined optical non-invasive skin fluorescence spectroscopy [2] and tissue oxygen spectrophotometry [3] measurements in SSc.
Methods. Two groups, comprising 14 SSc patients and 9 control subjects, were included in the study. Fluorescence and tissue oxygen measurements were collected from 3 sites (chest, arm and leg). Fluorescence intensities at wavelengths attributed to collagen, elastin and L-tryptophan [2] were extracted from each site Excitation Emission Matrix (EEM) and a Fluorescence Score formed using site averaging ((Elastin+Collagen)/Tryptophan, dimensionless). Tissue oxygen saturation values from the same three sites were also averaged (giving Tissue Oxygenation, %).
Figure 1. Example fluorescence spectroscopy excitation emission matrix (EEM) plot from the skin.
Results. Overall patients with SSc had increased Fluorescence Scores and reduced Tissue Oxygenation when compared to controls. An experimental linear cluster separation produced an overall classification accuracy of 95.6%. Summary. The results of this pilot study demonstrate the potential diagnostic utility of these two novel ‘optical biopsy’ methods in patients with systemic sclerosis. Further validation work is being undertaken. Key references. 1. ACR Preliminary criteria for Systemic Sclerosis. Subcommittee for scleroderma criteria of the American Rheumatism Association Diagnostic and Therapeutic Criteria Committee. Preliminary criteria for the classification of systemic sclerosis. Arthritis Rheum 1980;23:581-590 2. DaCosta RS, Andersson H, Wilson BC. Molecular fluorescence excitation-emission matrices relevant to tissue spectroscopy. Photochemistry and Photobiology 2003:78;384-392 3. Harrison DK, Newton DJ, McCollum PT, Jain AS. Lightguide spectrophotometry for the assessment of skin healing viability in critical limb ischaemia Adv Exp Med Biol 1996;388:45-51 4. Murray AK, Moore TL, Manning JB, Griffiths CEM, Herrick AL. Noninvasive measurement of skin autofluorescence is increased in patients with systemic sclerosis: An indicator of increased glycation endproducts? J of Rheumatol 2012 39:1654-8 5. Steen VD, Medsger TA. Improvement in skin thickening in systemic sclerosis associated with improved survival. Arthritis Rheumat 2001;44:2828-2835
Monday 1st September 2014, 11.00 – 12.00 General Imaging Scientific Session
Development of an optimized Doppler sensitivity testing protocol for assessing fit-for-purpose early pregnancy ultrasound systems 1Browne J E, 2Cournane S, 3Fagan AJ 1School of Physics & FOCAS Institute, Dublin Institute of Technology, Ireland. 2Medical Physics and Bioengineering, St James’s Hospital, Ireland. 3Centre for Advanced Medical Imaging, St James’s Hospital & Trinity College Dublin, Ireland. email: [email protected] Background. Foetal cardiac activity is well documented as the earliest proof of a viable pregnancy and, thus, ultrasound imaging, particularly Doppler imaging using a transvaginal (TV) probe, has become the main diagnostic means of examining the health and development of the foetus (Blaas et al., 1995; Jauniaux et al., 2005; Mitra et al., 1996). For an embryo of gestational age of typically greater than 6 weeks, a lack of cardiac activity after 30 seconds of imaging is regarded as a primary diagnosis of foetal demise (Condous et al., 2003). While the clinical need for high quality performance foetal imaging has been emphasized, no specific medical physics quality assurance (QA) guidelines, in particular no Doppler performance test for foetal ultrasound systems have been established. The objectives of this study were to develop a technical measure of Doppler sensitivity performance using a commercially available flow phantom and to compare the results with a previously established Doppler Sensitivity Performance Index using an in-house developed flow phantom (Browne et al 2004). Methods. The technical evaluation of Doppler sensitivity was evaluated using both the Mini-Doppler Flow Phantom (Gammex-RMI) and an in-house built Doppler sensitivity flow phantom. Both flow phantoms had two vessels (Mini-Doppler and In-House Flow phantom had vessels ranging from 1.6 and 4.8 mm) at depths from 2 – 15 cm and a lowest achievable velocity of 24cm/s and 0.5 cm/s, respectively. In this study the Doppler sensitivity and detectability for a range of ultrasound machines was evaluated using both flow phantoms. The Doppler detectability was defined as the deepest signal which could be detected free from extraneous noise in the presence of clutter (e.g. an overlying fat layer or a low frequency (kHz) sound source). Results. Differences in Doppler sensitivity performance between the ultrasound scanners could be demonstrated using the DSPI, with the Siemens Antares demonstrating the best Doppler sensitivity while the Siemens Acuson Aspen had the poorest Doppler sensitivity performance of this group.
Comparison of the Doppler Sensitivity Performance Index of each of the U/S Scanners @ 2 - 4MHz 35 30 Aspen 25
20 Antares 15 10 HDI 5000 5
0 "SensitivityPerformance Index" Power Doppler Colour Doppler
Further, results of both Doppler Sensitivity and Detectability will be presented for a range of ultrasound systems used for the identification of early pregnancy foetal heartbeat. Also, a protocol for assessing Doppler detectability using a commercial flow phantom will be presented.
Discussion and Conclusion. The Doppler Sensitivity Performance Index can provide good differentiation between different machines of different class but more importantly of similar class which would be useful in identifying Doppler ultrasound machines which could be used for detecting early pregnancy foetal heart beat. Key references. Blaas HG et al., Ultrasound Obstet, Gynecol. 6, 240-249 Browne JE et al., Ultrasound in Med. & Biol., Vol. 30, No. 11, pp. 1475–1483, 2004 Condous G et al., Ultrasound Obstet Gynecol 2003; 22: 420–430 Jauniaux E., et al., Ultrasound Obstet Gynecol; 25: 613–624 Mitra AG, et al., Am J Obstet Gynecol. 175(1):41-4.
Objective evaluation of breast ultrasound image quality with clinically-relevant contrast detail phantoms 1Cournane S, 2Fagan AJ, 3Browne JE. 1Dept of Medical Physics & Bioengineering, St James’s Hospital, Dublin 8, Ireland. 2Centre for Advanced Medical Imaging, St James’s Hospital/Trinity College Dublin, Ireland. 3Medical Ultrasound Physics and Technology Group, School of Physics & FOCAS Institute, Dublin Institute of Technology, Kevin Street, Dublin 8, Ireland. email: [email protected] Background. Breast Ultrasound scanners are used to distinguish lesions of varying size and subtle contrast from background tissue and, thus, low contrast and anechoic target detectability tests, for this speciality, are regarded as the most relevant performance indicators [1,2]. Current commercially-available ultrasound phantoms commonly used for breast imaging quality assurance (QA) typically contain cylindrical grey scale targets embedded in uniform tissue mimicking backgrounds; however, these designs do not adequately replicate the complex nature of breast tissue. Further, their sizeable target inserts combined with a broad range of contrast values do not sufficiently challenge high frequency breast ultrasound scanners [3]. This study presents the image quality evaluation of a number of breast ultrasound systems using novel contrast detail phantoms of finely-sized spherical anechoic and contrast lesion targets, offering a clinically-realistic imaging challenge. Methods. Phantoms with anechoic and low contrast (-1 to -4dB) cylindrical and spherical lesion targets, of a range of diameters (1 – 4mm) and depths (10 – 55mm), were constructed, with the background tissue- mimicking material exhibiting an acoustic velocity and attenuation coefficient of 1540m/s and 0.5dB/cm/MHz, respectively. The phantoms displayed a linear relationship between attenuation and frequency at high frequencies (up to 20MHz) [4]. The test objects were used to measure the Lesion Contrast-to-Noise Ratios (LCNR) for a range of modern breast-specific ultrasound scanners including high- end and mid-range systems. LCNR calculations were achieved through analysis of DICOM phantom images using a semi-automated Matlab® program. Results. In the case of the anechoic cylindrical lesion targets, all scanners showed a comparable image quality performance; however, the spherical lesions provided a means of not only differentiating between high and mid-range scanners but also between the high-end breast-dedicated scanners. Only the very high frequency systems were capable of resolving the 1mm anechoic spherical targets measuring while all high- end scanners were capable of imaging the 2 - 4mm lesions located within the systems’ penetration depths, albeit with differing LCNR values. The subtler spherical contrast detail lesion targets, specifically the -2dB targets, were not detectable for the mid-range systems evaluated. Discussion. The spherical lesion phantom offered a sensitive means of assessing imaging quality performance of breast-specific ultrasound systems with the 2mm low contrast spherical lesions best challenging the high-end scanners, while proving undetectable for mid-range scanners. Conclusion. This study presents a novel means of measuring, and tracking, image quality performance for ultrasound systems where only a subtle difference between the ultrasonic characterisation of normal tissue and malignancy may exist, a difference not challenged by commercially-available phantoms. Key references. 1. Kofler, Jr. JM, et al., Ultrasound in Med. & Biol., 2005, 31(3) pp 351-359. 2. Kofler, Jr. JM, et al., Ultrasound in Med. & Biol., 2001, 27(12) pp 1667-1676. 3. Browne J. et al., Ultrasound in Med. & Biol., 2005, 31(7), pp 957-964. 4. Cannon L. et al., Ultrasound in Med. & Biol., 2011, 37(1), pp 122–135.
Advancement of image enhancement in endoscopy - optimising the FICE technique. 1Inglis S, 2Alexandridis S, 2Plevris J N 1Medical Physics, NHS Lothian, UK. 2Centre of Digestive Disorders NHS Lothian, UK. email: [email protected] Background. Endoscopic imaging has significantly advanced over the past 10 years, with the introduction of high resolution CCD and image enhancement technologies (1,2). Flexible endoscopic systems now incorporate enhancement modes such as NBI (Olympus), i-Scan (Pentax) and FICE (Fuji) to aid clinicians in localising pathology(1,3-5). Each mode either alters the wavelength of transmitted light or performs real-time manipulation of the video frames. Fuji Intelligent Chromo Endoscopy (FICE) is one such post-processing technique. It has 10 preset settings but it is also programmable. It works by taking each frame, separating it into discrete wavelengths, and combining 3 selected weighted wavelengths (from 400–700nm) and superimposed onto the white light image to produce the FICE image. The aims of this project are: to evaluate the FICE settings on the EPX4400 processor, and create new settings to improve the application of FICE in the diagnosis of oesophageal pathology. Methods. A PC based FICE simulator, provided by Fuji (Japan), was used to process images offline. Images were captured during diagnostic endoscopies of various conditions (e.g. varices, Barrett’s oesophagus) using the EPX-4400 processor. Using the FICE simulator, new FICE settings were created to maximise enhancement and maintain anatomical colouring. Forty images were selected of various conditions, and were processed via the FICE simulator using the 10 standard and 2 new settings. The images were randomised and evaluated by 5 blinded endoscopists. Each endoscopist compared the original and FICE image and scored the degree of enhancement over the original image from 0 (no enhancement) to 5 (maximum). Results. The oesophageal mucosa presented with 2 distinct shades of pink (e.g. Light and Dark). Two settings were created, one for each mucosal shade (L1 -Light and L2 - Dark). Of the 40 images 65% would be characterised as Light and 35% Dark mucosa. Out of a possible enhancement score of 1000, the standard FICE Settings scored between 202 and 319. The Lothian FICE settings L1 and L2 scored 463 and 387 respectively. An example of oesophageal varices is illustrated in Figure 1 using white light, the best FICE setting (9) and the L1 setting.
Figure 1. Example of varices in the oesophagus under white light, FICE setting 9 and custom FICE setting L1. Discussion & Conclusion. FICE is unique in that it is possible for the settings to be customised. However the 1st generation settings could not adequately delineate pathology and in our study we have shown that improvements could be obtained by altering the FICE settings. The L1/2 FICE settings were found to provide further enhancement compared with current FICE settings by improving discrimination between normal and abnormal mucosa. FICE remains a useful and flexible system with a lot of potential but still requires optimisation. Key references. (3) Chung SJ et al. Gut 2014, 63(5):785-791 (1) Galloro G. World J Gastrointest Endosc. 2012; 4(2): 22–27. (4) Osawa H, Yamamoto H Dig Endosc 2014, 26 Suppl 1:105-115 (2) Subramanian V, Ragunath K Clin Gastroenterol Hepatol 2014, 12(3):368-76 (5) Yoshida et al. World J Gastrointest Endosc 2012 4(12): 545-555
Texture Analysis Toolbox: a comprehensive analysis of molecular images for cancer research 1Jun L, 1James W, 1Mike P 1Department of Oncology, University of Oxford, UK. email: [email protected] Background: Texture is one of the important characteristics used in identifying objects or regions of interest (ROI) in medical images. The spatial arrangement of image intensities, or texture, can be quantified by a set of matrices and their corresponding indices. Investigation of these matrices and indices is of growing interest for image classification and treatment response assessment in CT, MRI and PET. Commonly used matrices include Gray-Level Co-occurrence Matrix(GLCM) and Gray-Level Run Length Matrix(GLRLM), however there are no standard tools to generate these matrices and indices in the public domain. This lack of tools and methodologies can make comparison of published results difficult between centres. The aim of this work is to develop a MATLAB toolbox to generate a standard set of matrices and indices for medical image texture analysis. The application of the toolbox is demonstrated using 18FDG PET and CT images from patients with locally-advanced pancreatic carcinoma treated with chemoradiotherapy. Methods: The framework for texture analysis follows a data mining process comprising medical image data pre-processing, mathematical models, applications, model verification and sensitivity analysis. Based on previously-delineated regions of interests (ROI) on the medical images, the toolbox generates a set of matrices including Gray-Level Co-occurrence Matrix (GLCM), Gray-Level Run Length Matrix (GLRLM), Gray Level Size Zone Matrix (GLSZM), Neighboring Gray-level Dependence Matrix (NGLDM), Neighborhood Gray-tone Difference Matrix (NGTDM), First Order Statistics and more than forty corresponding texture properties, including Energy, Entropy and Contrast. All matrices and texture features are derived from the well-defined literature sources [1-5]. The expected units for the ROI data are HU for CT images and SUV for PET images. Functions in the toolbox are parameterized. Sensitivity analysis is integrated into the toolbox functions and can be applied according to windowing scales, grey levels and ROI segmentation methods. The toolbox is developed in MATLAB based on built-in and open source functions. Results and Discussion: Currently the toolbox produces six matrices and more than forty indices with a potential composition of 240. Our preliminary results indicate that the Texture Analysis Toolbox is a useful tool for medical images analysis. It can quantify images and identify unique features of the images based on the textural matrices and corresponding indices. It can compute and study image properties potentially useful for classification and prediction of pathologic tumour responses to radiotherapy and chemoradiotherapy (CRT). The toolbox can be integrated with EsmeProcess [6] – a contouring and statistical tool to produce ROIs and carry out first order statistical and fractal analysis, forming an integrated textural analysis environment. Future developments will focus on methodologies for classification and prediction of treatment response and extension to fully 3D analysis. Conclusion: The Texture Analysis Toolbox presented provides a comprehensive set of tools for medical image texture analysis, generating a large set of standard matrices and indices. Although the toolbox has been designed primarily for medical image analysis, its application will also be possible in other fields. References 1. R.M. Haralick et. al. (1973), IEEE Trans Systems Man and Cybernetics, SMC-3, No. 6: 610-621 2. D-H. Xu et. al. (2004), The 4th Int. Conf. on Visualization, Imaging, and Image Processing 3. C. Sun et. al. (1983), Computer Vision, Graphics, and Image Processing, 23(3), 341-352 4. G. Thibault. et. al. (2009), Pattern Recognition and Information Processing (PRIP): 140–145 5. M. Anantha et. al. (2004), Comput Med Imaging Graph. 28(5): 225–234 6. J. Li, E. Hill and M Partridge (2013) Dicom Operator-EsmeProcess http://www.mathworks.co.uk/matlabcentral/fileexchange/43397-dicom-operator-esmeprocess
Monday 1st September 2014, 12.10 – 12.55 Woolmer lecture
Medical Physics: A Gateway to Innovation Keating D, NHS Greater Glasgow & Clyde, UK Email: [email protected] The ageing population with increased chronic disease coupled with increased expectation from the general public place an enormous burden on healthcare resources. The focus is shifting from acute care to prevention and detection of disease processes. It is widely recognised that the success of Health and Social Care Integration can only be achieved through innovation. For many years, Medical Physics have had staff embedded in clinical areas. Their role is to ensure safe delivery of efficient clinical services. There are numerous examples where these staff contribute or lead the development or introduction of disruptive technologies to clinical services. In addition, Medical Physics are often the link between clinical service, academia and industrial partners.
In recent years, advances in technology enable diagnostic procedures previously implemented in hospital settings to be transferred into community or home settings. In addition, the computing power and miniaturisation of devices such as tablet or mobile phones enable new diagnostic and screening devices to be utilised earlier which will provide improved screening, detection and treatment of disease. This in turn should reduce the burden of acute admissions relieving the pressure on our acute services.
Medical Physicists and Technologists are in a prime position to embrace Health and Social Care Integration. The skills, experience and collaborations with clinical staff, academia and industry should enable Medical Physics to be the gateway to innovation which will ultimately make the biggest impact in modern healthcare delivery.
Monday 1st September 2014, 13.45 – 15.15 Professional Session II
Service Accreditation – Improving Quality in Clinical Engineering and Physical Science Services - The iCEPSS Project Jarritt P; iCEPSS Project Manager Email: [email protected] The iCEPSS project was commissioned by the Chief Scientific Officer for NHS England in mid 2013 to establish a service accreditation and quality improvement tool for services covered with the Physical Sciences domain of Healthcare Science. The project was designed to build upon the successful IQIPS project that is available for Physiological Services and also recognized the existing CPA accreditation scheme for pathology laboratories.
The Academy for Healthcare Science was commissioned to deliver the project in conjunction with IPEM who have provided the specialist expertise to develop service specific standards. The project was launched in January 2014 to a wide range of stakeholders and many of these remain actively involved in the development of the standard. These include Institute of Health Engineering and Estate Management (IHEEM), the British Nuclear Medicine Society, UK Radiopharmacy Group, RESMAG, Clinical Movement Analysis Society, Maxillo-facial professional group etc.
It is recognized that many of these groups already have professional standards and accreditation programmes and that many departments have already achieved certification to one or more international standards. Significant effort has been taken to ensure that existing professional standards and certification programmes can contribute to the proposed iCEPSS accreditation programme. This paper will provide a brief overview of the developing role of accreditation within the NHS together with details of the iCEPSS programme including its current status and future timetable. The paper will highlight opportunities to contribute to the introduction of the standard through the pilot phases of the project.
The paper will conclude with a brief introduction to the development of a British Standard (BS70000) for service accreditation and the links to the European Federation of Organizations for Medical Physics (EFOMP).
Monday 1st September 2014, 13.45 – 15.15 Magnetic Resonance Imaging in Radiotherapy
Observations and rationale for MR-linac use: the Australian MR-linac project as an example 1,2Thwaites D I, 3Keall P, 4Holloway L, 2,5Sykes J, 5Cosgrove V 1Institute of Medical Physics, School of Physics, University of Sydney, Australia. 2Medical Physics, Leeds Teaching Hospitals and University of Leeds, UK. 3Radiation Physics Lab, Medical Faculty, University of Sydney, Australia. 4Medical Physics, Liverpool Cancer Therapy Centre, Liverpool (Sydney), Australia 5Medical Physics, St James’s Institute of Oncology, Leeds Teaching Hospitals. Leeds, UK. email: [email protected] Background. Image guided radiotherapy (IGRT) at the point of treatment is now widely available in RT centres, based mainly on 2D and 3D x-ray systems, but with ultrasound and other systems also used. MRI can provide excellent soft tissue imaging and the potential for functional imaging and a number of hybrid systems are being developed with MR in the RT treatment room for imaging at the point of treatment. Notable examples are the pioneering MR-linac work at Utrecht and the Viewray system combining MRI with Co-60 radiation sources, now in clinical use. The University of Sydney in partnership with Liverpool Hospital, is developing an MR-linac system to investigate comparative performance of in-line and perpendicular ( to the magnet bore) systems, in a project lead by Paul Keall. The rationale of MR-linac use generally and the potential of the different layouts and systems is reviewed. Methods. The literature on a range of approaches for combining MRI imaging and radiotherapy treatment systems is reviewed, to summarise the different systems, their status, their potential advantages and disadvantages and their intended development. The Australian system (6 MV linac , 1T magnet) is described in more detail along with the comparative rationales and likely advantages and disadvantages of in-line and perpendicular systems. Results. Pros and cons of the different systems are significant, but all provide the advantages of MRI imaging, although with different strength magnets and hence different potential. The likely advantages of the in-line mode in the Australian system include effects on the linac, but the layout requires the patient to be rotated, with potential organ changes to be assessed and compensated for. Electron transport effects between the two modes are mixed. Discussion and Conclusion. MR-linacs have the potential for improved IGRT and functional IGRT, linked to biological targeting and dose painting. Some systems are in clinical use or close to clinical use. Their wider implementation is likely to follow, leading to a new paradigm in IGRT.
Assessment of deformable image registration (DIR) between planning CT and diagnostic MRI for H&N patients on an individual patient basis: Is qualitative clinical assessment acceptable or is quantitative assessment required? 1Speight R, 1Perkinson A, 1Smith D, 2Prestwich R, 2Sen M, 2Ramasamy S, 1Wright S, 1,3Sykes J 1 Department of Medical Physics and Engineering, Leeds Teaching Hospitals NHS Trust, Leeds, UK 2 Department of Clincial Oncology, Leeds Teaching Hospitals NHS Trust, Leeds, UK 3 Institute of Medical Physics, University of Sydney, Crown Princess Mary Cancer Centre, and Nepean Cancer Care Centre, Sydney, Australia email: [email protected] Background. In radiotherapy treatment planning deformable image registration (DIR) allows diagnostic MRI to be registered to the planning CT which can increase volume delineation accuracy. Quantitative assessment of DIR quality is time consuming and should be done during commissioning to assess weaknesses of algorithms. The aim of this study is to determine if a quicker qualitative clinician assessment is an appropriate surrogate for quantitative assessment on an individual patient basis. Methods. DIR between planning CT and diagnostic MRI was performed for 5 patients using Mirada RTx (v1.2, Mirada Medical, Oxford, UK). Qualitative clinical assessment of DIR quality was performed by 3 radiation oncologists at 7 points (centre of cord (at C2, C4 and C6), left and right orbits, floor of mouth (FOM) and posterior of larynx). Registrations were assessed as 1 (highly confident), 2 (confident), 3 (questionable) or 4 (not useable), pass criteria ≤2. DIR quality was quantitatively assessed by measuring distance to agreement (DTA) for the first 5 points and mean DTA between 3cm diameter spheres propagated around a closed registration loop starting and ending with CT for the last 2 points, pass criteria ≤5mm. Fast DIR clinical assessment results were compared to the slower quantitative assessment results to observe their equivalence. Results. Quantitative assessment determined DIR a failure for 5/35 points (all in the spine), clinical assessment by all 3 clinicians agreed DIR failed for 4/5 of these. Of the points passing quantitative assessment (30/35) clinical assessment by all 3 clinicians agreed points passed for 83% of points, leaving 10% where 1 or 2 clinicians agreed and 7% where clinical assessment disagreed with quantitative results (all in the spine). Inter-observer reproducibility of clinical assessment was high with all clinicians agreeing registrations either passed/failed for 91% of points (all disagreements in the spine). Results from 2 patients are shown in figure 1. DTA and Clinician assessment for patient 3 out of shell DTA and Clinician assessment for patient 5 out of shell
13 4 13 4 DTA (mm) DTA (mm) 12 12 11 Observer 1 11 Observer 1 10 Observer 2 10 Observer 2 9 Observer 3 3 9 Observer 3 3 8 8 7 7 6 6 5 5 4 2 4 2
3 3 Clinical assessement Clinical
2 2 assessement Clinical DTA or meanDTADTA (mm) or 1 DTA mean or DTA(mm) 1 0 1 0 1 C2 C4 C6 L orbit R orbit FOM Post C2 C4 C6 L orbit R orbit FOM Post larynx larynx
Figure 1. Graphs to show the DTA (left axis) and clinical assessment (right axis). Results are for the best case (patient 3, left) and worst case (patient 5, right).
Conclusion. Volume delineation in radiotherapy treatment planning can be improved by accurate DIR between planning CT and diagnostic MRI. Quantitative assessment of DIR quality should be performed during commissioning of DIR algorithms to understand their weaknesses, however this is time consuming and unsuitable for individual patients. The current work demonstrates faster qualitative clinical assessment of DIR quality has both a good correlation with quantitative assessment and has a high degree of inter- observer reproducibility (>90%). Therefore it is recommended that after quantitative commissioning clinician assessment is appropriate to evaluate DIR for individual patients. Special care should be taken for regions around the spine.
Target Registration Error of Diffeomorphic Image Registration of Same Breath-Hold 1H and Hyperpolarized 3He MRI to Lung CT for radiotherapy treatment planning 1Tahir BA, 2Swift AJ, 2Marshall H, 2Leung G, 2Parra-Robles J, 1Hatton MQ, 3Hartley R, 4Kay R, 3Brightling CE, 2Wild JM and 1,2Ireland RH 1Academic Units of Clinical Oncology and 2Academic Radiology, University of Sheffield, UK. 3Institute for Lung Health, University of Leicester, UK. 4Novartis, Basel, Switzerland. Email: [email protected] Background. Analysis of hyperpolarized 3He-MRI fused with CT has a number of important potential applications, including functionally-weighted radiotherapy treatment planning in lung cancer [1], that require accurate and reproducible image registration of ventilation MRI to CT. However, there are two main difficulties with automatic 3He-MR image registration. Firstly, registration of functional 3He-MRI with anatomical images requires sufficient ventilation within the MR image to enable multimodal registration to succeed. Secondly, the presence of ventilation defects also makes the quantification of registration error problematic [2]. To evaluate registration accuracy, a recent MICCAI grand challenge on pulmonary deformable registration proposed that target registration error (TRE) of corresponding expert defined anatomical landmarks was the best validation method for distinguishing between registration algorithms [3]. Hence, a method of 3He-MRI to CT registration that enables TRE analysis would be desirable. This study presents a method for image registration of hyperpolarized 3He-MRI and CT using 1H-MRI synchronously acquired in the same breath-hold as 3He-MRI. Direct (3He-MRI to CT registration) and indirect (3He-MRI to CT registration using 1H-MRI) methods were compared for 15 patients using a diffeomorphic transformation. Methods. Image registration was performed using the antsRegistration tool incorporated as part of the Advanced Normalization Tools (ANTs) [4]. For each patient, the 3He-MRI and 1H-MRI (moving images) were registered to CT (fixed image) using an initial rigid pre-alignment followed by affine and diffeomorphic transforms. The registration accuracy was evaluated by the target registration error (TRE) of corresponding anatomical landmarks identified on the anatomical 1H-MRI and CT. Results. TRE for direct and indirect methods was 20.4±12.8mm and 13.5±3.3mm, respectively (Wilcoxon signed-rank test: p=0.006).
Figure. Corresponding coronal slices for a representative patient showing warped 3He- MRI fused with CT via the direct (bottom left) and indirect (bottom right) methods with preregistered 3He-MRI (top left) and 1H-MRI fused with 3He-MRI (top right). The blue arrow near the base of the left lung indicates a registration error in the direct method when compared to the corresponding slice of the unregistered 3He-MRI. Discussion & Conclusion. This study demonstrates the improved accuracy of indirect image registration of 3He-MRI to CT via same breath-hold 1H-MRI. Potential clinical applications of this improved method of 3He- MRI to CT fusion include functionally-weighted radiation treatment planning and quantification of lobar ventilation in obstructive airways disease. Key references. 1. Ireland, R.H., et al., Feasibility of image registration and intensity-modulated radiotherapy planning with hyperpolarized helium-3 magnetic resonance imaging for non-small-cell lung cancer. Int J Radiat Oncol Biol Phys 2007, 68(1):273-281. 2. Ireland, R.H., et al., An image acquisition and registration strategy for the fusion of hyperpolarized helium- 3 MRI and x-ray CT images of the lung. Phys Med Biol 2008, 53:6055-6063. 3. Murphy, K., et al., Evaluation of registration methods on thoracic CT: the EMPIRE10 challenge. IEEE Trans Med Imaging 2011, 30(11):1901-20. 4. Avants, B.B., et al., A reproducible evaluation of ANTs similarity metric performance in brain image registration. Neuroimage 2011, 54(3):2033-44.
Is commercial deformable image registration (DIR) software adequate for CT – MRI registration in breast radiotherapy patients? 1Speight R, 1,2,3,4Sykes JR, 3Stensmyr R, 4Foo J, 5,6Pogson E, 5,6,7Liney G, 5,6,7,8Holloway L, 8Thwaites DI 1 Department of Medical Physics and Engineering, Leeds Teaching Hospitals Trust, Leeds, UK 2 Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW, Australia 3 Crown Princess Mary Cancer Centre, Westmead, Sydney, NSW, Australia 4 Nepean Cancer Care Centre, Nepean Hospital, Kingswood, NSW, Australia 5 Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia 6 Liverpool and Macarthur Cancer Therapy Centres and Ingham Institute, NSW, Australia 7 University of New South Wales, Sydney, NSW, Australia 8 Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW, Australia email: [email protected] Background. Radiotherapy plays an important role in breast cancer therapy with treatments typically planned on a supine-CT image. Deformable image registration (DIR) allows MRI to be registered to CT which can improve accuracy of tissue definition. MRI is normally acquired with the patient prone utilising dedicated coils for improved image quality, this increases deformation between the two scans and hence makes DIR more complex. The aim of the current study was to assess if commercial DIR software can accurately register supine-CT to prone-MRI images to allow MRI to be utilised in treatment planning. Methods. The Mirada RTx-1.2; Velocity AI-3.0.1; and MIMs-6.1.6 commercial DIR software packages were used to register 10 patients who had CT and T1 or T2 weighted MRI acquired both supine and prone. To assess the limitations of the algorithms DIR was performed between images with a change in 1) imaging- modality, 2) patient orientation and 3) both. Results. Results for all DIR software tested were similar. DIR between imaging modalities with a fixed orientation of either prone or supine lead to clinically adequate accuracy (<5mm) for 6 out of 10 patients (figure 1a). DIR was more successful using T1 MRI. DIR between different patient orientations with a fixed imaging modality were poor (>10mm) for all systems. Algorithms attempted to register the external at the expense of breast tissue detail. Accuracy was unacceptable for DIR between supine-CT and prone-MR. Figure 1b shows an example with the nipple registered incorrectly and unrealistic deformations within the lung. a b
Figure 1a: successful DIR between prone-CT and prone-T1 MRI. Figure 1b: unsuccessful DIR between supine-CT and prone-T1 MRI Conclusion. The current work found that commercial DIR software is acceptable for registering CT-MRI in the same geometry with accuracy increasing with T1 MRI. Registering CT-CT, MRI-MRI or CT-MRI between prone and supine position is beyond the capabilities of the DIR software. For such registrations there is a need for intelligent algorithms including prior knowledge. Key references. 1. Australian and New Zealand Clinical Trials Registry [Internet]: Sydney (NSW): National Health and Medical Research Council (Australia); 2013 - Identifier ACTRN12613000253707. TROG 12.02 PET Scans for Locally Advanced Breast Cancer and Diagnostic MRI toDetermine the Extent of Operation and Radiotherapy; 2013 March 4 [cited 2014 March 19]; [10 pages]. Available from https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=363490.
Monday 1st September 2014, 13.45 – 15.15 Trainee Session III
Evaluation on the performance of QUICKCHECK in clinical use 1Choi O-C, 1Harold D’Souza, 1Medical Physics, Cancer Centre London, UK. email: [email protected] Background. QUICKCHECK has been implemented in Cancer Centre London since Oct 2012 for daily morning check. We aimed at evaluating the performance of QUICKCHECK. Methods. Daily measurement data were collected for Siemens Primus linear accelerator with PTW QUICKCHECK measurement device. Firstly the readings on two different QUICKCHECK on the same machine were compared. Then, two day measurements per month were randomly selected and being analyzed. The Central Axis Data (CAX) then compared with our monthly dosimetry QA with ionization chambers. Results. The readings between two different PTW QUICKCHECK were within 0.5% for the same measurement. The Central Axis reading for 6MV and 10MV were within ±1.0% difference while the chamber reading had similar trends of result within ±0.6% difference. The wedged beam had out of tolerance result 1 or 2 times per month and it was justified by the farmer chamber measurement, otherwise, QuickCheck had not picked up any major errors in the department. The tolerance in the QuickCheck measurement is ±3.0% in the department.
The percentage difference between PTW-QC-P1 and PTW-QC-P2 readings CAX Flat/Wedge SYM GT SYM LR BQF
6MV CAX measurement 1 2 measurem 3 ent reading 4 5 6
Discussion. The QUICKCHECK gave a generally stable measurement. Out of tolerance data were mostly come from a wrong machine input or in a wedged beam. After checking with farmer chambers measurement for a consistent result, the tolerance of wedged beam measurement increased to ±5% from ±3%. Conclusion. The QUICKCHECK had a quite stable performance for both photon and electron measurements compared to farmer chamber or NACP chamber reading. It offers a quick and easy way to check the machine performance. Key references. 1. PTW QUICKCHECK user guides.
Evaluation of measured dose in IMRT treatment delivery using diode invivo dosimetry system 1Choi O-C, 1Harold D’Souza, 1Henry Weatherburn 1Physics Department, Cancer Centre London Parkside Hospital, UK. email: [email protected] Background. With the increasing number of IMRT patients, it is increasingly important to undertake an in vivo dosimetry routinely at minimal cost in radiotherapy departments. The purpose of this work is to evaluate the routine use of diodes for IMRT treatment in vivo dosimetry within our department. Methods. 14 pelvis patients undergoing IMRT ‘step & shoot’ treatment in 2012 and 2013 who had 32 dose measurements with Scanditronix PDP diodes were selected in this study. The diode positions were at field centres which is the most readily identifiable point in the treatment field: beams passing through the couch are not considered. The dose at each measurement point was calculated at Dmax from the TPS and corrected for SSD to the surface. The radiographers in the treatment machine performed the dose measurement with the diode set up position. The tolerance level is 5% at each field, 5-8% was the observation limit and 10% was the action levels. Results. 1 out of 32 (3.1%) beams had a measured difference of greater than 10%, 5 out of 32 (15.6%) having reading between 5-10% difference, and 26 out of 32 (81.3%) had dose measurement within 5%, median 1.67%, standard deviation 4.1. 3 out of 32 measurements had been repeated due to greater than 10% discrepancy being observe but were then within tolerance, the differences were due to mis-positioning. Discussion. The use of diode for IMRT pelvis treatment in vivo dosimetry had 81% with IMRT field measurements within ±5%, which can give estimation on the dose received by the patient during treatment. The diode positioning is very important and a repeat measurement is required if an unsatisfactory result is initially found, and investigation is required for a persistent unsatisfactory result. Conclusion. Within the limitations of hospital resources, diodes are a quick and efficient way to check the dose given to the pelvis patients clinically. Diodes can be considered as an invivo verification test for pelvis patients in addition to pre-treatment patient specific QA, where plan verification QA is the most preferred and accurate tools to verify and assure the plan is correctly delivered with tighter constraint in dose and distance validation. We plan to undertake a TLD/EPID dosimetry later this year for comparison. Key references. 1. Vinall A, Williams A, Currie V, Van Esch A, Huysken D. (2010). Practical guidelines for routine intensity-modulated radiotherapy verification: pre-treatment verification with portal dosimetry and treatment verification with in vivo dosimetry. The British Journal of Radiology 83, 949-957
the percentage differnce of measured and calculated error in vivo dosimetry with diode
% difference
treatment beams
DaTSCAN quantification: comparison of DaTQUANT, BRASS and the Southampton method. 1Riddick J, 2Gannon M, 3Cullum I, 4Dickson J 1Nuclear Medicine Department, Lincoln County Hospital. 2Department of Medical Physics, Sunderland Royal Hospital. 3Department of Nuclear Medicine, Addenbrookes Hospital, Cambridge. 4Institute of Nuclear Medicine, University College Hospital, London. email: [email protected] Background. Nuclear Medicine dopamine transporter (DAT) imaging has long been a useful tool in the investigation of patients with suspected neurodegenerative parkinsonism. Recent guidance from the European Society of Nuclear Medicine and the Society of Nuclear Medicine recommends that semi- quantitative analysis is performed alongside visual interpretation during reporting to yield more objective results. It is most convenient to calculate specific binding ratios (SBRs), which compare the specific uptake in a structure of interest to the non-specific uptake in a reference region that does not contain DATs. DaTQUANT (GE healthcare) and BRASS (Hermes Medical Solutions) are two commercially available, fully automated pieces of software, which register images to a 3D reference normal template and apply anatomical VOIs to structures of interest using a VOI atlas. The normal template in both programmes is created from a set of subjects from the ENC-DAT database [1]. An alternative semi-automated method has been developed by a group in Southampton [2], which applies geometrical regions of interest (ROIs) to the striata and so includes partial volume counts in the SBR. The aim of the current study is to compare DaTQUANT, BRASS and the Southampton method in terms of values obtained and ease of implementation and use. Methods. The three quantification methods described above were applied retrospectively to the images from a cohort of 83 patients who were referred for a DaTSCAN within the Department of Nuclear Medicine at Addenbrookes hospital between May 2013 and February 2014. The distribution of results was 22 normal, 48 abnormal and 13 equivocal scans. A ‘normal’ range consisting of the mean ± 1.96 standard deviations was established from the striatal (All), putaminal and caudate (BRASS and DaTQUANT) SBRs from the 22 normal scans. This normal range was then applied to the abnormal and equivocal scans to determine the result based on semi-quantitative analysis alone. This was then checked for diagnostic concordance with the report issued by experienced clinicians from visual analysis. Results. The normal ranges calculated for the normal patient cohort for the striatal SBRs were 1.96 ± 0.92, 1.94 ± 0.86 and 8.17 ± 3.46 for DaTQUANT, BRASS and the Southampton method respectively. Diagnostic concordance was 84.4 % (DatQUANT), 80.0% (BRASS) and 65.8 % (Southampton). For DatQUANT and BRASS when the SBRs from putaminal VOIs were used instead, diagnostic concordance improved to 93.2 % and 88.6% respectively. Discussion/Conclusion. Out of the 83 DaTSCANs processed, the VOIs generated by DaTQUANT were in general a good fit to the data. Although manual adjustment was not available in the trial version used in this study, this was not necessary, and this functionality is available in the full version. The VOIs generated by BRASS were not adequate in approximately 10% of cases and so had to be repositioned manually. This could account for the differences in diagnostic concordance between the two methods. Writing the Aladdin programme to perform quantification by the Southampton method required a significant time commitment however once this was in place it was easy to use and would provide a useful alternative to the commercial software. References 1) Varrone et al ‘European multicentre database of healthy controls for [123I] FP-CIT SPECT (ENC- DAT):age-related effects, gender differences and evaluation of different methods of analysis’ Eur J Nuc Med 40 (2013) pg 214. 2)Tossici-Bolt et al ‘Quantification of [123I] FP-CIT SPECT brain images: an accurate technique for measurement of the specific binding ratio’ Eur J Nuc Med 33 (2006) pg 1491.
A Novel Subtraction Method for Indium-Marrow Imaging of Infected Joint Prostheses 1Turner C, 1,2HJ Wallace, 1,2AA Bolster. 1University of Glasgow. 2Department of Nuclear Medicine, Glasgow Royal Infirmary (GRI). email: [email protected] Background. A common complaint from patients following prosthesis surgery is further pain from the joint and surrounding area. The differential diagnosis of this pain includes aseptic loosening and infection around the prosthesis. Nuclear medicine plays a significant role in the diagnosis of joint infection; patients initially have a Tc99m labelled MDP three phase bone scan, this would exclude infection if negative. Following a positive result, the patients undergo another scan which is more specific for infection. This is a dual-isotope scan which uses two radiopharmaceuticals of different energies (In111 and Tc99m) to produce two registered images of the bone marrow (Tc99m Nanocoll) and In111 labelled white blood cell distribution around the joint. The marrow part of the investigation allows pockets of compacted marrow to be identified. Areas which have white cell accumulation in the absence of marrow are diagnostic of infection. However, the sensitivity and specificity of this study are compromised due to the poor image quality of the In111 scan. This is primarily because of the low activity which can be administered. The aim of this project was to investigate whether a subtraction method could be used to improve the observer’s confidence in their findings. Methods. A subtraction of background count was undertaken to remove scatter from the image. A ratio of counts between the Tc99m and In111 images was calculated, by drawing regions around areas of healthy bone. The indium image was scaled using this ratio. Finally the technetium image was subtracted from the scaled indium image to create a subtraction image. The analysis of this novel method was carried out using groups of known negative and known positive patients, with the total number of images observed, N=132. The images were randomised prior to being presented to experienced observers. The images sets were, either, the original two images of the indium and technetium, or, contained these originals plus the newly created subtracted images. The observers were asked to rank their finding as definitely negative, marginally negative, marginally positive or definitely positive. Results. Introduction of subtracted images showed no change in reported outcome in the vast majority of cases (119/132 and 123/132 for observers 1 and 2 Observer Confidence Following Subtraction respectively). A Wilcoxon Matched Pairs test showed no statistically significant bias towards positive or negative 30 change (p1=0.4054, p2=0.3873). However, the 25 introduction of subtracted images resulted in a higher proportion of cases with increased confidence for both 20 observers, as shown in Figure 1. A Wilcoxon Matched Observer1 Pairs test showed this to be a statistically significant 15 Observer2 difference (p1=0.0004, p2=0.0031).
10 Discussion. The results show there is a clear increase in Number Number of Cases the confidence of the observer’s decision. There was no 5 Gold Standard available for this retrospective study and so it was not possible to assess sensitivity and specificity 0 Increased Decreased for this novel method. Change in Confidence Conclusion. These results suggest that this new method Figure 1: Change in observer’s confidence following of subtraction does provide the observer with useful viewing of subtracted images information, meaning that they are able to give more confident decisions for the diagnosis of these patients. Future work will include a larger pool of experienced observers to determine whether this method could be installed into routine clinical practice.
Can the Edinburgh Pipe Phantom be used to detect failed elements on phased array ultrasound transducers? Welsh D, Inglis S, Pye S D Medical Physics, NHS Lothian, Royal Infirmary, Edinburgh EH16 4SA, UK email: [email protected] Background. Imaging faults with ultrasound transducers are common [1], with the need for transducer QA established. Failed elements can sometimes be detected with a simple image uniformity or “paperclip” test as recommended by IPEM Report 102 [2] on conventional array transducers. However, this method is much less effective for phased array transducers. An alternative is to use an automated probe testing system, such as the Sonora FirstCall [3, 4]. Automated systems can accurately identify failed elements, but they are expensive and require transducer-specific adaptors and data files, which may not always be available. The aim of this project was to assess whether failed elements could be detected through measurement of the resolution integral using the Edinburgh Pipe Phantom [5, 6], as a simple and low cost alternative to automatic probe testing systems. Methods. Failed elements were simulated using layered polymer tape as an attenuator. This approach was validated using a linear array transducer. The tape was then cut to size and affixed to the centre of a 128 element phased array transducer face (P10-4, Siemens, Germany). Measurements of resolution integral (R), including low contrast penetration (LCP), were made with the probe uncovered to act as a baseline, and repeated for several widths of tape (0.5 to 5 mm) to simulate varying numbers of failed elements (0.1 mm equates to approx 1 element). The results were compared with the baseline values. Results.
All widths of tape resulted in a significant difference from baseline, with the exception of 0.5 mm. The measurement of LCP also showed a similar pattern, albeit with smaller differences. Discussion. The results show that the measurement of R and LCP are sensitive to the presence of failed elements for phased array transducers. Particularly encouraging is the result for LCP as this is an easy measurement to make and can be done with many different test objects, thus enabling “in the field” checks. This would require baseline values to be established at commissioning. The measurement of R could also be used to determine whether a known defect results in significant drop in image quality. It is recommended that further work be carried out to assess the sensitivity of the test for truly failed elements and other models of phased array transducer. Conclusion. We have shown that the measurement of resolution integral and low contrast penetration both have the potential to be used as quick and inexpensive tests to detect failed elements on phased array transducers. Key references. [2] IPEM Report 102. Institute of Physics and Engineering in Medicine; York, 2010 [3] Johansson J-O et al. World Congress on Medical Physics and Biomedical Engineering, 2009, Munich, Germany, Springer; p.145–8 [5] MacGillivray TJ, Ellis W, Pye SD. Phys Med Biol. 2010; 55: 5067–88 [1] Mårtensson M et al. Eur J Echocardiogr. 2009; 10: 389–94 [6] Moran CM, Inglis S, Pye SD. Ultrasound. 2014; 22: 37-43 [4] Sipilä O et al. Eur J Radiol. 2011; 80: 519–25
Video-mosaicing of confocal microscopy images for rapid, non-invasive examination of skin cancer lesions 1Kose K, 1Cordova M, 2Duffy M, 1Flores E, 3Brooks D, 1Rajadhyaksha M 1Dermatology Service, Memorial Sloan Kettering Cancer Center, New York, NY, USA 2King's College Hospital NHS Foundation Trust, London, UK 3Department of Electrical and Computer Engineering, Northeastern University, Boston, MA, USA Email: [email protected]
Background: Reflectance confocal microscopy (RCM) can be used to image the skin in vivo and ex vivo with cellular-level resolution that is comparable to histology. Melanoma and basal cell carcinoma can be noninvasively diagnosed with high sensitivity and specificity, and margins detected to guide surgical excision. However, the field of view (FOV) of an RCM image is limited relative to the typically large areas of lesions to be examined. Through mosaicing- i.e. stitching of a sequence of images –large areas can be displayed for examination. Rapid mosaicing techniques, based on stitching of a pre-determined sequence of still images, have been developed for RCM. Another rapid acquisition technique, called "video-mosaicing," is based on stitching of a video sequence of images and may be more suitable for clinical examination of skin in vivo.
Objectives: To demonstrate the feasibility and clinical potential of rapid video-mosaicing in order to display large FOVs of skin in vivo, by stitching the individual frames (images) from an RCM video.
Methods: RCM videos of skin in vivo were collected with a handheld microscope, with significant overlap between consecutive frames. The frames were extracted from the video, cropped and processed with software (MATLAB and Microsoft Image Composite Editor), and stitched into a mosaic to display large fields of view over the lesion areas.
Results: More than 10 RCM videos of skin in vivo were processed and evaluated to be of high quality. Mosaics obtained from 3 cases (normal skin with benign melanocytic nevi, epidermal margin on a patient during Mohs surgery for basal cell carcinoma, and lentigo maligna) are presented.
Conclusion: The new video-mosaicing method makes it possible for the clinician to rapidly examine large areas of skin in vivo with real-time flexibility in the choice of the imaged area, and without loss of context from surrounding skin as happens with small FOVs. This method may improve the speed, efficiency and accuracy of non-invasive diagnosis and margin detection in patients with skin cancer. Eventually, it may facilitate wider adoption of RCM imaging in the dermatology clinic.
Monday 1st September 2014, 13.45 – 15.15 Innovation in Physiological Measurement Services
Photoplethysmography and its application to clinical physiological measurement – a masterclass 1,2Allen J 1Microvascular Diagnostics, Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK. 2Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, UK. email: [email protected] Photoplethysmography (PPG) is a simple and low-cost optical technique that can detect blood volume changes in the microvascular bed1. The PPG waveform comprises a pulsatile (‘AC’) physiological waveform attributed to cardiac synchronous changes in the blood volume with each heart beat, and is superimposed on a slowly varying (‘DC’) baseline with various lower frequency components attributed to respiration, sympathetic nervous system activity and thermoregulation. PPG technology can provide valuable information about the cardiovascular system, and is used in a wide range of commercially available medical devices for measuring oxygen saturation, blood pressure and cardiac output, assessing autonomic function and detecting peripheral vascular diseases. There has also been a resurgence of interest in the technique in recent years, driven by the demand for low-cost and portable technology for the primary care and community based clinical settings, the wide availability of low-cost and small semiconductor components, and the advancement of computer-based pulse wave analysis techniques. Recent developments of the base technology also include imaging photoplethysmography (iPPG) for non-contact cardiovascular assessment2 and enhanced optical sensor design3.
This physiological measurement masterclass describes the basic principle of operation and interaction of light with tissue, early and recent history of PPG, instrumentation, measurement protocols, and pulse wave analysis. An overview of PPG applications will also be given and include examples from the team’s published studies on peripheral vascular4-6, autonomic function7,8, and endothelial function assessments9.
Key references. 1. Allen J. Topical Review: Photoplethysmography and its application in clinical physiological measurement. Physiol Meas 2007 28:R1-39 2. Allen J and Howell K. Topical Review: Microvascular imaging: techniques and opportunities for clinical physiological measurements. Physiol Meas 2014 35:R91-141 3. Budidha K and Kyriacou PA. The human ear canal: investigation of its suitability for monitoring photoplethysmographs and arterial oxygen saturation. Physiol Meas 2014 35:118-28 4. Allen J, Murray A. Age-related changes in peripheral pulse timing characteristics at the ears, fingers and toes. J Human Hypertension 2002 16:711-7 5. Allen J, Oates CP, Lees TA, Murray A. Photoplethysmography detection of lower limb peripheral occlusive arterial disease: a comparison of pulse timing, amplitude and shape characteristics. Physiol Meas 2005 26:811-21 6. Allen J, Overbeck K, Nath A F, Murray A, Stansby G. A prospective comparison of bilateral photoplethysmography versus the ankle-brachial pressure index for detecting and quantifying lower limb peripheral arterial disease. J Vasc Surg 2008 47:794-802 7. Allen J, Murray A, Di Maria C, Newton JL. Chronic fatigue syndrome and impaired peripheral pulse characteristics on orthostasis - a new potential diagnostic biomarker. Physiol Meas 2012 33:231-41 8. Allen J, Di Maria C, Mizeva I, Podtaev S. Finger microvascular responses to deep inspiratory gasp using wavelet analysis. Physiol Meas 2013 34:769-79 9. McKay N, Griffiths B, Di Maria C, Hedley S, Murray A, Allen J, Novel photoplethysmography cardiovascular assessments in patients with Raynaud’s phenomenon and systemic sclerosis: a pilot study. Rheumatology 2014 May 21. pii: keu196. [Epub ahead of print]
Improvements to the diagnostic value of intracranial pressure recordings 1Marsden S P, 1Boddy I, 2Strachan RD, 1Melia GCR, 1Chambers IR 1Medical Physics Department, The James Cook University Hospital, Middlesbrough, UK. 2Neurosurgical Department, The James Cook University Hospital, Middlesbrough, UK. email: [email protected] Background. Diagnostic intracranial pressure (ICP) monitoring has a low complication rate and can provide valuable information on shunt management for those with idiopathic hydrocephalus syndrome and related conditions [1, 2]. The Medical Physics Department provides an ICP Monitoring Service to the Neurosurgical Department at the James Cook University Hospital. Since its inception in 2006, 109 patients have undergone 182 recordings, usually lasting two nights. Methods. Continuous ICP waveform data are measured using an intraparenchymal Codman transducer connected to an ICP Express box and Powerlab data acquisition system interface with ADInstruments’ LabChart6 software on a laptop PC. Recent additions to the service include a tilt sensor to measure the patient’s posture, a handset to allow patients to input their symptoms, and custom-built software to process, analyse and integrate the data from each device. Results. A number of improvements to the service have been implemented: pressure events can be linked directly to posture changes to better identify pressure drops due to shunt activity, the patient sitting, or other physiological or pathological mechanisms. Relationships between patient symptoms and pressure events can be identified, so that links between headaches, nausea or visual disturbance and pressure can be seen. Artefacts have been rejected from the trace, improving the quality of waveform statistics such as B-wave content [3] and the prevalence of plateau waves. A concise summary clinical report is now generated, which shows more at-a-glance information than previously. This is kept with the patient notes and can inform future decisions. Marking and note-taking tools integrated into the software allow better recording of the diagnostic decision-making process. In addition, amendments to the patient databasing software pave the way for future audits and investigations to expand the evidence base further for the ICP Monitoring Service. Mechanical modifications to the ICP Monitoring Service equipment have made it more robust by preventing accidental improper use of the laptop and giving better infection prevention and control barriers. Discussion. These recent improvements to the ICP Monitoring Service have been enthusiastically accepted and adopted by the neurosurgical team. The patient symptoms handset in particular is proving an invaluable addition, and it is hypothesised that once a sufficient number of patients have been monitored there will be evidence to demonstrate a service improvement. Conclusion. Here we outline a number of improvements to the ICP Monitoring Service at the James Cook University Hospital. We anticipate that the additional information gained through these modifications will lead to better quality diagnostic information, resulting in improved patient care. Key references.
[1] Czosnyka M and Pickard JD. J Neurol Neurosurg Psychiatry 75(6):813-821, 2004 [2] Eide PK and Sortberg W. Neurosurgery 66(10):80-91, 2010 [3] Eklund A et al. J Neurosurg 94:392-396, 1994
Feasibility study: Ambulatory skin temperature asymmetry measurement in complex regional pain syndrome over 24 hours using iButtons® 1 Hart D, 1 Shipley J, 2 Lewis J, 2,3 McCabe C 1 Clinical Measurement Department, Royal National Hospital for Rheumatic Diseases, Bath, UK. 2 Bath Centre for Pain Services, Royal National Hospital for Rheumatic Diseases, Bath, UK. 3 The Faculty of Health and Life Sciences, University of the West of England, Bristol, UK. Email: [email protected] Background: Complex Regional Pain Syndrome (CRPS) is a relatively rare condition where pain in a limb becomes a major disabling factor. It most commonly affects one limb and is characterised by prolonged or excessive pain and changes in skin colour, temperature, and/or swelling associated with superficial blood flow. Currently, Infra-Red Thermal Imaging (IRTI) is used to assess limb surface temperature of patients with the condition. IRTI enables visual representation and identification of temperature asymmetries considered significant, |Right - Left| ≥2.0˚C, but it is limited to a one-off measurement under static conditions in an outpatient hospital environment. This research assesses the feasibility of using ThermoChron iButton® temperature loggers (Figure 2) to measure spot temperature asymmetries over 24 hours within a home based environment. Methods: A case study series of 6 unimpaired participants and 6 patients attending a CRPS therapy programme and who have previously demonstrated a limb temperature asymmetry of ≥2.0˚C during IRTI is underway. iButtons® are worn as close as can be tolerated to the area of pain and in the same position on the contralateral limb. A third iButton® is worn above clothing in order to measure ambient temperature. Synchronised temperature measurements (±1.0˚C accuracy, 0.125˚C resolution) are made every 60 seconds and downloaded to a computer following 24 hours use. These measurements are also compared to those gained by IRTI the previous day. Results: Initial unimpaired participant data indicates an approximately Gaussian frequency distribution of temperature asymmetry measurements centred about 0˚C (Figure 3a). Such plots of patient participants with CRPS data indicates mean temperature asymmetries and frequency distributions characterised by multiple or broadened peeks (Figure 3b). Some participants appear to exhibit different temperature differential frequency distributions when sleeping and awake.
a b
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0.0 1.0 2.0 3.0 4.0
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Right - Left Temp. Diff (DegC) Right - Left Temp. Diff (DegC) Figure 2: Maxim Integrated Figure 3: Examples of right – left temperature differential DS1921H frequency plots ThermoChron a unimpaired participant forearms Mean = 0.13˚C, St.Dev. = 0.77 ˚C iButton® Compeed® cushioned plaster used for attachment to skin. 5 b impaired participant forearms Mean = 1.06˚C, St.Dev.= 1.09 ˚C pence shown for scale.
Discussion: Initial unimpaired participant data has demonstrated monitoring of temperature asymmetry magnitude and frequency within a home based environment. Use of these low-cost, durable temperature sensors appears to enable investigation of previously unreported ambulatory temperature asymmetries in patients with CRPS over 24 hours. Superficial blood flow assessment using iButtons® may also have clinical benefit in connective tissue disease diagnosis/monitoring. Conclusion: The use of commercially available ThermoChron iButtons® may provide useful clinical information that improves understanding of vascular changes associated with CRPS. Ambulatory temperature measurement has utility to other clinical applications and therefore iButtons® may be of use as part of other low cost home based monitoring systems.
Electrophysiological effects of Gifinitib (Iressa) and Irradiation on head and neck cancer cells using Dielectrophoresis (DEP) Mahabadi S, Fatima H. Labeed and Michael P. Hughes Department of Biomedical Engineering, University of Surrey, Guildford, UK email: [email protected]
Background. The application of Dielectrophoresis (DEP) in cancer research can be defined by its exceptional potential to determine the electrophysiological properties of the cells through applying a non- uniform electric field to the cells. The electrophysiological properties include conductivity and permittivity of the membrane and cytoplasm (1,2,4). Gifinitib (Iressa) or ZD1839 is one of the most commonly used drugs for treatment of cancer such as breast and head and neck. This drug damages the local tumours through blocking the activity of EGFR (epidermal growth factor receptor) which are identified as key driver of tumour growth in cancer. Use of EGFR inhibitors like Gifinitib combined with irradiation can decrease the un-controlled proliferation of tumour cells expressing EGF Receptors (3). Methods. In this study, the effect of Gifinitib (Iressa) treatment, irradiation and combination of both treatments were investigated through analysis of the electrophysiological properties of the HN5 (Head and Neck Carcinoma) cells by 3-D electrode microwell kit developed at the University of Surrey. Results. The results indicated that cell membrane capacitance of HN5 cells became substantially lower (80%) when the drug treatment was combined with irradiation. In a contrast, cells have shown a slight decrease in membrane capacitance (by 6%) when cells received a single treatment drug treatment. Conclusion. Our study shows that the combination of drug treatment and irradiation produced a marked effect on the membrane capacitance of head and neck cancer cells. This demonstrates that DEP is a useful technique for assessing the electrophysiological properties of cells ( such as cancer) before and after drug and Irradiation treatments. Key references. 1.Cytoplasm Resistivity of Mammalian Atrial Myocardium Determined by Dielectrophoresis and Impedance Methods", 2012, Biophysical journal, vol. 103, no. 11, pp. 2287. 2.Griffiths, D.J. 1998, Introduction to Electrodynamics, 3rd ed edn, Prentice Hall. 3.Herbst, R.S. 2004, "Review of epidermal growth factor receptor biology", International Journal of Radiation Oncology* Biology* Physics, vol. 59, no. 2, pp. S21-S26. 4.Huang, Y., Joo, S., Duhon, M., Heller, M., Wallace, B. & Xu, X. 2002, "Dielectrophoretic cell separation and gene expression profiling on microelectronic chip arrays", Anal Chem, vol. 74, pp. 3362-3371.
Innovation and service quality improvement: the added value of a clinical measurement team in a Foundation Trust 1Kemp C, 1Boddy I, 1Chambers IR, 1Marsden S P 1Medical Physics Department, James Cook University Hospital, Middlesbrough, TS4 3BW, UK. Email: [email protected] Background Clinical Measurement is one of the key sections of the medical physics department in the South Tees Hospitals NHS Foundation Trust (STHFT). The staff in this section are Clinical Scientists and Clinical Technologists with backgrounds in Engineering and Physics. We summarise a number of key developments undertaken by the clinical measurement team that have directly benefitted patients and the Trust in order to showcase why this staff group is essential to scientific and clinical progress in the NHS. Methods Four of a number of recently completed projects are described that have improved patient care and both the quality and value of services provided by the STHFT: 1. The development of an electronic system and website for the storage and reporting of home oximetry studies 2. The design, manufacture and commercial exploitation of an ergonomic handle to be used with nebulisers for the treatment of young children with cystic fibrosis. Effectiveness was assessed by way of a questionnaire in a trial involving eight patients. 3. The creation of a comprehensive standard operating procedure and training package for staff carrying out and assisting with urodynamics investigations 4. The design, development and implementation of an eye-brow switch to enable a spinal injuries patient to operate a nurse call and environmental control system Results The benefits realised from each of these projects are: 1. No longer a need to print out reports, saving £2500 per year. Clinicians have immediate access to reports across the Trust, both in Acute and Community settings 2. Supervision of children using the nebuliser handle was significantly reduced. The design of the handle has been registered and commercial opportunities are being pursued 3. We now have less equipment breakages, improved staff confidence and a standardised service across two departments and two sites. Standardising consumables has resulted in a procurement saving as well. 4. An essential assistive device, improving both patient safety and independence Discussion These four projects all required different skills/knowledge and impact on various other departments across the Trust, but have the common outcome of improving the quality of patient care and the services provided. Conclusion Clinical measurement teams within Medical Physics Departments can add significant clinical value and provide a critical mass of expertise across a number of service areas. They can ensure continual service improvement, provide scientific and technical knowhow and implement innovative solutions, working across some of the historical boundaries within and between organisations.
Monday 1st September 2014, 13.45 – 15.15 Diagnostic Radiology Session I – Doses in CT
Results from the 2011 UK National CT Dose Survey – will they make an impact? Edyvean S, Medical (Radiation) Dosimetry Group, CRCE, PHE, Chilton, UK Email: [email protected] Periodic national reviews and surveys concerning frequency and dose for medical and dental x-ray procedures in the UK, conducted over the last 35 years by Public Health England (PHE) and its forerunners, the National Radiological Protection Board (NRPB) (up to March 2005) and the Health Protection Agency (HPA) (up to March 2013), have provided unique insight into national trends in population exposure (Hart et al, 2010)
Continuing advances in computed tomography (CT) technology, including improvements in multi-row detector arrays and computer processing, have facilitated the development of rapid scanning and information acquisition for sub-millimetre sections with almost instantaneous image reconstruction and options for multi-planar and three dimensional (3-D) imaging[4,2,1]. CT examinations have thus become more tolerable for patients, with associated possibilities for increased scanned volumes and potential for repeated exposures. Further developments, for example, in relation to tube-current modulation and image reconstruction, have allowed beneficial improvements in dose, image quality and patient protection[3,6].
The third UK national computed tomography (CT) survey[5] has provided a useful snapshot of patient doses for 2011. Scan details for some 47,000 individual patients (rather than standard protocols as principally studied for the previous national surveys) relating to 13 common types of CT examination on adults, and also head examinations on children, were collected by electronic questionnaires voluntarily submitted by a widely-distributed sample of 182 scanners. This represented nearly a third of all UK scanners, all of which now include multi-detector row (MDCT) technology. Typical practice at each CT centre has been characterised by mean values of the standard dose indices CTDIvol and DLP determined for samples of patients for each examination. Wide variations are still apparent in typical practice between CT centres for similar procedures, highlighting the need for continuing attention to the optimisation of protection and the use of specific scanning protocols for each patient group (with due account of size) and clinical indication, particularly in relation to children.
The report includes summaries of the dose distributions observed and, on the basis of third quartile values for the distributions of typical (mean) doses, presents national reference doses for examinations on adults and children. Separate values are included for high-resolution examinations of the chest using axial-only or helical-only.
Results from this report will be presented. Considerations and effects on both a national and local level will be discussed.
References: 1. Kalender WA (2011). Computed tomography: fundamentals, system technology, image quality, applications. ISBN: 978-3-89578-317-3. Publicis Publishing, Erlangen. 2. Mori S, Endo M, Nishizawa K, Murase K, Fujiwara H and Tanada S (2006). Comparison of patient doses in 256-slice CT and 16-slice CT scanners. Br J Radiol, 79, 56-61. 3. Pickhardt PJ, Lubner MG, Kim DH, Tang J, Ruma JA, Munoz del Rio A and Chen G-H (2012). Abdominal CT with model-based iterative reconstruction (MBIR): initial results of a prospective trial comparing ultralow-dose with standard-dose imaging. AJR, 199, 1266-1274. 4. Prokop M (2005). New challenges in MDCT. Eur Radiol, 15 Suppl 5, E35-45. 5. Shrimpton P, Hillier MC, Meeson S, Golding SJ (2014). Doses from Computed Tomography (CT) Examinations in the UK – 2011 Review, PHE-CRCE-013 6. Tack D, Kalra MK and Gevenois PA (Editors) (2012). Radiation Dose from Multidetector CT (2nd edition). ISBN: 978-3-642-24534-3 (Print). Springer-Verlag, Berlin Heidelberg.
Experience of using Automated Software to perform Patient Dosimetry Analysis 1Burke P, 1Crutchley J, 1Dunn M 1Medical Physics and Clinical Engineering, Nottingham University Hospitals NHS Trust, UK. email: [email protected] Background. This talk describes our experience at Nottingham University Hospitals of the trial introduction of automated software for use in our patient dosimetry programme. Previously, we have conducted a three- year rolling data collection programme [1]. This involved radiographers completing data sheets by hand for 20 patients per exam, and copying the information to a spreadsheet, which was time-consuming and prone to transcription errors. It also required the radiographers to measure or estimate the patients’ weights, and only the data collected from those patients whose weight fell within the limits of a ‘standard-sized patient’ and from a sample with a mean weight of 65 – 75 kg were used. Methods. This talk presents comparisons in data analysis between the previous method and using the automated software, e.g. for: identifying the most commonly performed procedures, calculating the average dose at which an exam is being performed on a scanner, identifying high dose incidents, comparing doses between scanners/centres. Results. The new DoseWatch software (supplied by GE) allows large volumes of patient dose data to be automatically uploaded and analysed very quickly. The direct transfer of data from the CT scanners and the RIS eliminates typing errors and gives us a more complete picture of the dose statistics. This means more meaningful analysis of the data can be performed in a fraction of the time. For example, our experience to date shows that in some cases, exam doses have been underestimated by up to 25% using our previous ‘manual’ system. Dosewatch also quickly identifies high dose examinations, and allows us to filter down into the data to recognise possible systematic causes for these. Discussion. Using the previous Patient Dosimetry method, analysis of data involved completing the three- year programme of paper and electronic data collection from all participating centres, eliminating erroneous data and outliers, ensuring the data fits within the criteria laid out in the guidelines, and comparing average values with other centres and with the relevant Dose Reference Level (DRL) which could take up to two weeks to analyse. Using automated software, this information can be gleaned in seconds. In addition, the pragmatic limitation of 20 patients per exam no longer exists, meaning that much larger amounts of data can be included. This eliminates the requirement to apply weight-restriction criteria on the patient data, and gives a truer reflection of the examinations that are being performed. The software does not currently have all the functionality that we would like to perform the relevant data analysis; however data can be exported to a spreadsheet for further investigation. Conclusion. The use of automated software in the Patient Dosimetry Programme has allowed us to process more data in a much shorter space of time, and glean more information from this data than was previously possible. There are some limitations to its use, but we hope that these will be included in future releases. Key references. 1. Institute of Physics and Engineering in Medicine DRL Working Party. Guidance and Use of Diagnostic Reference Levels for Medical X-Ray Examinations. IPEM Report 88 (IPEM, York) 2004.
Assessment of Radimetrics eXposure software towards establishing patient diameter-specific CT national Diagnostic Reference Levels. 1Cournane S, 2Murphy D, 3Rowan M, 1O Connor U, 3Costello D, 1O’Hare N 1Medical Physics & Bioengineering Dept., St James’s Hospital, Dublin 8. 2Radiology Dept., Our Lady’s Children’s Hospital, Crumlin, Dublin 8. 3Medical Physics Dept., Mater Misericordiae Hospital, Dublin 7. email: [email protected] Background. Diagnostic Reference Levels (DRLs) were first implemented in conventional x-ray exams in the 1980’s, and subsequently for CT in the 1990’s [1]. Recommendations for establishing CT DRLs [2-4] have remained relatively unchanged since, typically based on the 75th percentile of a narrow patient weight range (60-80kg) and on small sample sizes (10 or more). Recent studies have extolled the utilisation of patient diameter- specific DRLs, particularly for paediatric patients [5]; however, such work has not been carried out for the adult scanned population where a range of sizes is evident. The roll-out of the National Integrated Medical Imaging System (NIMIS) in Ireland has meant it is now possible to seamlessly share patient imaging data nationally. Further, this ‘national PACS’ allows for the collation of CT radiation dose metric and patient data, via its Radimetrics eXposureTM software. Accordingly, this study presents an assessment of the eXposureTM software towards establishing local and national DRLs specific to patient diameter, in order to offer a more complete representation of the scanned population. Methods. Data from 26 CT scanners across the National Integrated Medical Imaging System, for all examinations (n=149,784), was captured by Radimetrics eXposureTM over an 18-month period, allowing for the collection of CT scanning parameters including CTDIvol, DLP and effective patient diameter. After data cleansing, diameter-specific 75th parameter percentiles were calculated to inform on establishing local and national DRLs with high volume, high dose and newly established CT exams investigated. Results. Elevated 75th percentiles for DLP and CTDIvol were evident for patients of increased diameter, when compared with normal-sized patient levels, confirming traditional DRLs to be ineffective at identifying higher dose investigative levels for all patients. Newly implemented exams, such as Kidneys-Ureter-Bladder (KUB) examinations showed a significant range for respective diameter ranges, possibly due to inappropriate protocol selection. The data also allowed for the comparison of examination- and size-based CT dose metrics for systems of similar model and manufacturer, in addition to across different manufacturers. Discussion. With such vast amounts of data available in medical imaging, this study presents a more tailored patient- size specific DRL, rather than weight based, which may afford a more effective patient radiation dose monitoring system for all patients. Of particular note were the significant differences in CTDIvol and DLP, respectively, for larger patients (those of increased diameter) across the respective CT scanners, thus highlighting the value of diameter-based dose metric analysis. Conclusion. Data collation software tools can prove useful for establishing DRLs and monitoring CT dose metrics. This work has used one such tool for establishing patient diameter specific DRLs. References. 1. Institute of Physics and Engineering in Medicine (IPEM) (2004) Guidance on the establishment and use of diagnostic reference levels for medical X-ray examinations. IPEM report 88 2. Hart D et al., 2007,HPA-RPD-029; 3. ACR–AAPM practice guideline for diagnostic reference levels and achievable dose in medical X-ray imaging. Revised 2013 (Resolution 47) 4. European Commissions. Radiation protection 109 Guidance on diagnostic reference levels (DRLs) for medical exposure (1999) 5. Goske et al., Radiology, 2013, 268 (1), 208-218
A practical method for estimating scan projection radiograph effective doses in CT 1King L R, 2McGookin PG, 1Castellano IA 1Department of Physics, The Royal Marsden NHS Foundation Trust, London, UK, 2Department of Physics, University of Surrey, Guildford, UK email: [email protected] Background. Dose reduction methods in CT have evolved in recent years, with some manufacturers claiming sub-mSv volume acquisition doses. The scan projection radiograph (SPR), which is necessary for implementing tube current modulation, can therefore deliver a significant proportion of the total exam dose (0.14 mSv for an AP chest SPR [4]). With little information in the literature, a method of calculating SPR doses using readily available software is desirable. Methods. PCXMC (v2.0.1.4) [5] was used to estimate patient doses from default SPR protocols on a 32- slice CT scanner. The fan beam was modelled as several fields 5 mm wide in the z-direction and of varying lengths orthogonal to this, such that the summed fields matched the air kerma profile of the bow-tie filtered beam. The air kerma profile was measured at all four available kVps using the method of Jansen et al [2]. The SPR exposure was then modelled by simulating exposures at 5 mm intervals with the trajectory of the focus describing a line in the superior-inferior direction. Whole body and organ doses were calculated for AP and L-LAT chest-abdo-pelvis SPRs for standard 30 year old adult and 1, 5, 10 and 15-year old paediatric phantoms at each kVp. For validation, adult effective doses were compared with those calculated using a bespoke Monte Carlo program [1] which modelled the same scanner and SPR geometry using a voxel phantom based on that of Zubal et al [6]. The X-ray spectrum and beam shaping filter in this model were in turn validated using dose measurements in a 32 cm PMMA CTDI phantom [3]. Results. Effective doses for AP adult chest-abdo-pelvis SPRs calculated using PCXMC are 0.03, 0.07, 0.12 and 0.17 mSv for 80, 100, 120 and 140 kVp respectively (all at 10 mA; ICRP 60 tissue weighting factors). Effective doses calculated in this way agreed with the Monte Carlo simulation to within ±15% for the adult phantom. SPR doses for smaller, younger phantoms were higher by up to a factor of 1.56, with a 5 year old receiving 0.16 mSv for a 120 kVp AP chest-abdo-pelvis SPR. Discussion. The agreement in effective dose calculated using PXCMC and the Monte Carlo simulation is acceptable considering PCXMC’s Cristy-based geometric phantom and the Monte Carlo program’s voxelised human phantom. Greater discrepancies are expected in organ doses due to differences in organ distributions in the phantoms, with greater uncertainties associated with organs distal from the x-ray beam. Validation between the two models was only possible for the adult phantom. This is presumed to be enough to give us confidence in paediatric results, as there is more scope for differences in organ position and X-ray coverage in larger volume phantoms. Clinical SPR exposure parameters for paediatrics are unchanged from default protocol settings; adjusting SPR scan parameters with patient size is therefore recommended. Conclusion. This technique enables hospital physicists to carry out assessments of patient doses from SPR exposures for specific models of CT scanner using readily available commercial software including compensation for patient size and age. The dose burden from an SPR as a proportion of the entire CT exam dose increases for smaller paediatric patients when using the same SPR exposure factors. Key references. 1. Castellano I A, Dance D R, Evans P M, 2005. CT dosimetry: getting the best from the adult Cristy phantom. Rad Prot Dosim 114(1-3) 321-25. 2. Jansen et al, 1996. Calculation of computed tomography dose index to effective dose conversion factors based on measurement of the dose profile along the fan shaped beam, Br J Radiol 69 33-41. 3. McGookin PG, Calculation of Patient Doses for Scan Projection Radiography in multi-slice CT, MSc dissertation, University of Surrey, 2007 4. Shrimpton et al, Survey of CT practice in the UK. Part 2: Dosimetric Aspects NRPB-R249, Chilton, 1991 5. Tapiovaara M, Siiskonen T, PCXMC – A Monte Carlo program for calculating patient doses in medical x- ray examinations (2nd Ed.). STUK-A 231. Helsinki: Säteilyturvakeskus, 2008 6. Zubal et al, Computerised three-dimensional segmented human anatomy, Med. Phys. 21 (2), 299-302, 1994
A phantom-based characterisation of segmental Organ Dose Modulation on a GE Optima C660 Series CT scanner Dixon M, Loader R, Rowles N Clinical and Radiation Physics, Plymouth Hospitals NHS Trust, UK. email: [email protected] Background: Recent concern from several sources (ACR and RSNA, 2014) (ARSPI, 2014) surrounding CT radiation burden has resulted in contemporary innovation in dose reduction technology. Recent methods include dose limitation to radiosensitive organs in the primary beam, such as breasts. Some authors have expressed concern surrounding the use of breast shields (Huggett, Mukonoweshuro and Loader, 2013) (Foley, McEntee and Rainford, 2013) in reference to their detrimental effect on image quality. More recent techniques such as Siemens ‘X-CARE’ (Siemens Healthcare, 2014)and GE’s Organ Dose Modulation (GE Healthcare, 2014) permit a reduction in tube current when the sensitive organs present to the primary beam. Authors have commented on potential breast dose reduction utilising Siemens X-CARE (Matsubara et al., 2012) but we were unable to find literature on the GE implementation.
Methods: We scanned a CELT (Design Reality, Denbighshire UK) tube current modulation phantom at a variety of noise indices and measured the average Hounsfield number and standard deviation in eight regions of interest. We also measured the dose in a CTDI (PMMA) phantom at each of the eight available peripheral phantom locations in order to characterise the dose distribution with Organ Dose Modulation.
Results: Enabling Organ Dose Modulation reduced the CTDIV (measured in the CTDI phantom) by approximately 20%, whilst increasing the noise (measured in the CELT phantom) by approximately 14%. This is reflected in the dose distribution in the CTDI phantom, where the anterior dose was reduced by approximately 40%, whilst the posterior dose remained largely unaffected.
Discussion and Conclusion. Organ Dose Modulation offered by GE Healthcare is suitable for reducing both organ and effective doses for body examinations, provided practitioners can accept the associated increase in image noise. Currently GE recommend that Organ Dose Modulation is restricted to defined organs, however an optimised approach, pending further investigation, may be to enable it for the entire scan.
Key references. American College of Radiology and the Radiological Society of North America (2014) Image Wisely, [Online], Available: http://www.imagewisely.org/ [10 Apr 2014]. Foley, S.J., McEntee, M.F. and Rainford, L.A. (2013) 'An evaluation of in-plane shields during thoracic CT', Radiation protection Dosimetry, vol. 155, no. 4, March, pp. 439-450. Huggett, J., Mukonoweshuro, W. and Loader, R. (2013) 'a phantom-based evaluation of three commercially available patient organ shields for computed tomography x-ray examinations in diagnostic radiology', Radiation Protection Dosimetry, vol. 155, no. 2.
Matsubara, K., Sugai, M., Toyoda, A., Koshida, H., Sakuta, K., Takata, T., Koshida, K., Iida, H. and Matsui, O. (2012) 'Assessment of an organ-based tube current modulation in thoracic computed tomography', Journal of applied clinical medical physics, vol. 13, no. 2.
The Alliance for Radiation Safety In Pediatric Imaging (2014) Image Gently, [Online], Available: http://imagegently.dnnstaging.com/Home.aspx [10 Apr 2014].
Monday 1st September 2014, 15.45 – 17.15 Professional Session III
So you want to be an MPE? Pearson D As long ago as 1988 the POPUMET regulations required employers to have access to expert advice from a person with an appropriate science degree who is experienced in the application of physics to the diagnostic and therapeutic uses of ionising radiation. Following the publication of IRMER, the Medical and Dental Guidance Notes defined a Medical Physics Expert (MPE) as an HCPC registered Clinical Scientist with an appropriate science degree and 6 years experience in the clinical specialism – so approximately 3 years post registration but with no formal definition of the competences required to act as an MPE.
The revised European Basic Safety Standard Directive (BSSD – EURATOM 2013/59) puts an obligation on member states to put in place and education and training framework and process of recognition by a competent authority for MPEs. This is likely to be brought into UK law in early 2018. At the same time EFOMP developed a framework and curriculum for training MPEs.
In order to develop the education and training framework for MPEs in the NHS in England, the Modernising Scientific Careers programme and Department of Health set up a project team to develop curriculum that mapped to the EFOMP framework and the requirements of the BSSD for MPEs to be involved in optimisation, patient dosimetry and machine surveillance. The curriculum was developed by a group of medical physics professionals and has taken place in close liaison with the Higher Specialist Scientific Training (HSST) project and this MPE curriculum is included in its entirety in the HSST curriculum for Medical Physics.
Working with a range of stakeholders, the project is developing a set of standards for MPEs that recognise that many MPEs work outside the context of the NHS in England. Work is ongoing to tender for the provision of underpinning academic knowledge for the MPE curriculum as part of the tender for the HSST doctoral programme over the summer of 2014. It will be delivered through a 60 credit doctoral level module taught over 2 years. The intention is to upload competences into the on-line assessment tool managed by the National School for Healthcare Science and develop, with the Academy for Healthcare Science, an interim register for MPEs working within the NHS in England until revised UK legislation establishes a competent authority for the recognition of MPEs.
The Scottish Training Scheme Keating D, NHS Greater Glasgow & Clyde, UK Email: [email protected] The new Modernising Scientific Careers training programme for Clinical Scientists (STP) has been running in England since 2011. The final cohort of Scottish Medical Physicists on the four year IPEM Route 1 scheme will complete their training in 2017. This year, NHS Education Scotland (NES) are supporting a new 3.5 year Scottish training programme. Scottish trainees will be eligible to apply for registration as a Clinical Scientist through the Association of Clinical Scientists (ACS) and also through the Academy for Healthcare Science (AHCS) via a "Certificate of Equivalence".
The new Scottish Training scheme is an equivalent programme which encompasses all the key elements of STP but retains the flexibility of previous programmes. A new innovation component of up to 6 months is included and this will train our Medical Physicists to utilise their skills to best effect to impact on the delivery of modern healthcare.
Monday 1st September 2014, 15.45 – 17.15 Biennial Radiotherapy Physics Conference – Quality Control in Radiotherapy
A Synthesis of Process and Indication Type QC Moore R, Royal Marsden NHS Foundation Trust, London Email: [email protected] A brief historical recap leading from early incidents (mostly technical) via introduction of design safety and performance standards [IPEM Report 94] gives the background to this synthesis: that we cannot test all parameters and have responsibilities to test sufficient to report that risk to patient outcome is acceptable hence select what to test and (in contradistinction) what indications we must rely on. The selection implies an associated risk assessment. “Indications” means machine geometry or dose related parameter display/records. This is built on observations that: ● complexity is the price of versatility ● to be a useful, a model of a complex process must be a simplification ○ uncertainty fills the gap between the model and the process ● a risk is a decision to place a stake in order to gain a desirable outcome ● patients’ risk is primarily associated with curative local control and acceptable toxicity ● for safe and successful outcome, we aspire to safe and optimal treatment ● finite healthcare resource implies prioritisation Developments in QA/QC along the ISO 9001 lines involve multi-level document strategy (control, review, approval) to describe and implement procedures. In this way, potential problems may be identified before they manifest. (Draft 2015 makes an explicit risk based cost/benefit recommendation, with the idea that risk opens opportunity and may not be detrimental). Through use of these procedures and discussion, high risk points have been identified such as information transfer whether verbal or procedural (e.g. calibration). For physicists, measurement and prediction of radiation dose and its distribution, together with validation tests, form part of our responsibilities [RP 174 MPE]. This means providing data (over a short term and long term basis) to radiation oncologists, radiographers and other key members of the multidisciplinary team. Actual data examples of QA/QC work will illustrate risk mitigated in linac based QC and internal and external audit scenarios. The opportunity opened by taking these risks is treating higher numbers of more complex cases more regularly or using IGRT techniques with limited capacity or resting fewer patients. The underwriters of these risks at top level need reliable data to assess and allocate resource. Part of the resource goes to train and maintain employees that can exercise authorised competent judgement. Also from this resource allocation, local indication and calibration validations (QC), local internal audit (QA) and collaborative external audit (QA) each provide good value in terms of risk minimisation to patient outcome. External audit may focus on a more specific modality or anatomical site than local QC/QA, but is valuable in testing multiple high risk elements in the (specific) treatment chain. Examples of external audit include the IPEM dosimetry audit network and the NCRI RT Trials QA group. It is recommended external audit is regarded with equal standing in local QA procedures and might act in their stead with local approval and involvement.
A tool to incorporate gamma analysis software into a quality assurance program 1Agnew CE, 1McGarry CK 1Belfast Health and Social Care Trust, Radiotherapy Physics, NICC, Belfast, UK. email: [email protected] Background. Gamma analysis1 is the mainstay for quantifying IMRT and VMAT patient specific quality control. The efficacy of gamma analysis to detect clinically relevant treatment errors has been disputed3,4. However gamma analysis has been found to be an effective, efficient tool readily available on most IMRT/VMAT measurement devices. Despite this widespread use of gamma analysis algortihms, no standardised dataset is available to assess the accuracy of gamma analysis software. Furthermore, it has been found that different devices and software implementations can result in different passing rates for set passing criteria e.g. 3%/3mm 2. We present a suite of test images by which physicists can assess their manufacturer’s software, at commissioning, post service, post upgrade and thus include gamma analysis software into a quality assurance (QA) program. Additionally, the suite of test images provides a frame of reference to compare results reported in the literature from different software versions and different manufacturers. Methods. A suite of three 2D sets of reference and ‘measured’ images were created for this study using DICOM RT plan data and Varian dynamic log files respectively. The suite comprised a simple geometric image with a known gamma passing rate to test the accuracy of the algorithm, a step and shoot IMRT prostate treatment field and a complex head and neck VMAT field both with unknown gamma passing rates to provide clinically relevant insight into the algorithms. Additionally, images were sampled with 1mm pixel pitch and 0.25mm pixel pitch to investigate the sensitivity of algorithms to gamma errors at steep dose gradients. The images were analysed with commercially available software: OmniPro, Verisoft, Delta4, DoseLab and DoseLab Pro using global gamma analysis at 3%/3 mm and 1%/1 mm criterion and a 10% minimum dose threshold. Results. All commercial software accurately measured the gamma of the geometric square at ~ 92%. The results for the clinical treatment field images are tabulated below. IMRT VMAT Gamma 3%/3mm 1%/1mm 3%/3mm 1%/1mm Criterion Pixel Pitch 1mm 0.25mm 1mm 0.25mm 1mm 0.25mm 1mm 0.25mm OmniPro v1.6 99.40 100.00 98.57 98.97 99.93 100.00 91.43 98.89 Verisoft v5.1 99.90 99.60 99.00 98.10 100.00 100.00 97.40 97.60 Verisoft V6.0 100.00 100.00 99.90 100.00 100.00 100.00 98.80 99.40 DoseLab OS 99.10 100.00 98.50 99.80 99.70 99.90 99.30 99.80 DoseLab Pro 6.5 100.00 100.00 99.64 99.92 100.00 100.00 98.18 99.42 Delta 4 2013 100.00 100.00 99.60 99.80 100.00 100.00 98.90 99.40 Discussion. The test image suite in this study revealed gamma passing rates were dependent on the software implementation of the gamma analysis algorithm. The test images provide insight into the gamma software without the compounding factors of fluctuations in linac delivery, variability in detector geometry, detector resolution and set-up uncertainties. Image sampling also affected passing rate, particularly for complex VMAT plans with steep dose gradients. Conclusion. The use of this suite of test images enables gamma analysis software to be incorporated within a QA program. The dependency of gamma passing rates on manufacturer and software versions has been quantified for a simple and complex treatment field. Key references. 1) D. Low et al, Med. Phys, vol. 25, pp. 656-661, 1998, 2) M. Hussein, et al Radiother Oncol, vol. 109, no. 3, pp. 370-6, 2013, 3) B. Nelms et al, Med. Phys., vol. 38, no. 2, pp. 1037-1044, 2011, 4) H. Zhen et al, Med Phys, vol. 38, no. 10, pp. 5477-89, 2011
A methodology for robust, streamlined quality control verification of advanced radiotherapy delivery 1Nash D, 1J. Kearton, 1K. Owen, 1M. Collins, 1N. Shiravand, 1C. Blundell, 1A. L. Palmer 1Medical Physics Department, Queen Alexandra Hospital, Portsmouth, UK. Email: [email protected]
Background. Intensity modulated radiotherapy (IMRT) is a highly complex external beam treatment technique, with many benefits for patients by reducing normal tissue doses whilst allowing the potential for dose escalation [1]. However, due to the complexity of the delivery and potential for serious errors [2], comprehensive quality controls are needed which often takes the form of patient-specific measurements [3]. In general, this is performed with relative dose measurement arrays and absolute point dose measurements [4]. This is time-consuming and may be a bottleneck on the ability to increase patients’ access to advanced radiotherapy [5]. At Portsmouth Hospitals, we have addressed this issue by implementing a robust and streamlined process for verification of the quality of IMRT treatments. Methods. The replacement of routine patient-specific QC has been enabled by the implementation of new quality assurance checks at various stages in the planning process. These stages involve a check on the treatment planning system accuracy, the integrity of the data transfer from the treatment planning system to the record & verify system and the accuracy of the treatment delivery. The planning system check is completed by recalculating the plan with an independent planning system, IBA Compass, whilst the data integrity check is completed by performing a before and after export MU calculation with PTW Diamond software. Lastly the machine delivery is verified using machine QC tests, and delivering reference patients to monitor machine performance. As a full system test, a random selection of clinical plans receive full patient-specific IMRT QC every month. Results. The system has been in place since December 2013, and it has enabled a significant increase the number of patients receiving IMRT from 19% in November 2013 to 41% in February 2014 at Portsmouth Hospitals NHS Trust. We anticipate achieving at least 50% IMRT during 2014. In addition, the new procedure has demonstrated itself as being more sensitive to errors than the previous system. Discussion. The decrease in the QC workload has meant that all patients who would benefit from IMRT would potentially be able to receive it. Conclusion. A new system to safely reduce the patient-specific QC workload at Portsmouth Hospitals has been developed and implemented. Key references. [1] Nutting, C, 2010. ART-DECO Trial Protocol v1. (Cancer Research UK). [2] HPA, 2010. Safer Radiotherapy: Radiotherapy Newsletter of the HPA. Dec 2010, issue 2. [3] IPEM, 2008. Guidance for the Clinical Implementation of Intensity Modulated Radiation Therapy. Report 96. (IPEM: York). [4] Siochi RAC, Molineu A and Orton CG, 2013. Patient specific QA for IMRT should be performed using software rather than hardware methods. Medical Physics, 40(7). [5] Cancer Research UK, 2013. The Radiotherapy Innovation Fund. (Cancer Research UK).
Can log files and complexity scores aid VMAT audit? 1,2McGarry CK, 1Agnew CE, 3,4Hussein M, 5Tsang Y, 1,2Hounsell AR, 3,6Clark CH 1Radiotherapy Physics, Belfast Health and Social Care Trust, Belfast, UK, 2 Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, 3Department of Medical Physics, Royal Surrey County Hospital NHS Foundation Trust, Guildford, Surrey, UK, 4University of Surrey, Guildford, Surrey, UK, 5Mount Vernon Hospital, Northwood, UK, 6National Physical Laboratory, Teddington, UK. email: [email protected] Background. The complexity of radiotherapy has increased in recent years with VMAT utilising a variety of MLC position, dose rate and gantry speed during treatment delivery. Key to safe delivery on a national scale is audit, to ensure the accuracy of delivery. This is typically quantified using detector arrays within a phantom. Another method of quantifying the delivery accuracy is the use of log files1. This work investigates the delivery accuracy of different linear accelerator models using log-file derived MLC positioning errors and the relationship between complexity and results from a detector array following delivery of a 3DTPS plan2. Methods. Seven centres delivered the same ‘Standard’ 3DTPS plan and the log files were analysed following delivery to assess MLC positioning accuracy1. Eight centres created their own 3DTPS plan using their local planning system which introduced variations in plan complexity. This complexity was defined using the modulation complexity score (MCS). These plans were delivered to the PTW 729 detector array in the Octavius phantom and delivery accuracy was assessed using gamma analysis with parameters of 3%/3mm and 2%/2mm. Log files were analysed following delivery to assess MLC positioning accuracy. The correlation between the phantom based delivery accuracy and the complexity (MCS) was assessed across the eight deliveries. Results. Figure 1 shows that the Varian TrueBeam linear accelerators had better MLC positioning accuracy than the 2300 or 2100 models following delivery of the same 3D-TPS plan. This trend continued for the 3D- TPS plans created by each centre although the delivery accuracy, determined using the log files, was not affected by changes in complexity. Figure 2 shows that complexity correlates with delivery accuracy measured using the array. In the two extreme cases; high MCS (low complexity) showed better delivery accuracy and low MCS (high complexity) showed poorer delivery accuracy than the plans with average complexity.
Figure 1 Figure 2 Discussion. Log files are useful in showing differences between different linear accelerator models, particularly when the same plan is delivered on each of the accelerators. Clearly log files can give an insight into delivery accuracy of different accelerators and have the potential to provide a benchmark through audit. Plans with a wide range of complexities were observed even though centres were attempting to achieve the same dose objectives to the same volumetric dataset. Differences in delivery accuracy were seen for plans with different complexities. Conclusion. The MCS clearly has a role for informing centres taking part in VMAT audit as to how complex their plans are and how this may affect the delivery accuracy of their system. Combined with information from the log files, complexity measurement is a useful tool in VMAT audit. Key references. 1) C. Agnew et al, Pract Radiat Oncol. 2014 Jan-Feb;4(1):43-9. 2) M. Hussein et al Radiother Oncol, vol. 109, no. 3, pp. 370-6, 2013.
Pilot dose intercomparisons of 3D and 4D advanced lung radiotherapy 1,2Thwaites D I, 1,3Hansen CR, 1Kafrouni M, 1Caloz M, 1Leturgie Q, 4Corde S, 4Downes S, 1,5Barber J, 1,2Sykes J, 1Juneja P, 1Lehmann J 1Institute of Medical Physics, School of Physics, University of Sydney, Australia. 2Medical Physics, Leeds Teaching Hospitals and University of Leeds, UK. 3Radiation Physics, Odense University Hospital, Denmark. 4Medical Physics, Prince of Wales Hospital, Randwick (Sydney), NSW, Australia 5Medical Physics, Nepean Hospital, Kingswood (Penrith), NSW, Australia email: [email protected] Background. As part of an evaluation of advanced radiotherapy (RT) technology for the NSW Health Department, the Institute of Medical Physics (Sydney University) and partners have developed and carried out some pilot intercomparisons of planning and ‘treatment’ delivery for lung treatments, including the use of FFF beams, VMAT, SBRT and 4D RT, across a range of treatment planning systems (TPSs), delivery systems and techniques. There are few, or no, reported audits/intercomparisons of many of these combinations, thus this work provides initial testing of potential audit methods, with the developments linked with the Australian RT clinical trials (TROG) QA group and the national RT dosimetry audit system (ACDS:ARPANSA). Methods. Four main pieces of work have been involved, mainly on 6MV beams: i) An SBRT planning study across 6 combinations of linac (Elekta Agility, Varian Truebeam, Novalis, Tomotherapy) and TPS (Eclipse, Monaco, Pinnacle and Tomoplan), using FFF and FF beams. Three lung patients were used, with targets a) close to chest wall, b) close to bronchial tree and c) more central in the lung; Evaluation was via plan comparison, including acceptability to the NSW SBRT protocol requirements. ii) Testing consistent delivery of some of these plans to a single Arccheck, taken to the various RT centres involved. Evaluation was via agreement between plan and measurement (3%, 3mm on distribution, 3% on isocentre dose); currently ongoing. iii) An end-to-end test of 4D planning and delivery in 5 centres following their current standard aproaches (different CT-sims, 4D methods, TPSs, planning methods, linacs and delivery techniques), using an in-house (Prince of Wales Hospital, PoWH) developed 4D thorax phantom, with mobile lung ‘tumour’, moving with variable amplitude and speed. This initially held a small ion chamber and was used with a 5% tolerance. iv) From the latter pilot, the methods were extended with the aim of testing dose distributions over the same range of 4D methods and RT centres, using a modified target holding radiochromic film in multiple planes. This is under initial testing currently in PoWH. Results. i) SBRT planning: for all system combinations, differences in plan quality between FF and FFF were small. The most significant observation between centres related to minor protocol violations (MPV), showing correlation with clinical SBRT VMAT experience (most experienced centres: 0.6 MPVs per plan on average; limited experience centres, 3.8 MPV per plan); ii) SBRT delivery to Arccheck: initial results indicate high gamma passing rates, but some average differences in absolute doses. These are being investigated and the number of centres extended. iii) 4D, ion chamber: all results were within the pre-determined 5% tolerance, regardless of equipment, methods or techniques (3DCRT, IMRT, VMAT). iv) 4D, film: static and small amplitude movement deliveries pass dosimetric testing at acceptable levels; however more significant problems are observed for greater amplitudes of motion. These are largely resolved when the static plan is convolved with the measured motion. Thus the phantom and measurement methods have been verified in principle, although still undergoing further refinement before being taken out in the field to other centres. Discussion and Conclusion. This work provides initial testing and feasibility/pilot studies of audit/intercomparison phantoms and methods for 3D and 4D advanced RT treatments. This is initially mainly for lung treatment but is linkable to other intercomparison studies carried out for IGRT, etc. Once each system has been tested, it is gradually being utilised across RT centres in NSW to test accuracy, precision and consistency of the implementation of those RT methods, providing confidence to users. Given the link to national systems, this work may also have potential for use as the basis of national audits, or to inform their development.
Monday 1st September, 15.45 – 17.15 New applications in rehabilitation and movement analysis
A novel device for testing the dynamic performance of in situ force plates 1East R, 1One Small Step Gait Laboratory, Guy’s Hospital, London, UK email: [email protected] INTRODUCTION and AIM Confidence in the output of force plates is integral to gait analysis. Force plates are calibrated by manufacturers under different conditions to those relied upon clinically. The project created a system that could be used to dynamically calibrate force plates, in situ, against a theoretical solution; hence minimising the induction of error within the calibration process. The proposed solution involved the design and development of an eccentrically loaded wheel mounted on a weighted frame.
MATERIALS and METHODS The frame was designed to hold a quick release Invacare wheel mounted in 2 orthogonal positions (Fig 1). Lead masses add weight so that the overall dynamics of the system better simulate that of paediatric gait. Castor wheels allow the device to be wheeled onto force plates and secured. The overall static weight of the system is 37.2kg. s Fig 1: The device - showing both wheel The wheel is placed on the force plate and spun. A orientations VICON motion analysis system captures the positional data of the markers placed around the rim of the wheel. A marker was placed on the eccentric mass at the rim; this marker defines the velocity of the mass and the direction of the centripetal force. Data were processed using Matlab (Fig 2). Force plate and centripetal force data were superimposed, and the RMS error calculated.
RESULTS For nine trials conducted, the RMS error between the 2 simultaneous measures of force was calculated. The Fig 2: An example figure generated by the Matlab script results are displayed in table 1. The difference between for each of the x, y and z directions. The red line is the the force measurements in the x and y directions were force plate data, the blue is the calculated centripetal under 1.5N. The difference in the z direction was under force. 5.5N.
DISCUSSION and CONCLUSIONS The difference between the two force measurements is approximately 2% in each of the directions. It is difficult to assign the difference to an error in either measurement. The theoretical centripetal force calculation relies on the calibration of the VICON system; the cameras are calibrated to 0.01mm Table 1: The average difference between the 2 precision. The markers used were 14mm in diameter – 0.07% forces measurements over 9 trials error. This error is then enhanced in the processing of the data. The force exerted by the mass is approximated by dividing the mass into finite elements and the force exerted by each element is calculated and then summed to calculate the centripetal force. A finer division of the mass may improve the precision of the measurement. However, these sources of error are considered insignificant in comparison to the error induced by the uncontrolled movement in the system.
Assessment of cervical range of movement during simulated extrication from a motor vehicle using CODA and XSens measurement systems 1 Hart D, 2 Hillman M, 3 Sparke A, 2 Harris N 1 Clinical Measurement Department, Royal National Hospital for Rheumatic Diseases, Bath, UK. 2 Designability, Royal United Hospital, Bath, UK. 3 South Western Ambulance Service NHS Foundation Trust, Exeter, UK. Email: [email protected] Background: We have developed a novel cervical immobilisation device (Necksafe) for use following trauma. Assessment of resulting Cervical Range Of Movement (CROM) of the prototype against a market leading design of neck collar during real world conditions presents a considerable challenge. We carried out CROM measurements in a simulated trauma environment using a ‘gold standard’ active optical marker tracking system, CODA (Charnwood Dynamics, UK) and an ambulatory inertial measurement system, XSens MTw (Xsens Technologies, Netherlands). Methods: Following ethical approval, 4 members of the public acted as mock casualties during extrication from a motor vehicle by ambulance and fire and rescue personnel. A dual detector CODA system was used with 6 markers applied each to head and trunk (10Hz). Due to the potential for marker occlusion during extrication, a second independent measurement system was also used in which XSens orientation sensors were affixed to head and trunk (20Hz). Whilst these sensors would have some susceptibility to drift and magnetic disturbance, by combining the measurement data it was intended to permit assessment of CROM throughout the extrication. Analysis: Following export of data from proprietary software, all data processing was competed using Microsoft Excel with quaternion analysis implemented by visual basic macros. An algorithm to utilise marker redundancy during occlusions was developed. Coordinates of all CODA markers were exported in cartesian format using CodaMotion v6.79.3 software. Static measurements, free of marker occlusions, were used to calculate the orientation of all 3 marker combinations (20 permutations) that would define either the head or trunk orientation. A relative translation between each of these and the static orientation of the XSens head sensor was then computed. At each measurement sample, a macro identified a combination of 3 in-view markers and looked up and applied the appropriate relative translation such that the resulting orientation appeared within the XSens coordinate system. XSens MTw sensor orientations were exported using MT Manager v4.1.5 software. Relative Euler angles between head and trunk orientation were calculated for both measurement systems corresponding to a sequence of forward flexion, rotation and lateral flexion of the head to the trunk. Results: Implementation of the marker redundancy algorithm during occlusions increased the mean percentage of time for which there was usable CODA data from approximately 50% to 65%. Marker occlusion was more prevalent than expected and generally coincided with movement of the participant i.e. at time points of greatest interest during the extrication. XSens data was available throughout the extrication however larger than expected orientation changes of the trunk sensor were noted. Reviewing video and photographic extrication recordings, this appeared attributable to sensor movement on top of the clothes when gripped and handled by personnel. Magnetic disturbance could also have potentially formed a component of the artefact. Discussion: Limitations in the use of the described measurement systems were highlighted during the study. Steps to mitigate these can be taken however. We successfully developed an algorithm to utilise CODA marker redundancy during occlusions and were able to derive joint angles between body segments from XSens orientation data. Data analysis also informed techniques later applied to laboratory based measurements of extremes in CROM. Conclusion: Using the adopted method under the described conditions, neither measurement systems permitted accurate measurement of CROM. Issues of sensor occlusion (CODA) and sensor movement (XSens) appeared to prevent this. With marker redundancy, occlusion of CODA markers can be overcome using the developed algorithm, provided occlusion of the marker set is only partial. When measuring small relative movements using XSens, careful consideration of sensor placement and fixation relative to anatomy, not clothes, is needed if measurements are to be meaningful to the underlying skeletal movement.
Comparison of three low-cost motion analysis devices for use in dynamic visual acuity testing 1Ayers M, 2Corcoran J, 2Shortland A 1King’s College Hospital NHS Foundation Trust. 2Guy’s and St Thomas’ NHS Foundation Trust. email: [email protected] Background: The vestibulo-ocular reflex is vital for the maintenance of clear vision during movements of the head [1]. People suffering with problems associated with their vestibulo-ocular reflex often experience nausea and dizziness [2]. This can have a significant and detrimental effect on their lives [3]. It is therefore important to be able to accurately diagnose such problems. Current dynamic visual acuity tests however, suffer from a number of shortfalls. Arguably, the most significant of these is the inability to ensure that the head of the patient is moving at a sufficient rotational velocity to isolate the vestibulo-ocular reflex [3]. As a consequence, results from such tests are often disregarded by healthcare professionals. It was suggested by Herdman et al [4] that, during testing, the head should be moving between 120 and 180 deg/s (a 60 deg/s range). A number of motion analysis devices capable of measuring angular head velocity were validated against an established motion analysis system. If shown to be sufficiently accurate, the use of such devices could help improve the credibility of dynamic visual acuity testing. Methods: An established 7-camera Vicon MX motion analysis system was used to validate three low-cost motion analysis devices. These were an OptiTrack V120:Duo, a NaturanPoint Track IR 5 and a Samsung Galaxy S3 smartphone. Angular position data was captured using all devices simultaneously during a single trial. This trial involved the cyclic rotation of a custom built dummy head device. These rotations were instigated by an experienced vestibular physiotherapist at a displacement and frequency designed to replicate the upper limit of clinical testing. From the angular position data recorded by each device, the angular velocity of the dummy head device was derived and processed using a 2nd order low-pass Butterworth filter. Comparison of each of the three low-cost devices with the Vicon system was done using Bland-Altman plots. Results: Relative to the angular velocity derived from the Vicon motion analysis system, the difference in angular velocities recorded by the V120:Duo, the Track IR 5 and the Galaxy S3 had standard deviations of +/- 4.1, 9.2 and 15.8 deg/s respectively. Discussion: The standard deviations of the differences between the Vicon and each of the low-cost motion analysis devices are all small compared to the range of angular velocities at which the vestibulo-ocular reflex is isolated. Thus, all devices are potentially suitable for the measurement of angular head velocity during dynamic visual acuity testing. The V120:Duo, out of the three devices, performed best. This is perhaps unsurprising given that it was, at around £2,000, the most expensive. The Track IR 5 also performed well. This device has the advantage of costing under £150. The Galaxy S3 demonstrated inferior performance to the dedicated motion analysis devices. A smartphone would however benefit from its small size and availability. Conclusion: All three devices demonstrated performance that is within the limit required to isolate the vestibulo-ocular reflex. To assess the broader suitability of these devices in a clinical environment, additional testing under different conditions is suggested.
[2] M. A. Gresty, K. Hess, and J. Leech. Disorders of the Vestibulo-Ocular Reflex Producing Oscillopsia and Mechanisms Compensating for Loss of Labyrinthine Function. Brain, 100:693_716, 1977. [1] G. E. Grossman, R. J. Leigh, E. N. Bruce, W. P. Huebner, and D. J. Lanska. Performance of the Human Vestibulo-Ocular Reflex During Locomotion. Journal of Neurophysiology, 62(1):264_272, 1989. [3] S. J. Herdman. In Vertigo and Imbalance: Clinical Neurophysiology of the Vestibular System, Handbook of Clinical Neurophysiology, Volume 9, Chapter 14. Elsevier, 2010. [4] S. J. Herdman, R. J. Tusa, P. Blatt, A. Suzuki, P. J. Venuto and D. Roberts. Computerized Dynamic Visual Acuity Test in the Assessment of Vestibular Defects. The American Journal of Otology, 19:790- 796,1998.
The Stroke Vision App: Assessment of Visual Impairment in Stroke Survivors 1,2 Tarbert C M, 2 Livingstone IAT, 1 Weir AJ 1 Medical Devices Unit, NHS Greater Glasgow & Clyde, Glasgow, UK 2 Glasgow Centre for Ophthalmic Research, NHS Greater Glasgow & Clyde, Glasgow, UK email: [email protected] Background. In the United Kingdom, stroke is the leading cause of adult disability [1]. Complications in stroke survivors are wide-ranging (e.g., communication problems, motor deficits) and a similarly broad variety of interventions are required to aid rehabilitation [2]. Up to 66% of survivors will experience visual problems [3], however, in many cases, their vision is not adequately assessed [4]. An unrecognised visual defect is a common barrier to rehabilitation progress, and their effective detection and management is therefore an important factor in optimising a patient’s outcome [5]. In this paper, we describe a novel, tablet- based application (app) to act as a screening tool which (a) provides a rapid and accurate assessment of gross visual deficits in stroke survivors, (b) can be used at the bedside by non-specialist staff at the acute stage, (c), provides a means of integrating the results into the patient’s e-record, (d) provides clear information to patients and carers about the identified visual defects and their implications and (e) harnesses the features of touchscreen technology to aid testing in stroke patients with concurrent morbidities (poor vision, decreased fine motor control, comprehension difficulties). Methods. A subset of high value assessments targeting some of the most common visual problems associated with stroke has been incorporated into the app. These include a ‘Tumbling E’ acuity test, suitable for patients who suffer from receptive and/or expressive aphasia, and a visual field test to detect the field deficits characteristic of stroke (hemianopia, quadrantanopia). Two custom tests of spatial awareness have been developed and are included to aid in the diagnosis of visuospatial neglect, a perceptual disorder. Education modules are included to provide information to patients and carers as well as a novel tool for demonstrating visual deficits; StrokeSim. Education modules targeting staff who may not have specialist ophthalmic knowledge are also provided. A facility for e-mailing the screening results to a secure server, ready for inclusion in the patient’s electronic record is also included. The app has been developed for a 10.1" tablet running the Android version 4.0 and above, and includes support for encryption to ensure security of the patient results database. Results and Discussion. The Stroke Vision app is currently undergoing informal user testing to refine the app interface and assessments. The users in this context are health professionals, stroke survivors and carers, and feedback from all three groups has been sought. Formal validation testing of the assessment portion of the app will follow, and local ethics approval is being sought for that purpose. This will be submitted in parallel with a notification to MHRA for use of a non-CE marked medical device in a clinical trial for conformance testing; the first step in CE-marking the app as a Class I medical device. Conclusion. The Stroke Vision app is a low-cost, flexible solution to the currently limited assessment of visual stroke. It provides simple, user-friendly tools for visual acuity, visual fields and visual neglect testing, improved means of recording and reporting results, and importantly, new tools for communicating the implication of those results to patients and staff alike. Once the validation process is complete, we anticipate it will provide a powerful tool for assessing visual stroke and ultimately improving rehabilitation outcomes. Key references. [1] J. Mackay, The Atlas of Heart Disease and Stroke, 1st edition, World Health Organization, 2004. [2] SIGN, Management of patients with stroke: Rehabilitation, prevention & management of complications & discharge planning. A national clinical guideline, 2010, ISBN: 978-1-905813-63-6. [3] C. Macintosh, Stroke revisited: visual problems following stroke and their effect on rehabilitation, British Orthoptic Journal, 2003; 60: P1- 14. [4] Scottish Government, Better Heart Disease and Stroke Care Action Plan, 2009, IBSN: 978-0-7559-8067- 3. [5] University of Glasgow College of Medical, Veterinary and Life Sciences, Best Practice Statement: Screening, assessment and management of vision problems in the first 30 days after an acute stroke, http://www.glasgow.ac.uk/bpsvision, 2013.
Dynamic Facial Imaging Analysis For Oral-Facial Surgery Assessment 1Ju X, 2Ayoub A, 3Khanbay B 1Medical Devices Unit, Department of Clinical Physics and Bioengineering, NHS Greater Glasgow and Clyde, UK. 2Dental School, College of MVLS, University of Glasgow, UK. 3 Disciplines of Orthodontics and Paediatric Dentistry, Faculty of Dentistry, The University of Hong Kong, HK. email: [email protected] Background Dynamic imaging is a recent innovation of stereo photogrammetry which allows capturing 3D facial animations at a rate of 60 frames per second [1]. This generates hundreds of 3D images for analysis. The technique has enabled extraction of motion curves of sparse or dense facial landmarks of facial animations which allows dynamical assessment of the facial soft tissue following oral-facial surgery. This study describes the process of “automatic landmark tracking” and presents a comprehensive approach for the analysis of facial animations.
Methods Groups of volunteers were recruited for validation of the automated landmark tracking and facial animation reproducibility study. Facial landmarks were manually landmarked by trained operators on the first frame of the 3D image sequences and the landmarks at the first frame were automatically tracked in the rest frames of the 3D image sequences by facial landmark tracking software. The accuracy of automatic landmark tracking was investigated by comparing the automatic tracked landmarks with manually tracked landmarks. The reproducibility of facial animations was investigated in terms of magnitude, speed and similarity. Patients of oral cancer, cleft and facial paralysis were recruited for dynamic facial animations analysis. The facial animations of patients were analyzed by comparing their animations with that of volunteers’ facial animations in order to quantify their dynamic facial anomalies in terms of magnitude, speed and asymmetry score.
Results The automated facial landmark tracking across the facial animations was within 0.5mm accuracy. Dynamic capture has shown reproducibility of facial animations. Cancer surgery decreased the magnitude of lip movements and reduced the speed of facial animations. Asymmetry of lip movements were detected in cleft and facial paralysis cases.
Conclusion Dynamic facial imaging has been demonstrated as a reliable method for the objective evaluation of facial animations.
Key references [1] Urquhart CW, Green DS, Borland ED. 4D capture using passive stereophotogrammetry. Visual Media Production 2006; CVMP2006:196.
A simple device for monitoring self-actuated movement in bed-bound patients Perring S and Summers A, Poole Hospital NHS Foundation Trust, Poole, Dorset BH15 2JB Email: [email protected] INTRODUCTION Bed sores are a major source of morbidity and mortality in bed-bound patients1,2. Avoidance of tissue wounds is a priority because treatment of bed sores once developed is complex, intensive and expensive. Pressure must be relieved regularly and for an extended period in order to avoid disruption of skin tissue. If patients can be proved objectively to be relieving skin pressure by moving themselves in bed without intervention by staff or carers, expensive interventions such a regular turning by staff or air mattresses can be avoided. MATERIALS and METHODS A simple device for monitoring changes in a patient’s weight bearing location was developed. The system was based on an Arduino Mega microcontroller (www.arduino.cc). Up to 5 commercial pressure sensing pads (TABS fall monitoring pressure pads, Stanley Healthcare, USA) were placed under the patient’s posterior separated by 5cm in the manner indicated in the illustration below. Typically 3 such sensors were enough to cover the whole potential movement of the patient’s buttocks. The sensing pads were used as transducers to provide signals to the digital input channels of the Arduino. Any change in status of the sensing pads was detected and the sensor status of each sensor recorded along with the time from an attached real-time clock saved on an attached SD card reader-writer in a comma separated value text file. The unit was tested on a normal volunteer for a number of overnight periods with an infra-red camera also installed to record any movement by the volunteer while asleep. The unit was also installed on 4 patients for an extended overnight period. Staff on the ward were required to record on a paper diary the times of any interaction with the patient when they physically moved the patient for whatever reason.
RESULTS Testing on a normal volunteer indicated a one-to-one correlation between movements detected with the pressure sensors and significant movements identified in the video stream. 3 of the 4 patients on whom the system was tested showed no movements detected during the recording period except when the staff had recorded an interaction involving patient movement. The remaining patient showed significant numbers of self-actuated movements independent of the staff interventions. CONCLUSIONS Results suggest that recording of patient self-actuated movement using pressure sensors under the patient and a simple recording device can be effective in determining if patients can self-actuate tissue preserving movement REFERENCES 1. Redelings MD, Lee NE, Sorvillo F. Pressure ulcers: more lethal than we thought? Adv Skin Wound Care. 2005 Sep;18(7):367-72. 2. Clark M, Bours G, Defloor T (2002) Summary report on prevalence of pressure ulcers. EPUAP Review, 4 (2) 49-57
Monday 1st September 2014, 15.45 – 17.15 Diagnostic Radiology Session II – Fluoroscopy and General Topics
An update from the evidence based QA working party – fluoroscopy data collection and results 1Worrall M 1Radiation Physics, NHS Tayside, Ninewells Hospital, Dundee, UK. email: [email protected]
Aim The evidence based QA working party aims to compile a large data set of QA results from all diagnostic radiology equipment. The purpose is to develop a quantitative evidence base to assess the usefulness of the current range of tests recommended in IPEM reports 91 and 32, as well as the appropriateness of the tolerances. The data will feed into future updates of these reports.
Specifically under consideration in this presentation is the data collection for fluoroscopy systems. It is intended that in addition to assessing the usefulness of the current range of tests, the large data set could be used to establish updated ‘expected ranges’ for detector dose rates, threshold contrast detail detectability results etc.
Methods An Excel spreadsheet pro-forma has been developed for large scale fluoroscopy data collection. Every test from IPEM reports 91 and 32 is included, along with several additional tests that the members of the evidence based QA working party felt were being widely performed.
The pro-forma has been extensively tested by the working party; variations in local fluoroscopy test methods mean that there have been compromises made in the data collected. However, it is believed that the pro- forma will gather enough test data as to allow for significant data collection and meaningful analysis.
Results The finished pro-forma is set to be released into the diagnostic physics community via the Medical Physics and Engineering mailbase. This will be in late September, following the completion of the data collection phase for Automatic Exposure Control devices.
Discussion The pro-forma will be presented at MPEC during this session. The reasoning behind the data being collected will be discussed, as will the compromises made where there is more than one way of collecting or analysing data. There will be some instruction given on how to fill in the pro-forma. Finally, the key intentions of the analysis to come will be discussed.
Survey of measurement uncertainties in routine fluoroscopic quality control 1Robinson M, 1Munson K, 1Dunn M 1 Medical Physics and Clinical Engineering, Nottingham University Hospitals, UK. email: [email protected] Aims/Objectives Quality control on fluoroscopy x-ray imaging systems involves making measurements of radiation quantities, for example dose-area-product (DAP), radiation output or x-ray tube potential using specialist testing equipment. Each measurement is then compared to some expected value, or a baseline value to determine whether it is within tolerance. A quality assurance report is prepared by medical physics staff that is sent to the radiology staff. It is important to ensure that the values reported to the customers together with the tolerances applied to these values are based on sound metrology.
Methods This work used a standard, methodical approach to determine the sources and magnitudes of uncertainties at each point in the chain from measurement, calculation or conversion to reporting values. Uncertainties were assessed using a variety of sources: test equipment documentation, critical evaluation of measurement technique, analysis of calibration factors or correction factors, assumptions made about the physical processes present. The estimated uncertainties were combined using a standard propagation of errors method.
Outcomes Once we are aware of the measurement uncertainties, we have several choices of how to deal with them. We could accept the uncertainty, minimise the uncertainty by measuring in a different way or using different equipment or report a different metric. For example, the measurement uncertainties in the calculation of dose-area-product were assessed to be 9%. The calculated value of DAP is compared to the value given by the DAP meter within the x-ray equipment. The value reported to our customers is the percentage difference between the measured and calculated dose-area-product. The uncertainty on this reporting metric is 9 percentage points (using propagation of errors). The IEC remedial level on DAP is 25% however our local action level is 10%. Does a different reporting metric need to be developed? Is it sensible to use the 10% action level? Could we use an external DAP meter for our measurement? Should we use a beam of known size e.g. collimate to an object instead of measuring the beam dimensions on a CR image? Could we measure dose at the same point as field size to avoid distance correction errors?
Relevance/Impact This work has pinpointed sources of uncertainty in our measurements and informed improved testing, data analysis and reporting methods. We now have confidence in our measurements and our customers have reports that are consistent with the measurement techniques used.
Discussion This step-by-step method of approaching uncertainties estimation can be applied to any radiation measurement system in order to improve the scientific validity of the reporting statements on a medical physics quality assurance report. We would recommend services adopt this approach when developing or reviewing QA processes.
Use of Contrast Curves and Image Quality Factor for Assessing System’s Performance in Fluorosocpy 1Priba L, 1Worrall M, 1Sutton D 1Medical Physics, NHS Tayside, Dundee, UK. email: [email protected]
Background. Threshold Contrast Detail Detectability (TCDD) test objects, such as TO.10 from Leeds Test Object family, are most commonly used for assessment of overall performance of fluoroscopy systems. Images of TO.10 can be used for qualitative assessment of imaging performance of fluoroscopy systems. A quantitative comparison of multiple systems operating at different entrance air kerma rates and FOVs is more challenging and problematic. For many years contrast curves were used as reference data for between- system comparisons. However, the latest reference data from 2004[1], may no longer describe a finely tuned system and newer systems may still show satisfactory performance even when deteriorating. Another approach, proposed by Gallacher et al.[2], introduced a single quantity, Image Quality Factor, as a more comprehensive indicator of system performance. This work focuses on discussing how both methods can be used for between-system comparison of TCDD and establishing of local standard reference curves.
Methods. Data from routine TCDD survey results for image intensifier systems was obtained and used to plot contrast curves. Image quality factor for each system was calculated using most recent standard reference data using approach described in Gallacher et al.
Discussion. Between-system comparisons revealed inconsistencies in TCDD testing conditions across tested systems. Testing conditions consistency is necessary for deriving local reference curves. In addition, false conclusions can be drawn from contrast curves if data is not normalised to a relevant reference curve. Using Image Quality Factor can further increase confidence in use of contrast curves for between-system comparisons.
Conclusion. Our study shows how correct data normalisation is necessary for appropriate interpretation of contrast curves and how establishing more up-to-date local reference curves may be necessary for accurate comparison of performance of fluoroscopic systems. Recommendations for new testing protocol were made to allow calculations of local reference curves.
Key references. [1] Evans, D. S., et al “Threshold contrast detail detectability curves for fluoroscopy and digital acquisition using modern image intensifier systems.” Br J Radiol 77.921 (2004):751-758. [2] Gallacher, D. J., et al. “Use of a quality index in threshold contrast detail detection measurements in television fluoroscopy.” Br J Radiol 76.907 (2003):464-472.
An investigation of automatic exposure control calibration for chest imaging with a computed radiography system Moore C S1, Wood T J1, Avery G2, Balcam S2, Needler L2, Beavis A W1 and Saunderson J R1 1Radiation Physics Department, Queen’s Centre for Oncology and Haematology, Castle Hill Hospital, Hull & East Yorkshire Hospitals NHS Trust, Castle Road, Hull, HU16 5JQ, UK 2Radiology Department, Hull & East Yorkshire Hospitals NHS Trust, Castle Hill Hospital, Castle Road, Hull, HU16 5JQ, UK email: [email protected] Background. In the UK, the IPEM have published a standard for testing digital imaging systems but they accept there is no universally agreed metric for calibrating an AEC device for use with digital detectors. The purpose of this study was to examine the use of three physical image quality metrics in the calibration of an automatic exposure control (AEC) device for chest radiography with an Agfa computed radiography (CR) imaging system. Methods. The metrics assessed were signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and mean effective noise equivalent quanta (eNEQm), all measured using a uniform chest phantom. Subsequent calibration curves were derived to ensure each metric was held constant across the tube voltage range. Each curve was assessed for its clinical appropriateness by generating computer simulated chest images with correct detector air kermas for each tube voltage, and grading these against reference images which were reconstructed at detector air kermas correct for the constant detector dose indicator (DDI) curve currently programmed into the AEC device. All simulated chest images contained clinically realistic projected anatomy and anatomical noise and were scored by experienced image evaluators. Results. Resulting calibration curves are shown in figure 1(a) and the subsequent optimally shaped curve is shown in figure 1(b). 3
4 2.5
3.5 2 3 Constant DDI 2.5 Constant eNEQ 1.5 Constant SNR 2 Constant CNR 1
1.5 Detector Air Kerma (µGy) Kerma Air Detector
Detector Air Kerma (µGy) Kerma Air Detector 1 0.5
0.5 0 0 40 60 80 100 120 140 40 60 80 100 120 140 Tube Voltage (kV) Tube Voltage (kV) Figure 1: (a) resulting calibration curves and (b) optimally shaped curve. Image evaluator results demonstrated a curve based on constant CNR is not optimal given that all 60 kV images were not clinically acceptable and detector air kerma (DAK) at high tube voltages were higher than required. Curves based on constant SNR and eNEQm returned adequate image quality for appropriate DAKs across the tube voltage range. The curve currently programmed into the AEC (constant DDI) cannot be optimum given that it increases DAK at low tube voltages; the curve does not take into account contrast loss and photon loss as mean energy increases. Discussion. Based on these results, the optimally shaped curve for calibrating an AEC device for chest radiography is one based on a constant SNR as demonstrated in figure 1(b). The magnitude of DAKs at each tube voltage is of course dependent on the image evaluators’ preference, and therefore subjective. Although curves derived measuring SNRs may seem simplistic, the medical physicist is tasked with the optimization of AECs without phantoms that contain anatomy. However, we have demonstrated the use of a simple phantom to derive curves that will produce clinically adequate chest image quality across the tube voltage range. Conclusion. This work has investigated the derivation and validation of AEC calibration curves for chest imaging with a CR system. AEC calibration curves were derived with a simple phantom. Curves based on a constant SNR provide adequate image. It is important the value of the calibration DAK is chosen carefully with cooperation of image evaluators. Key References. CS Moore et al, “An investigation of automatic exposure control calibration for chest imaging with a computed radiography system”. Phys. Med. Biol. 59 (2014) 2307-2324.
Tuesday 2nd September 2014
Tuesday 2nd September 2014, 08.45 – 09.30 IOP Plenary
Medical need, large group studies and emerging opportunities for advances in MRI and PET imaging Matthews P M, OBE, MD, DPhil, FRCP, FMedSci, Head, Division of Brain Sciences, Department of Medicine, Imperial College, London, E515, Burlington Danes, Hammersmith Hospital, DuCane Road, London W12 0NN UK email: [email protected] Imaging technology capabilities have expanded rapidly over recent decades. Particular advances have been made in the last decade based on the use of new signal processing and image analysis approaches. However, imaging technology also has advanced and the range of applications broadened. The potential for ultra high field human imaging to contribute to diagnosis or monitoring of neurodegenerative and musculo-skeletal medicine and functional neurosurgery will be highlighted. The opportunities for integrated MRI-PET systems in both brain and tumor imaging will be discussed, as well as the opportunity to improve sensitivity in PET with design of systems with more efficient photon capture. A particularly exciting development has been the application of MRI to large, population based imaging for epidemiology, such as the UK Biobank Imaging Enhancement. Throughout, the discussion will emphasise an end user’s perspective and the challenges that are being addressed- or need to be addressed- in order to deliver the full promise of the methodology.
Tuesday 2nd September 2014, 09.30 – 11.00 Update Scientific Session (Physical Agents, RPA)
European Union Physical Agents (EMF) Directive Update Keevil S, Guy’s and St Thomas NHS Foundation Trust and King’s College London Email: [email protected] Many members of the medical physics community will be aware of the problems posed by the European Union (EU) Physical Agents (Electromagnetic Fields) Directive (2004/40/EU) [1, 2], and of the campaign to mitigate its impact [3, 4]. The purpose of this paper is to bring colleagues up to date with developments, and to explain what remains to be done as the issue draws to a conclusion.
The 2004 directive was due to be implemented by 30th April 2008. In 2007, following intense lobbying, the European Commission announced postponement of this deadline by four years. Then, in June 2011, the Commission proposed a new directive, in which EMF exposure limits would not apply to MRI workers and safe working practices would instead be developed to ensure health and safety in MRI. This proposal was opposed by several EU member state governments, and in April 2012 a further implementation delay of 18 months was announced.
Following another year of negotiation, a new EMF directive (2013/35/EU) was adopted by the EU on 11th June 2013 [5, 6]. This new directive retains the exemption (or derogation) from EMF exposure limits that was a key feature of the 2011 proposal. However, the wording regarding the scope and conditions of this derogation is ambiguous, reflecting an attempt to reconcile the contrasting positions held by member states. This may result in different legal interpretations in different European countries.
The deadline for implementation of the new directive is 1st July 2016. Before then, the European Commission will issue a non-binding practical guide, which may help to resolve the ambiguities in the directive. Public Health England (PHE) has been commissioned to produce this guide, which is currently in draft form. PHE is working closely with a group drawn from relevant international organisations including EFOMP, ISMRM and ESMRMB. National authorities are also carrying out their own preparations, and in the UK the Health and Safety Executive is working with MRI community organisations (including IPEM) to develop guidance.
1. Directive 2004/40/EC of the European Parliament and of the Council. Online at http://eur- lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2004:159:0001:0026:EN:PDF (accessed 18th August 2014). 2. Keevil SF, Gedroyc W, Gowland P, Hill DLG, Leach MO, Ludman CN, McLeish K, McRobbie DW, Razavi RS, Young IR. Electromagnetic field exposure limitation and the future of MRI. Br. J. Radiol. 2005;78:973- 75. 3. Keevil SF and Krestin GP. EMF directive still poses a risk to MRI research in Europe. Lancet 2010; 376:1124-25. 4. Keevil SF. The European Union EMF Directive and MRI: is a solution in sight at last? Diagnostic Imaging Europe 2012;28(3):8-12. 5. Directive 2013/35/EU of the European Parliament and of the Council. Online at http://new.eur- lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32013L0035&qid=1373881688213&from=EN (accessed 18th August 2014). 6. Keevil SF and Lomas DJ. The European Union Physical Agents (Electromagnetic Fields) Directive: an update for the MRI community. Br. J. Radiol. 2013;86:20130492.
Tuesday 2nd September 2014, 09.30 – 11.00 Biennial Radiotherapy Physics Conference – Dosimetry
Reference dosimetry on TomoTherapy: an addendum to the 1990 UK MV dosimetry code of practice 1Byrne J, 2Thomas SJ, 3Aspradakis MM, 4Chalmers G, 5Duane S, 4Rogers J, 5Thomas RAS, 2Tudor GSJ, 2Twyman N 1Freeman Hospital, Newcastle upon Tyne, UK. 2Addenbrookes Hospital, Cambridge, UK. 3Cantonal Hospital of Lucerne, Switzerland. 4Queen Elizabeth Hospital, Birmingham, UK. 5National Physical Laboratory, Teddington, UK. email: [email protected] IPEM recommends that UK users of MV photon therapy beams follow the IPSM 1990 MV Code of Practice. However, the reference conditions described in the 1990 CoP are not achievable on Tomotherapy equipment, namely a 10x10cm field size. In addition, a number of authors have published work which shows that because of the significant differences in the energy spectrum associated with a flattening filter free (FFF) beam, TPR20/10 cannot be used as a surrogate for the quality index (QI) for determination of ND,W. In March 2014 IPEM published an addendum to the 1990 CoP [1] to allow the NPL MV calibration service to be used to determine an absorbed dose calibration coefficient from the NPL's existing chamber-specific certificate to allow dose to water under reference conditions to be determined for Tomotherapy equipment. This addendum therefore allows Tomotherapy users to replace the use of alanine for reference dosimetry. The methodology and terminology set out in the original 1990 CoP is used as far as possible but for clarity, and consistency with IAEA/AAPM 2008 formalism [2], subscripts and superscripts are used where appropriate. The addendum specifies two options for reference conditions, consistent with the IAEA/AAPM formalism. The first, referred to a machine specific reference condition 10x5cm at 85cm SAD at a depth of 5cm and with additional scattering material extending 5cm outside the field width and downstream of the chamber in a water/equivalent phantom. The second, referred to as a plan class specific reference condition is a region of uniform dose delivered from a plan produced by a treatment planning system as a set of modulated beams, being sufficiently uniform for a dose measurement to be accurately made for the chosen detector. The addendum recommends that the NPL 2611, successor of and equivalent to the 1990 CoP recommended NE 2561 chamber, should be used as the secondary standard (SS) chamber. The recommended method of determining QI in order to use the existing NPL published chamber-specific calibration certificate for determination of ND,W is to measure a TPRTomo ratio for the SS and calculate QI=QITomo to access ND,W from the existing certificate. The method of calculating QITomo from TPRTomo is that published by Palmans [3] by an equivalent square method. General application of the addendum for determination of dose in FFF beams requires the use of a beam quality correction factor to account for the change in response of the chamber in an FFF beam from that in the NPL's conventional flattening filter (cFF) beams. For determination of a calibration coefficient for a field chamber (FC) a side by side intercomparison at a 5x5cm beam at a depth of 5cm is preferred. Determination of dose in static beams is then by direct application of ND,W to the measurement and in modulated beams with an added field dependent correction factor to account for changes in response of the detector when used in modulated beams where significant dose gradients may exist. The addendum recommends the use of unity for this correction for the A1SL chamber currently supplied with Tomotherapy units but recommends that the factor must be determined if other detectors are to be used. 1. Thomas et al. 2014, Reference dosimetry on Tomotherapy: an addendum to the 1990 UK MV dosimetry code of practice, Phys. Med. Biol. 59 (2014) 1339-1352 2. Alfonso et al, 2008, A new formalism for reference dosimetry of small and non-standard fields. Med. Phys. 35 5179 3.Palmans H, 2012, Determination of the beam quality index of high-energy photon beams under nonstandard reference conditions. Med. Phys. 37 2876-2889
A comparison of phantom scatter from flattened and FFF photon beams 1Richmond N, 2 Allen V, 1Daniel J, 1Walker C 1Medical Physics, South Tees NHS Foundation Trust, Middlesbrough, UK. 2The Northern Centre for Cancer Care, Newcastle upon Tyne NHS Foundation Trust, Newcastle upon Tyne, UK. email: [email protected] Background. Flattening Filter Free (FFF) megavoltage photon beams are becoming prevalent on newly installed linear accelerators. These beams have the advantage of a much higher dose rate over conventional flattened beams which may make patient treatment delivery more efficient and less prone to patient motion problems. FFF beams have different dosimetric properties to flattened beams especially in 1 terms of collimator scatter . The aim of this work is to characterise the collimator scatter (Sc) and total scatter (Scp) from three FFF beams of differing quality indices and use the resulting mathematical fits to generate phantom scatter (Sp) data. The similarities and differences between phantom scatter of flattened and FFF beams are described. Methods. Sc and Scp data were measured for 3 flattened and 3 FFF high energy photon beams (Varian 6 and 10MV and Elekta 6MV) in line with published guidance2, 4. These data were fitted to a logarithmic power law function given below where c is the square field size (cm) and α, β, γ and δ, are numerical coefficients.
S or S c-0.5 ln c2 c cp c
The Sc and Scp datasets were subsequently used for the generation of phantom scatter data (Sp = Scp/Sc) for both the flattened and FFF photon beams with nominal energies of 6 and 10MV. 3 Results. The agreement between our experimentally determined flattened beam Sp and published data was within ±1.2% for all 3 beams investigated and all field sizes from 4x4 to 40x40cm2. For the 3 FFF 3 2 beams, Sp was only within 1% of the same flattened beam published data for field sizes between 6x6 cm and 16x16cm2. Outside of this field size range the differences were much greater, reaching -3.1%, -4.4% and -4.4% for the 40x40cm2 fields for the Varian 6MV, 10MV and Elekta 6MV FFF beams respectively. Discussion. The FFF beam Sp increases more slowly with increasing field size than that of the published and measured flattened beam of a similar reference field size quality index, i.e. there is less phantom scatter than found with flattened beams for a given field size. This difference can be explained when the fluence profiles of the flattened and FFF beams are considered. The FFF beam has greatly reduced fluence off axis, especially as field size increases, compared with the flattened beam profile, hence less scatter is generated in the phantom which reaching the central axis. 3 Conclusion. There is scant, if any, published Sp data for FFF beams in a form that could be used as a reference during FFF beam commissioning. More work is required either to map FFF quality index to an equivalent flattened quality index so that existing literature may be used, or to generate tables of FFF Sp reference data. It would be extremely helpful when commissioning FFF beams for the first time to have published dosimetric data in a format similar to that for flattened beams3. Key references. [1] Cashmore J. The characterisation of unflattened photon beams from a 6MV linear accelerator. Phys. Med. Biol. 53 (2008) 1933 – 1946. [2] Dutreix A, et al. Monitor unit calculation for high energy photon beams, Physics for clinical radiotherapy. ESTRO booklet no. 3. Leuven: Garant, 1997. [3] Netherlands Commission on Radiation Dosimetry, NCS Report 12, Determination and use of scatter correction factors of megavoltage photon beams. Measurement and use of collimator and phantom scatter correction factors of arbitrarily shaped fields with a symmetrical collimator setting. (NCS, Delft, 1998). [4] Zhu T C, et al. Report of AAPM therapy physics committee task group 74: In-air output ratio, Sc, for megavoltage photon beams, Med Phys 36(11) (2009) 5261-5290
EPID dosimetry – Dose response characteristics using commercial software: Epigray. Navarro C1, Ricketts K1,2, , Adeyemi A1, Bertha C 1Medical Physics, Royal Berkshire Hospital, UK 2Division of Surgery and Interventional Science, University College London, UK [email protected] Background. Published guidelinesA,F recommend performing in-vivo dosimetry during treatment in radiotherapy. Dosimetric verification can be done using semi-conductor diodes and thermoluminescent dosimeters which allow a point dose measurement limited to surface dose. Such techniques do not provide expected accurate sensitivity to anatomical changes, can attenuate the treatment beam, and are time consuming. Due to the rising complexity of treatment techniques such as Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT), the demand for a more robust technique to measure the dose delivered to the patient has also increasedB. Previous studiesD,E suggest the use of Electronic Portal Imaging Devices (EPIDs) as a potential solution, although most centres limit their use to imaging for patient setupC. We have commissioned and implemented an EPIgray System (DOSIsoft, France) to measure transit dose using the EPID panel and enable treatment verification. The aim of this study was to evaluate the ability of the software and EPID panels for dose and treatment verification. Methods. Each of our EPIDs (iViewGT, Elekta) was calibrated for dose using ion chamber measurements. A range of dosimetric characteristics of the EPID panel were investigated including: linearity, field size effects, percentage depth dose, wedged dose, sensitivity to patient thickness change, inhomogeneity sensitivity and IMRT/VMAT capability. All tests were performed for clinically used photon energies of 6MV and 10MV. The EPIgray reconstructed dose was compared with the treatment planning system (Eclipse, Varian) which used the analytical anisotropic algorithm. Tests were performed on phantoms and 30 patients, the sites tested were: head and neck, breast and abdomen for both conformal and IMR Results. The EPID signal characteristics as a function of dose was measured and showed a maximum deviation of 1%. For all open fields, predicted and calculated dose profiles matched with a maximum deviation of 2–3% for the central axis, off axis higher differences up to 6% were found. Reproducibility was tested over several days and on the same day; the maximum deviation was 1.5 %. Dose reconstruction points placed within lung differed to Eclipse dose by up to 3%. Patient results indicated good correlation between predicted and reconstructed dose. Discussion. For all tested field sizes the correlation was good between predicted and reconstructed dose in the CAX, however off-axis the results may vary up to 6%. The technique is sensitive to detecting changes in patient thickness (5% change in thickness corresponded to 5% change in reconstructed dose). The technique was not found to be sensitive to SSD error. Conclusion. Future tests should include more patient data. The software was found to provide a useful treatment verification tool under the following recommendations: dose reconstruction points selected close to the CAX, avoiding regions of high dose gradients and inhomogeneities. Key references A.DH, National Cancer Action Team National cancer peer review programme, manual for cancer services 2008: radiotherapy measures. 2010. B.Markus A, et al. Guideline For The Verification of IMRT 2008 ESTRO. C.Michael G. Herman, et al. AAPM Task Group 58- Electronic Portal Imaging- 2001 AAPM D.Janett L, et al. Simple Proposal for Dosimetry with an Elekta iViewGTTM Electronic Portal Imaging Device (EPID) Using Commercial Software Modules. Strahlenther Onkol 2011;187:316–21 E.Pascal F, et al. In vivo dose verification from back projection of a transit dose measurement on the central axis of photon beams. Physica Medica (2011) 27, 1-10 F.The Royal College of Radiologists, Society and College of Radiographers, IPEM, National Patient Safety Agency, British Institute of Radiology, Towards Safer Radiotherapy. London, 2008.
Optimizing tissue equivalent bolus production using a 3D printer 1Hoffmans-Holtzer NA, 1Galis J, 2Paalman MI, 1Heukelom S 1Department of Radiotherapy, VU University Medical Center, Netherlands. 2Department of Physics and Medical Technology, VU University Medical Center, Netherlands. email: [email protected] Background. Patient specific tissue equivalent boluses (TEB) can be applied to induce scatter to increase skin dose or to improve correspondence between dose calculation and dose delivery. Since conventional TEB are handcrafted, the quality of conventional TEB construction depends on training and experience of the staff and as well as on bolus construction method and material. The implementation of 3D printing for TEB1 leads to an adapted clinical workflow, which could improve construction consistency and quality of the boluses. Methods. In the conventional TEB construction a patient is scanned with the wax model which is shaped to the patient prior to the planning-CT. Concurrent with the treatment planning process the TEB is generated from the wax model; a negative cast mould is produced in which an in-house prepared mixture is poured of two-component room temperature vulcanizing silicon rubber-like material and plasticizer. After hardening, this yields a TEB with 1.08g/cm3 mass density and ~250HU electron density, which is flexible but preserves shape under mild mechanical stress. In this TEB production process the quality of the TEB mainly depends on the quality of the wax model. To improve the quality, in-house software was developed that uses the planning-CT information for digital modelling. The software converts approved virtual delineated boluses (with density override) from the treatment planning system to a 3D printer format. This enables 3D printing of cast-like negative moulds of delineated boluses. The TEB production from these negative moulds will proceed according to the described pouring process. The first clinical experiences were evaluated. Results. At time of writing the negative mould 3D printing method is applied for 10 selected clinical high- energy photon beam patients. From these cases the three main findings are: (1) digitally shaping of TEBs during treatment planning process leads to optimal bolus size and position, (2) digitally shaping avoids mechanical stress as during wax modelling, leading to better fitting of the TEB and (3) with the increasing experience the workload is reduced, as the wax shaping (in presence of the patient) and melting is more time-consuming than digitally shaping. Discussion. Direct TEB printing instead of negative mould printing would further optimize the TEB production. Direct positive 3D printing of rubber-like material is tested but not yet implemented, as the mass density of 1.12-1.13g/cm3 was found inappropriate for clinical implementation. Nevertheless, much is expected from new upcoming 3D printing materials with more appropriate characteristics. Conclusion. First results using 3D printing for manufacturing TEBs are promising; while direct 3D printing of boluses is being further developed, the negative mould printing method is a suitable alternative, which has optimized the TEB production and is well received by radiation oncologists, physicists, technicians and the patients. Key references. 1. Hoffmans-Holtzer NA, Galis J, Paalman MI, Heukelom S, Radiotherapy and Oncology (2014) Volume 111, Suplement 1, Page 700
Tuesday 2nd September 2014, 11.30 – 13.00 Update Scientific Session (MPE & RWA)
Highlights of the RWA Update Meeting Mayles P, The Clatterbridge Cancer Centre NHS Foundation Trust Email: [email protected] The second IPEM Radioactive Waste Adviser Update meeting was held in Newcastle alongside the Annual RPA update meeting and an MPE update meeting on July 9th. This was opportune timing since those who obtained their RWA certificates under the grandfather arrangements have been given to the end of this year to submit a portfolio for a substantive certificate if they wish to continue beyond the expiration of their current certificate.
Jan Passchier began the meeting with a presentation on Best Available Techniques in the context of Medical Cyclotrons. This was followed by a useful summary of the Transport Regulations from John Hursthouse from the Office for Nuclear Regulation. This proved something of a wakeup call to ensure that proper arrangements are in place for the consignment of radioactive materials including the appointment of a Dangerous Goods Safety Adviser. (The latter also appeared in the RPA update meeting with a warning against getting the same person to be RPA, RWA and DGSA.) Amber Bannon from the Environment Agency gave a talk and a demonstration of using the Initial Radiological Assessment Tool, available from your EA Inspector. An understanding of this is essential to the preparation of the environmental risk assessment associated with an application for an Environmental Permit to dispose of Radioactive Waste. She demonstrated how the default figures contained in the EA spreadsheets could be refined in circumstances where the initial calculation predicts a dose to a member of the public greater than 20µSv/yr. Jennifer Poveda from Nottingham provided a practical example of a risk assessment relating to the effluent from a Nuclear Medicine department. Stephen Dainty from Stoke enlightened us on the hazards associated with radioactive tiles from the Potteries in the context of decommissioning an old hospital. Philip Orr from Belfast considered the waste issues associated with decommissioning a linear accelerator which concluded that the target and flattening filter of a high energy linac should be retained on site for 2 or 3 years. Bill Thomson from Birmingham discussed the issue of the disposal of stress incontinence pads following 131I therapy for thyroxicosis with a strong recommendation that it was not appropriate to refuse treatment to such patients on the basis of the radiation protection issues. The meeting concluded with a presentation from Julie Robinson from Guys and St Thomas’s Hospital about issues for disposal of molecular therapy radionuclides such a 223Ra and the issue of a patient who dies shortly after the administration should be dealt with.
Tuesday 2nd September 2014, 11.30 – 13.00 Biennial Radiotherapy Physics Conference – Planning I
Current Status DH Innovation Fund Hart R, Radiotherapy Services Manager, Assistant General Manager - Specialist Palliative Care, Nottingham University Hospitals NHS Trust, City Campus, Hucknall Road, Nottingham NG5 1PB email: [email protected] Russell Hart will cover the background of the English 2012 Radiotherapy Innovation fund. He will aim to describe the rationale for the fund in terms of achieving the Prime Minister’s personal pledge of improving access to advanced radiotherapy techniques. The talk will also cover the process followed and then review the effect of the fund.
Effect of tracking latency on 4D SABR lung plans Bedford J, Nill S, Fast M, McNair H, Ahmed M, McDonald F The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, UK. email: [email protected] Background. Tumour tracking may be used to follow the respiratory motion of a lung tumour, thereby allowing a reduction in the internal target volume, with consequent reduction in irradiated volume of normal tissue [1]. Normally there is a small latency between the time of determining the tumour position and the time of positioning the multileaf collimator (MLC) leaves [2], which may be overcome by the use of a prediction algorithm. This study investigates the impact of any residual tracking latency on the target coverage and irradiated volume of normal tissues. Methods. Five SABR lung patients were retrospectively considered. Patients were CT scanned in breath hold and VMAT plans were created for each patient, with a prescribed dose of 55 Gy in 5 fractions to 95% of the ITV and with GTV-to-ITV margins of 0 to 5 mm. The VMAT plans used an Agility MLC with 5-mm leaf width (Elekta AB, Stockholm, Sweden), allowing a penumbra margin of 0 mm transaxially and 4 mm superiorly and inferiorly. Tumour motion was then taken to be purely superior-inferior, in the form z = A – 2A sin6 [π t/T], where z was positive towards the head of the patient, the amplitude A was taken to be 10 mm and the time period of motion, T, was taken to be 4s. Tracking motion was taken to be of the form z = A – 2A sin6 [π (t – θ) / T], where the latency θ was varied from 0 ms to 2000 ms in 50 ms intervals. The offset of the beam aperture with respect to the moving GTV was modelled by considering the GTV to be the static breath-hold GTV and the beam aperture to move with respect to the GTV. A probability distribution of beam aperture position with respect to GTV was constructed, and dose distributions, calculated on a 2-mm grid by shifting the VMAT plans to the corresponding position with respect to the GTV, were then summed in the appropriate proportions, giving a 4D dose distribution for each tracking latency. Results. Figure 1 shows the effect of GTV D95 for various tracking latencies. In the absence of an internal target margin, the impact of latency is strongest, but if a small margin is used, the impact is lessened. Lung V13Gy increases from 3.7% to 5.7% as the internal target margin is increased from 0 mm to 5 mm. The irradiated volume of lung is approximately independent of the latency. Figure 1. Effect of tracking latency on GTV D95. A 2% reduction in dose from 55 Gy is indicated by the dotted line. The probability distribution of aperture position for 500 ms latency is shown in the inset. Discussion. Misalignment of the beam aperture and GTV due to residual latency after position prediction obviously reduces the GTV coverage. Some mitigation occurs due to the normal penumbra margin included for dosimetric coverage. The exact reduction in GTV coverage depends on the size and shape of the GTV, the breathing period and the breathing pattern. These results are consistent with those of Sawkey et al. [2]. Conclusion. For the model parameters used, a residual tracking latency of less than 150 ms produces a reduction in GTV D95 of less than 2% and can be neglected. With a 2-mm internal target margin, a residual tracking latency of 450 ms is acceptable. We are grateful to Elekta AB (Stockholm, Sweden) for funding this project and we acknowledge NHS funding to the NIHR Biomedical Research Centre for Cancer. Key references. [1] Davies GA, Clowes P, Bedford JL, Evans PM, Webb S and Poludniowski G. An experimental evaluation of the Agility MLC for motion-compensated VMAT delivery. Phys. Med. Biol. 58: 4643-4657 (2013). [2] Sawkey D, Svatos M and Zankowski C. Evaluation of motion management strategies based on required margins. Phys. Med. Biol. 57: 6347-6369 (2012).
Investigation into the use of custom-generated bi-directional wedged fluence maps for forward planned IMRT breast treatments 1Hand A, 1Williams A 1Radiotherapy Physics, Norfolk & Norwich University Hospitals NHS Foundation Trust, UK email: [email protected] Background. In our department, breast treatments have traditionally been planned using tangential fields with setup angles determined via the Casebow equations1. Until recently, Segmented IMRT was used to reduce hotspots. In 2012, a new sliding window technique was implemented as an alternative to the irregular surface compensation and inverse-planned IMRT methods used by other centres4, allowing more flexibility for modifying the dose distribution and improving coverage. This technique uses ‘wedged fluence maps’, which were created for all standard dynamic wedge angles available on the linacs2, based on the SST information used in the planning system (Eclipse, Varian Medical Systems)3. The required fluence maps are imported into the plan and then edited where necessary to achieve the optimal dose distribution. This is now standard practice in our department and has been used to treat over 750 patients. The aim of this project was to investigate the use of custom-generated wedged fluence maps, creating a greater range of wedge angles and the capability to operate in two directions simultaneously for more flexible planning. Methods. The standard wedged fluence maps currently used in our planning process were imported into Excel and the change in fluence per mm for each wedge angle was analysed. This is not a fixed value but varies with distance from the centre of the field. Second-order polynomial curves were fitted to the data and the coefficients recorded. Further analysis revealed that a third-order polynomial function could be used to determine the values of these coefficients for any wedge angle. Fluence maps for the ‘standard’ wedge angles were generated in Excel using these functions and used to produce a range of plans. Resulting dose distributions were compared to plans generated using the existing wedged fluence maps. Several further plans were made using generated non-standard and bi-directional wedged fluences. Independent MU check and fluence checks were carried out using IMSure (Standard Imaging, Inc) and plan verification was carried out via a ‘virtual 2D array’ comparison5 and portal imaging to confirm satisfactory plan delivery. Results. Plan comparison between ‘standard’ and ‘custom-generated’ wedged fluences showed maximum differences of <0.3Gy over a 40Gy course. IMSure checks gave acceptable results for all plans (<2% dose difference and 100% pass at 3%/1mm for gamma analysis). Portal dosimetry analysis showed 100% pass rate for 3%/3mm global gamma and virtual 2D array results showed >99% pass rates at 3%/3mm local gamma for all plans (100% pass at 4%/4mm) . Discussion. The results show that plans with custom-generated wedges are comparable to plans currently in clinical use. All plans produced gave acceptable QA results. Often, standard plans for chest walls are found to have poor coverage superiorly and hotspots inferiorly, requiring significant fluence editing to produce acceptable distributions. The use of bi-directional wedges will allow improved distributions with minimal editing, reducing planning time and producing smoother leaf motions. Future uses may also include cases where fields are too large for dynamic wedges. Conclusion. Using the method described, customised wedged fluence maps can be generated which produce acceptable clinical breast plans, including non-standard and bi-directional wedges. Key references. 1. Casebow, M P 1984 “Matching of adjacent radiation beams for isocentric radiotherapy” Br. J. Radiol. 57 735 2. Floriano-Pardal, A & Williams, A 2006 “Investigation into a new direct planning IMRT technique in breast patients” Poster Presentation, IPEM Biennial Radiotherapy Meeting 3. Papatheodorou, S, Zefkili S & Rosenwald J-C 1999 “The ‘equivalent wedge’ implementation of the Varian Enhanced Dynamic Wedge into a treatment planning system” Phys. Med. Biol. 44 509 4. Smith, W. et al. 2010 “IMRT for the breast: a comparison of tangential planning techniques” Phys. Med. Biol. 55 1231 5. Williams, A 2012 “IMRT Patient Specific QA – without a linac” IPEM Conference Presentation, IMRT Verification: making the most of it
AutoLock: an automated system for radiotherapy treatment plan quality control 1Dewhurst J M, 1Lowe M, 1Hardy MJ, 1,2Boylan CJ, 1Smith SC, 1Whitehurst P 1Christie Medical Physics & Engineering, The Christie NHS Foundation Trust, Manchester, UK (2Now at Varian Medical Systems, Helsinki, Finland) email: [email protected] Background. Independent checking is an essential component of radiotherapy treatment plan quality control (QC). Many elements of this QC are well suited to automated checking because they are time consuming for a human to perform but can be checked in a straightforward manner and quickly by computational procedures. Other elements are not well suited to automation but can be included in a checklist. Checklists are increasingly being applied in healthcare as a tool for error management, following UK and international guidelines [1-3]. Automated checking and checklists have been successfully implemented in radiotherapy treatment planning [4, 5]. We have developed and clinically implemented an automated system for QC of radiotherapy treatment plans, named AutoLock. AutoLock is designed to augment our checking procedures by automatically checking aspects of treatment plans which are well suited to computational evaluation whilst summarising more subjective aspects in the form of a checklist. It is also intended to improve the efficiency of the treatment planning workflow by reducing the number of plans rejected at the checking stage. Methods. AutoLock is written in Java and integrated into the Pinnacle3 treatment planning system using dynamic Pinnacle scripting (see [4]). Around 30 individual checks are currently implemented and more can be added through the use of an expandable model. Check results can be “Pass”, “Fail” or “For review”. “For review” results occur where the check cannot be fully automated; a summary of such results is automatically added to a checklist for the planner to review. The planner must acknowledge and accept all checklist items before the plan can proceed to the independent checking stage. AutoLock includes checks of prescription, dose calculation parameters, density overrides, beam labelling and MLCs/jaws. Results. AutoLock has been in clinical use since January 2014. The checking rejection rate fell by 36% following the introduction of AutoLock. A similar reduction in rejection rates was seen in [5]. Discussion. By automating some aspects of treatment plan QC, AutoLock can help to reduce errors and improve workflow efficiency. AutoLock provides instant, impersonal feedback to the planner and acts as a filter to condense the large amount of information requiring human assessment into a manageable checklist. AutoLock was introduced at The Christie as part of a broad effort to reduce checking rejection rates; the precise impact of AutoLock requires further investigation. More checks can be added to AutoLock and this will be the focus of future work. Conclusion. We have developed and clinically implemented an automated system for radiotherapy treatment plan QC, named AutoLock. In addition to augmenting independent checking procedures, the use of AutoLock during planning has contributed to a reduction in the checking rejection rate, and thereby improved the efficiency of the treatment planning workflow. References. [1] Towards Safer Radiotherapy (2008), London: RCR [2] World Alliance for Patient Safety (2008), Radiotherapy Risk Profile, World Health Organization [3] Dunscombe P (2012), Front. Oncol. 2:129 [4] Yang D and Moore K (2012), Med. Phys. 39: 1543 [5] Breen S and Zhang B (2010), Radiotherapy and Oncology 97: 579
Validation of dose calculation on CBCT images for adaptive radiotherapy. 1Naisbit M, 1Ward G, 1Wright SL, 1Lindsay R, 1Sykes JR 1Leeds Cancer Centre, St James’s University Hospital, Leeds, UK Email: [email protected] Background: During a patient's radiotherapy treatment, changes to tumour size, external contour and organs at risk can lead to changes in delivered dose, sometimes requiring adaption to their treatment plan [1,3]. Dose calculation on cone-beam CT (CBCT) images acquired during image guided radiotherapy has the potential to improve adaptive RT decision making [2,3,4,5]. This study investigated methods of calculating dose on CBCT images using a pre-release version of the CBCT acquisition software (XVI 5.0, Elekta) which includes an improved HU calibration process. Methods: Three phantoms were investigated to establish an appropriate correction curve to convert CBCT number to electron density (CBCT-ED). CT and CBCT scans were acquired for each phantom and imported into the Monaco 3.3 treatment planning system (Elekta). Regions of interest were analysed to determine a CBCT-ED curve for each phantom (fig 1a). Each CBCT-ED curve was validated by comparing dose calculated for a prostate VMAT FFF plan based on both a CBCT and CT scan of the Virtually Human Male Pelvis (VHMP) phantom (CIRS Inc.). The CBCT-ED curves were further validated using data from four prostate patients, treated with VMAT FFF, all CBCT scanned at treatment with a medium field of view with length 13cm. Deformable image registration was performed to deform the CBCT scan to the planning CT geometry, allowing dose comparison whilst minimising the effect of changes in patient anatomy. Dose calculated on the CT and CBCT studysets was compared using DVH statistics. Results: Significant dose differences were found using the RMI and CATPHAN CBCT-ED curves. This was attributed to shadowing artefacts around high density materials. The CIRS homogeneous phantom provided the optimal CBCT-ED curve as it was possible to scan this phantom with different inserts separately to reduce shadowing artefacts. Validation of the CIRS CBCT-ED curve using patient data showed that the target volume DVH statistics were comparable (the mean [range] difference between CT and CBCT D98%, D2% and D50% parameters for the PTV were 0.7Gy [0.4-1.2Gy], 1.2Gy [1.0-1.4Gy] and 1.0Gy [0.9-1.3Gy] respectively), and the mean difference in dose to the isocentre was 1.8% (SD = 0.5%). It was not possible or meaningful to compare dose statistics for organs at risk as the entire bladder volume is not always included in the CBCT scan and rectal filling can vary significantly. A comparison of the 3D dose distribution showed that the difference in dose between the CT and CBCT plans was within 5% for all patients for regions away from the periphery (fig 1b).
(1a) (1b)
Figure 1 a) CBCT-ED curves for the three phantoms compared to the clinical CT-ED curve; b) the dose difference between CT and CBCT for patients 1-4 using the CIRS homogeneous phantom CBCT-ED curve. Conclusion: Clinically acceptable dose calculation accuracy on CBCT studysets can be achieved using a CBCT-ED curve based on the CIRS phantom. Key References: 1Hu et al: Use of kilovoltage X-ray volume imaging in patient dose calculation for head- and-neck and partial brain radiation therapy Rad. Onc. 2010, 5:29. 2Fotina et al: Feasibility of CBCT-based dose calculation: Comparative analysis of HU adjustment techniques. Rad. Onc. 2012, 104:249-256. 3Ritcher et al: Investigation of the usability of conebeam CT data sets for dose calculation. Rad. Onc. 2008, 3:42. 4Van Zijtveld et al: Correction of conebeam CT values using a planning CT for derivation of the ‘dose of the day’. Rad. Onc. 2007, 85:195-200. 5Yadav et al: Feasibility study on effect and stability of adaptive radiotherapy on kilovoltage cone beam CT. Rad. Onc. 2011, 45:3.
Tuesday 2nd September 2014, 11.30 – 13.00 Author Workshop
Best practice in writing for publication of scientific papers in a peer-reviewed journal: from an editor’s perspective Black R A, Editor-in-Chief, Medical Engineering & Physics Email: [email protected] Research has been defined as “a process of investigation leading to new insights effectively shared” [1] hence writing for publication is an essential part of that process. The work of an academic goes hand-in- hand with communicating the results of research, but it is not simply about getting your work into the public domain: it is also about ensuring that a paper reaches the widest possible audience and is read by them; hence the increasing emphasis placed on bibliometrics as a measure of how effective we are at communicating the results of our research. Arguably, to be successful therefore, one also has to be able to communicate effectively in writing, which is a skill that takes time and practice to develop. Nevertheless, it is surprising how often problems occur.
In this presentation I shall remind authors (and reviewers) of their obligations, which are published in the author guidelines of most journal web sites [2-4]. With knowledge of the review process, and the criteria used to assess the quality of a paper submitted for publication, I believe many of these problems we as journal editors encounter when dealing with submissions might be averted.
Authors are required to make a series of disclosures about the work reported in a manuscript: declaring any conflict of interest, perceived or actual; acknowledging the source(s) of funding; and, for work involving human subjects, prior approval by an institutional review body on matters of ethics. Authors are obligated also to ensure also that any images or original artwork, even those that are generated by the authors themselves, and published in conference proceedings, for example, are not subject to copyright. In such cases permission to reproduce the material should be sought from the copyright owner prior to submission. Again, I refer readers to the author guidelines for details of the procedures that should be followed.
This presentation aims to offer practical advice and guidance on best practice when preparing manuscripts for submission to peer-reviewed journals across a range of disciplines [5-7], and to direct authors and reviewers to the resources freely available on publishers’ web sites. Participants will gain insights into the workings of the publication process, and learn how their research and practice fits into the wider research landscape.
References and bibliography [1] Research excellence framework: second consultation on the assessment and funding of research, HEFCE Research Excellence Framework, September 2009 (www.hefce.ac.uk) [2] Understanding the publishing process, Elsevier Ltd. http://cdn.elsevier.com/assets/pdf_file/0020/131816/Understanding-the-Publishing-Process.pdf [3] Elsevier for reviewers www.elsevier.com/reviewers/home [4] PLOS Medicine Guidelines for Authors/Reviewers: www.plosmedicine.org/static/reviewerGuidelines [5] Earnshaw, J.J. (2012) How to write a clinical paper for publication. Surgery (Oxford), 30(9) 437-441 [6] Whitesides, G. M. (2004) Whitesides' Group: Writing a Paper. Adv. Mater., 16: 1375–1377 [7] Brand, R.A., Huiskes, R. (2001) Structural outline of an archival paper for the Journal of Biomechanics. J. Biomechanics, 34: 1371-1374
Tuesday 2nd September 2014, 14.00 – 15.30 Update Scientific Session – RWA2000
An Update on RWA submissions and assessment. Sutton D G, Department of Medical Physics, Ninewells Hospital, Dundee Email: [email protected] This presentation will briefly outline the reasons why RPA2000 have developed a certification scheme for Radioactive Waste Advisers. It will go on to explain the differences between the approach taken for applicants who have an RPA certificate and those who don’t. The situation with regard to the certification of grandfather rights certificate holders will be discussed in more detail. In particular, we will look at matters such as grandfather certification itself, the trajectory for applications, numbers of expected applicants by work sector and the reason why a cut-off date of January 2015 has been introduced. We will discuss the measures put in place to try and assist applicants to complete their applications. We will consider the Tsunami of applications (or rather its non-appearance), how many RWAs are in place and how many will not be by June 2016. It is likely that large numbers of Grandfather RWAs will not receive their certificate by 30 June 2016 and will cease to be RWA.
Experiences of submitting a RWA portfolio 1Worrall M 1Radiation Physics, NHS Tayside, Ninewells Hospital, Dundee, UK. email: [email protected]
Those of us who Grandparented as Radioactive Waste Advisers need to recertify by June 2016. RPA2000, the body who will be assessing the applications for recertification, have indicated that only applications received by the end of 2014 are guaranteed to be fully assessed before Grandparent rights expire.
With the application process for RWA certification new for everyone involved, it was agreed that after submitting a RWA portfolio for assessment, I would meet with the RPA2000 assessors and discuss my portfolio content and that likely to come from other RWAs in the medical sector.
This left everyone present with a greater familiarity of the evidence likely to be submitted as medical RWAs begin making their applications for recertification. It left me with a greater understanding of what the assessors deem as adequate evidence to meet the competencies.
RPA2000 have asked that I communicate this information to my medical RWA colleagues. With a full four months before the application deadline, it is hoped this information helps those putting together their portfolio and comes in plenty time to help.
Portfolio content and an outline of the likely time commitment in constructing a portfolio will be discussed during the presentation.
Tuesday 2nd September 2014, 14.00 – 15.30 AAG Scientific Session – Big Data I
Radiomics: Decoding the Tumor Phenotype by Non-Invasive Imaging Dekker A, Maastricht University, Maastricht, Netherlands Email: [email protected] Background Human oncologic tissues exhibit strong phenotypic differences, such as intra-tumor heterogeneity or level of spiculation. Due to advances in both acquisition and analysis methods of medical imaging technologies, the extraction of reliable and informative image features to quantify these differences between patients, is currently possible. As this is an emerging field, many of these phenotypic characteristics are not routinely quantified or yet used in clinical decision-making. Radiomics addresses this issue by converting medical images into minable data through the application of data-characterization algorithms. Methods Here, we present an analysis of 440 “radiomic” features quantifying phenotypic differences based on its image intensity, shape and texture, extracted from computed-tomography images of 1019 patients with lung or head and neck cancer. Results We found that a large number of radiomic-features have strong prognostic power, many of which never were identified as significant before. A radiomic-signature capturing intra-tumor heterogeneity, was strongly prognostic in independent datasets of lung and head and neck cancer patients, and associated with underlying gene-expression patterns. Conclusions These data suggest that radiomic-features decode a prognostic phenotype existing in both lung and head and neck cancer and which may generalize to other tumors. This can have a large clinical impact as imaging is routinely used in oncology practice worldwide, providing an unprecedented opportunity to improve decision-support at low cost
Research Database of Oncology Medical Images 1Patel M, 2Young K, 1Halling-Brown M 1Scientific Computing, Royal Surrey County Hospital, Guildford, UK. 2National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford, UK. email: [email protected] Background Radiological imaging is fundamental within the healthcare industry and has become routinely adopted for diagnosis, disease monitoring and treatment planning. Over the past two decades both diagnostic and therapeutic imaging have undergone a rapid growth. The ability to be able to harness this large influx of medical images can provide an essential resource for research and training. Traditionally, the systematic collection of medical images for research from heterogeneous sites has not been commonplace within the NHS and is fraught with challenges including; data acquisition, storage, secure transfer and correct anonymisation. This demand has led us to design and implement a flexible image repository, which prospectively collects images and associated data from multiple sites throughout the UK. The Oncology Medical Image Database (OMI-DB) has been created to provide a centralised, fully annotated dataset for research. One of the most important features is the inclusion of unprocessed images which are not usually routinely saved to PACS. Remotely accessible systems have also been developed to allow expert radiologists to annotate the images with interesting clinical features and provide descriptors of these features. Furthermore, calculated and derived data can be obtained from the images at the time of collection which includes a huge number of image features, properties and characteristics that can be useful for classification, CAD and radiomics applications. Methods The database contains unprocessed and processed images, associated data and expert-determined ground truths. The process of collection, annotation and storage is fully automated and adaptable and has been described extensively elsewhere (1). Currently our efforts have focused on collecting images for cancer cases, in particular mammography. However, the system has been designed to be easily extended to any modality. All images and data are anonymised by our bespoke collection systems in compliance with DICOM supplement 142. Currently, the associated data comprises radiological, clinical and pathological information extracted from the National Breast Screening System (NBSS). However the collection system is flexible enough to allow new data sources. The identification of cases is achieved via an automated process involving the relevant clinical database. Furthermore, a web-enabled, remotely accessible software application MedXViewer (www.medxviewer.com) has been developed which allows radiologists to view cases, annotate clinical features and participate in observer studies. Results At present we have collected 2,623 patient cases, consisting of 34,014 2D images of which 680 are normal cases, 1,836 malignant and 107 benign. These images and systems are being used in multiple on-going studies and have been used in published multi-site observer studies (2,3). Conclusion A valuable database have been developed which holds both processed and unprocessed mammographic images. The provision of unprocessed images enables a multitude of potential research applications. The availability of associated data and expertly determined ground truth along with computational image feature extraction can facilitate other research applications, such as big data analysis. References 1. Patel, M. N., Looney, P. T., Young, K. C., and Halling-Brown, M. D., Proc. SPIE 9039 Medical Imaging (2014) 2. Warren, L. M., Cooke, J., Given-Wilson, R., Wallis, M., Halling-Brown, M, D., Mackenzie, A., Chakraborty, D, P., Bosmans, H., Dance, D, R., Young, K, C. Proc SPIE Medical Imaging (2013) 3. Mackenzie, A et al, “Using image simulation to test the effect of detector type on breast cancer detection,” Proc. SPIE 9037 Medical Imaging (2014)
Big Imaging Data: Implementation of a Research PACS for flexible and secure access to multimodality imaging and radiotherapy data Doran S, Collins D, d’Arcy J, Welsh L, Leach M Institute of Cancer Research, London, UK email: [email protected] Background. Picture Archiving and Communications Systems (PACS) are now ubiquitous components of radiology. For routine applications, they provide a robust, secure and easy-to-use interface to clinical imaging data [1]. However, for research applications, the traditional clinical PACS is insufficiently flexible. Increasingly, structured access to and searching of archives containing large and very heterogeneous datasets is needed (for example, multimodal clinical image data, radiotherapy treatment plans, dose-cubes, DVH’s and dosimetry, histology and genomic profiling). Patient examinations often include both clinical management and academic research components, which have very different drivers in relation to workflow and use of data. Methods. XNAT [2] is a cross-platform, open-source tool from Washington University, St Louis, designed specifically to support imaging research. Its core function is to manage the import, archiving, processing and secure distribution of image and related study data. XNAT has a significant track record and is rapidly gaining traction in the imaging research community, with more than a decade of development already and an NIH programme funded till at least 2017. Since 2008, we have been developing the concept of a Research PACS [1] based on XNAT augmented by locally developed code. Our software is now being contributed back to the main XNAT project as the ICR XNAT DataChooser (featured product at www.marketplace.xnat.org), an application programming interface (API) allowing external tools to interact with XNAT via a customisable data browser enabled within arbitrary end-user workstation applications. Three different XNAT data archives are currently “in production” at the ICR: a system containing anonymised clinical research data, currently containing some 46 projects, including over 20 clinical trials; a secure 50 TB system for patient-identifiable information, which will receive all data generated by our clinical MR unit, currently containing close to 5 million image files; an outward-facing repository for multicentre trial data, accessible securely from anywhere in the world, established in response to CRUK’s agenda of collaboration between the four UK Cancer Imaging Centres. Results. INSIGHT is a trial of the use of multifunctional imaging for defining biological target volumes for radiotherapy of locally advanced head and neck cancers, assessing disease response and predicting loco- regional control in patients undergoing chemoradiotherapy. Our XNAT-based Research PACS is now providing significant time-savings in managing the data. A workflow and standard operating procedure has been devised that: pushes data directly from the scanner to the Research PACS as easily as to the Clinical PACS (eliminating the need for our previous DVD archive and reducing significantly the time needed to select and retrieve research data); makes it easy to anonymise data according to arbitrary project protocols and grant access to a trial- specific subset of authorised users; allows us to add to the study record arbitrary additional data, including regions-of-interest via radiotherapy DICOM objects (RT-STRUCT) and model fits from dynamic-contrast MRI. Discussion and Conclusion. We have successfully developed a state-of-the-art Research PACS to house Big Image Data and integrated it with both hospital and research computer systems. In our presentation, we will present the hardware and open-source software platforms used and discuss the considerations we faced in producing a system compliant with the requirements of the Royal Marsden Hospital. Key references. [1] Doran et al. Radiographics 32, 2135-2150 (2012) [2] Marcus et al. Neuroinformatics, 5(1), 11-33 (2007)
A pilot database to analyse and collaboratively research the UK SABR clinical dataset 1Webster G, 2Baker A, 3Baker C, 4Eaton D, 3Reilly A, 5Hatton M 1Medical Physics, University Hospital Birmingham NHS Foundation Trust, Birmingham, UK. 2Department of Radiotherapy, Clatterbridge Cancer Centre, Bebington, UK. 3Department of Physics, Clatterbridge Cancer Centre, Bebington, UK. 4NCRI Radiotherapy Trials Quality Assurance Groups (RTTQA), Mount Vernon Hospital, Middlesex, UK. 5Department of Oncology, Weston Park Hospital, Sheffield, UK. email: [email protected]
The UK SABR Consortium was established in 2009 with the intention of standardising the national implementation of stereotactic ablative body radiotherapy (SABR) for certain lung cancer patients. Since no phase 3 evidence existed (or exists now) to demonstrate the efficacy of this treatment technique, the intention of the Consortium membership has always been to follow consistent treatment and follow-up protocols and to subsequently share data to produce a uniquely robust clinical dataset for clinical analysis. A survey of the Consortium membership in November 2012 found that approximately 450 lung cancer patients per year were receiving SABR at that time, with this number expected to grow to almost 1200 per year by end 2014 as national and local capacity increases. The Consortium is currently seeking funding to investigate a possible model of collating and then interrogating this UK SABR dataset, which it is hoped will act as a pilot for wider adoption of this collaborative infrastructure in radiotherapy more widely. The key aims of this pilot will be to
1. Establish a uniform framework for data transfer, storage and access that satisfies information governance requirements at multiple institutions 2. Transfer CT, RTDose, RTStruct, RTPlan and clinical outcome data from multiple institutions to a central database 3. Establish and implement quality control procedures to ensure data integrity and safety 4. Design and implement a web interface to access data for analysis
Effect of normal and mixed training databases on the accuracy of a Computer Aided Diagnosis tool 1Taylor J C, 2Barber DC 1Medical Physics, Sheffield Teaching Hospitals NHS Foundation Trust, UK. 2Department of Cardiovascular Science, University of Sheffield, UK. email: [email protected] Background. Computer Aided Diagnosis (CAD) software is usually ‘trained’ with a database of images of known classification or diagnosis. The bigger the database of images the more robust the software is likely to be [1]. However, obtaining such images can be impractical and expensive [4]. Since the advent of Patient Archiving and Communication Systems (PACS) NHS centres have built up large databases of medical images, which could provide an invaluable source of data for algorithm development. As a first step in facilitating easy exploitation of this ‘big data’ resource, without the need to rely on pre-classification, a pilot study was conducted to investigate the effects of using exclusively normal and mixed datasets to train a CAD tool. The CAD tool was based on an image registration algorithm [2] and Principal Component Analysis (PCA) software. The tool derives a set of components and coefficients from intensity data in a training database of ‘normal’ images, which it then uses to filter scans in a method similar to that described by Houston [3]. The residual data is scored according to a global root sum of squares of the intensity values – the ‘index’. In this study the tool was applied exclusively to DMSA scans. Methods. Over 300 adult posterior DMSA images were extracted from the archive at Sheffield Teaching Hospitals and anonymised. Each kidney in each image (624 kidneys in total) was visually scored as either normal or abnormal by one experienced observer. Each image was then registered to a template. The data was split into training sets, to derive principal components, and test sets, to generate index scores and measure algorithm accuracy. At first only normal data were used in the training set (247 kidneys in total). 65 abnormal images were then added (20% of the total) and components recalculated. Both sets of components were used to generate index scores from a separate test database containing 312 kidney images (again, 65 of which were abnormal). After choosing an optimum abnormal / normal cutoff for the index scores overall accuracy was assessed by measuring the proportion of images correctly classified. Results. The overall classification accuracy of the CAD tool was similar for both the exclusively normal training set and the mixed training set – 92.5% and 92% respectively. Discussion. These initial results show that the accuracy of the CAD tool was largely unaffected by the use of a mixed database of training images rather than an exclusively normal dataset. This implies that extensive pre- classification of training data may not be required. A simple ranking mechanism, based on an initial index score, is currently being investigated as a method for automatically removing the most abnormal data from a training set. Conclusion. The study demonstrated that for a CAD tool based on PCA, classification accuracy is relatively unaffected by the addition of small numbers of abnormal images into a ‘normal’ training database. Key references. [1] Armato, SG, et al. 2011. The Lung Image Database Consortium and Image Database Resource Initiative. Med Phys; 38(2). [2] Barber, DC. 1992. Registration of low resolution medical images. Phys. Med Biol; 37(7). [3] Houston, AS, et al. 1994. A method for assessing the significance of abnormalities in HMPAO brain SPECT images. J Nucl Med; 35(2). [4] Van Ginneken, B, et al. 2011. Computer-aided siagnosis: How to Move from the Laboratory to the clinic. Radiology; 161(3)
Tuesday 2nd September 2014, 16.00 – 17.30 Biennial Radiotherapy Physics Conference – Planning III
Analysis of the effect of jaw tracking on OAR doses for Lung Stereotactic Ablative Radiotherapy (SABR) using VMAT 10X flattening filter free (FFF) delivery 1Hall R, 1Andrew Aitken 1Radiotherapy Physics, NHS Greater Glasgow & Clyde, UK. Email: [email protected]
Background. The introduction of new treatment techniques, such as VMAT, has enabled increasing use of dose-escalated fractionation schedules. In particular, SABR is an increasingly popular method for the treatment of non-small cell lung cancer (NSCLC). OAR and normal tissue doses are limited for NSCLC SABR plans based on the recommendations of the ROSEL [1], and other, protocols. However, the use of jaw tracking could potentially further reduce OAR dose contributions from transmission through the MLC. This may be of particular significance for peripherally located lesions when using full arc delivery, where extended field sizes can be used to avoid collision issues. This study was performed to retrospectively compare and, where possible, quantify the effects of jaw tracking on selected OAR doses for VMAT delivery of ten lung SABR datasets.
Methods. The delivery technique utilised an arms down set up with beam direction shell immobilisation. A free breathing 4DCT was used to incorporate motion management with dose calculation being performed on the average intensity projection. In all cases clinical treatment delivery did not incorporate jaw tracking. For each patient, the same objective criteria were used to retrospectively optimise a 10X FFF VMAT plan with jaw tracking activated. All plans were computed using Eclipse v10.0.39, with two arcs of rotation and a prescribed dose of 55Gy in 5 fractions following the ROSEL protocol. In addition to the requirements of ROSEL, a local contra-lateral lung planning constraint (V5Gy≤1%) was also applied. A type B algorithm (AAA 10.0.28) was used throughout. Clinical constraint compliance was recorded to allow comparison between plans.
Results. No statistically significant difference was observed between plans with and without jaw tracking. T- test P values for OAR dose comparisons range from 0.015-1.0. However, the only comparison showing statistical significance (P=0.015) measured a difference of <0.1% in dose.
Discussion. These T-test results suggest that the use of jaw tracking does not result in a significant difference in OAR doses, which in turn suggests that the introduction of jaw tracking to SABR lung plans has a minimal effect. As such it is unlikely that jaw tracking would be used with the aim of reducing OAR doses. However, the reduction of leakage through the MLC may increase confidence in beam modelling accuracy and could be seen as an additional safety measure, reducing the effect of any large errors in MLC leaf positioning.
Conclusion. These results suggest that any OAR dose reduction achieved using jaw tracking may be at the limit of the TPS dose calculation accuracy for this patient cohort. As such, jaw tracking may reduce OAR doses, but this has been difficult to quantify for the case studies selected and requires further verification.
References 1. Coen C.W. Hurkmans, et al (2009) Recommendations for implementing stereotactic radiotherapy in peripheral stage IA non-small cell lung cancer: report from the Quality Assurance Working Party of the randomised phase III ROSEL study, Radiation Oncology, 4 (1).
VMAT Planning study for Upper Oesophageal Cancer Skikiewicz M1, S Thomson1, S Smith1, V MacLaren2 1Radiotherapy Physics, NHS Greater Glasgow & Clyde. 2Beatson West of Scotland Caner Centre, NHS Greater Glasgow & Clyde. email: [email protected] Background. Achieving target conformality and organ at risk sparing with standard 3D Conformal Radiotherapy (3D CRT) can present a significant challenge when treating upper oesophageal cancer due to proximity to spinal cord. Volumetric Modulated Arc Therapy (VMAT) using the Varian RapidArc™ technique may offer a better solution in this particular treatment site. This retrospective study aims to compare treatment plans generated by 3D CRT and VMAT for upper oesophageal cancer cases. Differences will be assessed in terms of target Conformity Index (CI) and Heterogeneity Index (HI), dose volume histogram parameters for OARs and overall plan quality.
Methods. Seventeen cases with locally advanced cancer of the cervical oesophagus were selected who had previously received conventional radiotherapy treatments at the BWoSCC. Each patient was replanned using VMAT with optimisation objectives set to achieve target coverage of 95-107%, whole lung V20Gy less than 20% and max spinal cord dose less than 4500cGy. DVHs were calculated for the PTV, whole lung and spinal cord. Lung V20Gy and max spinal cord doses were evaluated for each plan along with PTV coverage (PTV95%, PTVmax, PTVmin and PTVmean), conformality and heterogeneity index.
Results. VMAT target volume coverage, assessed using CI, appears to be superior over 3D CRT coverage with the values of 0.9 and 0.6 for both techniques respectively; (p<0.005). The mean dose to the PTV calculated using VMAT was also found to be higher (102.3%) than for conventionally calculated plans (99.5%); (p<0.005). The HI shows more homogenous dose distribution for VMAT plans when compared against conventional planning. No statistically significant difference was detected (p=0.413) when comparing whole lung V20Gy. Max spinal cord dose was reduced by 25% (p<0.005) with VMAT relative to 3D CRT.
Conclusion. The plans were compared in terms of PTV coverage, conformality and normal tissue sparing. Results indicate that VMAT technique demonstrates improved target conformality and a reduction in maximum dose to spinal cord in upper oesophageal tumours. VMAT is now available for all upper oesophageal patients in our clinic.
Investigating the use of Partial Arc VMAT for Head and Neck Radiotherapy treatments to reduce dose to contra-lateral parotid gland Moran A M; McWilliam, A Radiotherapy Physics, The Christie NHS Foundation Trust Email: [email protected] Background Patients receiving radiotherapy to the head and neck region commonly experience side effects due to the irradiation of the parotid glands. Due to its position, the parotid gland often is situated proximally or within the treatment volume; thus a part of the organ is likely to receive the prescription dose. Numerous studies, such as the quantic papers and PARSPORT trial, have been carried out investigating the effect of irradiation on the parotid gland. It has been found that limiting the mean dose to one parotid gland to less than 20Gy or limiting the mean dose to both parotid glands to below 26Gy can show improvement to the patient outcomes. A simple method to ensure this for patients with uni-lateral disease is to avoid entrance dose through the contra-lateral parotid gland. With the increase in the number of patients receiving VMAT treatments, it was desirable to commission a new technique for unilateral patients using partial arc VMAT. Method Currently, patients with uni-lateral disease are not differentiated in terms of treatment technique to those with bi-lateral disease at The Christie. A partial arc solution was produced using SmartArc optimisation in Pinnacle3, so as to avoid entrance dose through the contra-lateral parotid gland. A parallel planning study was performed, using a patient sample of 15 patients and producing clinically acceptable treatment plans using IMRT, full arc and partial arc VMAT. This planning comparison compared PTV coverage and organ at risk doses. Comparisons were made using DVH dose statistics as well as the conformity index and the Dice comparison coefficient for PTV coverage and doses to organs at risk. Concerns regarding the technique included the contribution of increased exit dose affecting the dose to the oral cavity and loss of conformity, due to the reduction of angle through which treatment is delivered. Comparison studies were performed to assess the optimum arc length and optimisation parameter values. Results It was found that equal coverage could be achieved using a partial arc in comparison to IMRT and full arc VMAT. The doses to the contra-lateral parotid glands, spinal cord and brain stem can be reduced using the partial arc solution. The dose to the contra-lateral parotid gland was reduced to between 10-20% of the clinical planned values. It was found that the PTV dose statistics were not significantly affected, with conformity indices remaining within 2% of the original planned values. Conclusion Partial Arc VMAT can be used effectively to minimise the dose to the contra-lateral parotid gland while maintaining suitable dose coverage to the target volumes and minimising loss of conformity, in particular of the intermediate doses. References Deasy J, Moiseenko V, Marks L, Chao C, Nam J, Eisbruch A; Radiotherapy Dose Volume effects on Salivary gland function (QUANTEC organ specific paper); International Journal of Radiation Oncology, Biology and Physics; Vol 76:3; pS58-S63; 2010 Eisbruch A, Kim H, Terrell J, Marsh L, Dawson L, Ship J; Xerostomia and its predictors following parotid- sparing irradiation of head and neck cancer; International Journal of Radiation Oncology, Biology and Physics; Vol 50:3; p 695-704; 2001 Nutting C, Morden J, Harrington K, Urbano T, Bhide S, Clark C, Miles E, Miah A, Newbold K, Tanay M, Adab F, Jefferies S, Scrase C, Yap B, A’Hern R, Sydenham, Emsom M, Hall E; Parotid sparing intensity modulated cersus conventional radiotherapy in head and neck cancer (PARSPORT): a phase 3 multicentre randomised controlled trial; Lancet Oncology; Vol 12; p127-136; 2011
Comparison of brain RapidArc plans, planned for a Varian TrueBeam STx and a Clinac. 1 1 2 2 Small A , Suzanne Smith , Allan James , Aoife Williamson 1Radiotherapy Physics, Department of Clinical Physics & Bioengineering, NHS Greater Glasgow & Clyde; 2Beatson West of Scotland Cancer Centre, NHS Greater Glasgow & Clyde email: [email protected]
Background: The Varian TrueBeam STx is a state-of-the-art linear accelerator with a high definition (HD) MLC and is traditionally used for stereotactic treatments, as the MLC affords greater conformality to the tumour and enables doses to the organs at risk (OAR) to be minimised.
Methods: This study compares the treatment planning of brain tumours, delivered using either the Varian TrueBeam STx or a Varian Clinac with a standard Millennium 120 leaf MLC. Twenty patients had RapidArc plans prepared using both MLC types and this allowed the benefits of the high definition MLC on the STx to be assessed. Several parameters were studied, including conformity and homogeneity index, the total number of monitor units, and the mean doses achieved by the PTV and several OARs (the brain, brainstem, optic chiasm and left optic nerve).
Results and conclusion: For the millennium MLC, the mean value of the PTV 95% conformity index is 1.04 with a standard deviation (SD) of 0.03, compared to a value of 1.02 with a SD of 0.02 for the HD MLC. The mean homogeneity index for the millennium MLC is 1.14 with a SD of 0.02 compared to an HD MLC value of 1.12 with an SD of 0.02. This would suggest that the HD MLC is more conformal and gives a more homogeneous distribution than the millennium MLC and is an improvement for standard/non stereotactic treatments.
The mean dose to the organs at risk was also found to be consistently lower with the HD MLC. The mean brain-PTV dose was on average 4% lower with the HD MLC, and the mean brainstem was on average 7% lower. This indicates that the HD MLC also give significant organ sparing.
Investigation of a standard constraint set for VMAT Planning in Prostate Cancer Keiller D Radiotherapy Physics, Beatson Oncology Centre, Glasgow, UK Email: [email protected]
Background. Most patients undergoing external beam radiotherapy for early stage prostate cancer at the Beatson West of Scotland Cancer centre are treated using VMAT to deliver 74Gy in 37 fractions using either one or two 120° arcs. Plans are produced using the Varian Eclipse 10.0 planning system, with optimisation performed using the Progressive Resolution Optimiser version 10.0.28. Plans are generally produced using a standard constraint set. However, in a significant minority of cases the optimisation objectives are modified by the planner in order to meet dose constraints. This work aimed to investigate whether alteration of optimisation objectives was required, or whether the dose constraints could be achieved by re-scaling of monitor units. Methods. A retrospective planning study of patients treated using RapidArc on a Truebeam STx linear accelerator (Varian Medical Systems) with HD MLC was performed. These patients all have two clinical plans: the primary plan and a backup plan for a Varian Clinac IX linear accelerator with Millennium 120 MLC. This allowed additional comparison of the two MLC’s for meeting the prescribed dose constraints Plans for 80 patients were examined, and in 35 cases it was found that the original planner had modified the optimisation objectives. These were re-planned to determine whether it was possible to meet the DVH constraints using the standard constraints and appropriate renormalisation. The number of monitor units required, and the bladder, rectum and prostate volumes were recorded to determine if there was any correlation between these parameters and the probability of a plan failing to meet the DVH constraints. Results. In 16 cases, it was possible to rescale the monitor units in order to pass the DVH constraints, suggesting that the standard constraint set produces clinically acceptable plans in over 75% of cases. The 19 cases where optimisation objectives needed modification in order to meet the dose constraints were compared with the remaining 61 cases. These had a significantly lower bladder volume (mean 133cm3 compared with 226cm3, p=0.0004) but showed no statistically significant difference in prostate or rectum volumes. There was no significant difference in the monitor units required for the HD MLC compared with the Millennium MLC. Discussion These results suggest that standard constraint libraries work well for prostate RapidArc, and require no modification beyond monitor unit rescaling in over 75% of cases. There is also no significant difference between the HD MLC and the Millennium 120 MLC in terms of achieving DVH constraints or number of monitor units required for prostate RapidArc planning. However, further work needs to be done to investigate whether the standard constraint set could be improved in order to meet the dose constraints for patients with small bladders. Conclusion. Standard constraint sets achieve prostate RapidArc plans which meet the required DVH constraints without modification in over 75% of cases. This validates the current approach used clinically at the Beatson Oncology centre.
Skin margins for RapidArc optimisation: How much is enough? 1Tyler J M, 1Poxon J, 1MacDougall ND 1Radiotherapy Physics, Barts Health NHS Trust, London, UK. email: [email protected] Background: The optimisation pitfalls of inverse planned treatments, where the PTV approaches the body contour are widely known. A popular technique employed to avoid overdose in the build-up region is to modify the optimisation volume by subtracting a margin from the skin surface. Optimisation Margins (OM) between 3 and 5mm are reported for IMRT1, 2, 3, 4, but it is unclear whether these margins translate safely to RapidArc. Aim: Find the OM that best covers the PTV and analyse the OMs for resilience to setup error. Test the TPS surface dose calculation with phantom measurements. Model the effect of varying OMs, with setup uncertainty, on clinical plans. Methods: RapidArc planning was carried out using Eclipse TPS (AAA v11.0.31). OMs were varied from 0 to 5mm, in 1mm increments. 1. Phantom: TLD measurements were taken at the surface of a semi-cylindrical WT1 phantom for varying OMs. Isocentre shifts from 2 to 5mm were made to model the effect of setup uncertainty. 2. Clinical: H&N plans were optimised with varying OMs and compared with and without isocentre shifts. Results and Discussion. 1. Phantom: Surface dose measurements with TLD agreed with TPS calculated doses. Reducing the OM to 2mm improved PTV coverage, but increased volumes of dose > 105% and exceeded the 107% maximum (figure 1). Decreasing the OM further decreased the PTV coverage, increased the maximum dose and diminished dose fall-off around the PTV. Isocentre shifts lead to significant increases in the maximum dose for PTVs with less than a 2mm OM. 2. Clinical: Clinical plans optimised with OM of 2mm and 3mm demonstrated improved PTV coverage without significant increase in volumes of dose greater than 105% compared to 5mm OM. However isocentre shifts produced high maximum doses particularly for more complex plans demonstrating the decreasing robustness to setup uncertainty with decreasing OM. V95% V105% 89 25
88 no shift 20 no shift 87
86 15 85 2mm shift 2mm shift 10
84
Volume (%) Volume (%) 83 5 5mm shift 5mm shift 82
81 0 0 1 2 3 4 5 0 1 2 3 4 5 Skin margin (mm) Skin margin (mm) Figure 1: Effect of skin margin (OM) on volume of PTV covered by 95% isodose and hotspots greater than 105%. Conclusion: This study shows that skin margins for RapidArc optimisation may be reduced to 3mm to improve PTV coverage; however resilience to setup uncertainty should be tested. Key references: 1. Court LE and Tishler RB. Experimental evaluation of the impact of different head-and-neck intensity modulation radiation therapy planning techniques on doses to the skin and shallow targets. International Journal of Radiation Oncology Biology Physics. 2007; 69(2):607-613. 2. Lee N et al. Skin toxicity due to intensity-modulated radiotherapy for head-and-neck carcinoma. International Journal of Radiation Oncology Biology Physics. 2002; 53(3):630-637. 3. Ramsey CR, Seibert RM, Robison B and Mitchell M. Helical tomotherapy superficial dose measurements. Medical Physics. 2007, 34(8):3286-93. 4. Shiau AC et al. Dosimetric verification of surface and superficial doses for head and neck IMRT with different PTV shrinkage margins. Medical Physics. 2011, 38(3):1435-1443.
Tuesday 2nd September 2014, 16.00 – 17.30 AAG Scientific Session – Big Data II
TheHiveDB image data management and analysis framework 1,2Muehlboeck J-S, 1,2,3Westman E, 1,2 Simmons A 1Department of Neuroimaging, Institute of Psychiatry, King’s College London, UK 2NIHR Biomedical Research Centre and Biomedical Research Unit for Dementia at South London and Maudsley NHS Foundation Trust and Institute of Psychiatry, King’s College London, UK 3Karolinska Institute, Stockholm, Sweden email: [email protected]
The Hive database system (theHiveDB) is a web-based brain image management framework for cross- sectional and longitudinal single and multi-centre studies of up to tens of thousands of subjects. TheHiveDB has been designed to manage imaging projects, individuals (study participants), scalar data and associated file assets with a focus on data aggregation across modalities (eg brain imaging, clinical and genetic data). In addition to meta data and scalar data management it offers decentralised structured storage across networked computers.
The system supports a rich set of common tasks from image archival and format conversion to established processing pipelines, such as Freesurfer for extraction of scalar measures from magnetic resonance images (MRI). This is made possible by the system's activity and resource management component, which is capable of distributing processing across local computing resources and the cloud. Job submission and data transfers are automated using the SSH-2 protocol. All file assets managed by theHiveDB are identified by means of unique identifiers. Checksum information about all files is stored in the database to warrant both file integrity and authenticity.
Scalar data (variables) are associated with individuals, individuals at timepoints, or may be derived from assets or for example, activity output. Query functionality is delivered without the need to modify the database schema, as the data query module is based on entity-attribute-value (EAV) modelling. Queryable parameters are described as variables (with exportable data dictionary) and grouped into variable collections (e.g. questionnaires). An interactive query composition interface lets the user combine data across all modalities and download tabular data.
The system provides a framework for effective collaborations and resource sharing. It facilitates access to data at all levels, by providing pertinent meta information about image acquisitions, allowing the extraction of individual image series in various formats from DICOM studies and offering direct file download and transfer to workstations for source data and processed output.
The Effect of Big Data on National Dose Surveys Edyvean S1, McDonagh ET2, Wilkins H3, Dunn MA4, Iball GR5 1 Public Health England, CRCE, Chilton, UK. Email: [email protected] 2 Joint Department of Physics, The Royal Marsden, London. 3 Medical Physics Department, Royal Devon and Exeter Hospital 4 Medical Physics and Clinical Engineering, Nottingham University Hospitals NHS Trust 5 Medical Physics & Engineering, Leeds Teaching Hospitals NHS Trust Background National dose surveys in radiology in the UK have been carried out for over twenty years by Public Health England CRCE and its predecessor bodies[4,5,9,10]. They were initiated at a time when contributing institutions were requested to provide limited dose descriptor values for just 10 average-sized patients per exam, usually on paper forms. In recent years the use of digital radiological imaging techniques has become more prevalent and, with new standards for recording radiation dose-related metrics[2,7] such as the Radiation Dose Structured Report (RDSR), alongside a range of new commercial, open source and in- house dose management software solutions, the routine recording of comprehensive information about every single radiation exposure has become reality[3]. For a single exam this can contain several hundred separate items of information, and a single institution might perform a hundred thousand studies each year. The existing software can help to analyse this data for an individual patient, procedure type, or imaging system for local optimisation; the challenge is to see how this very large, rich and distributed data source can best be utilised to create the national radiology dose surveys of the future, in line with IAEA/WHO calls for action[6]. The American College of Radiology has led the way with its Dose Index Registry (DIR)[1], with de-identified RDSRs being sent by participating institutions to a central registry for processing. Methods A number of initiatives are underway that seek to address potential national uses of these data. These include consultation with users of different dose monitoring systems with a view to establishing a common data set that could be shared. Areas of discussion include format, terminology and granularity of the data, what is currently available from different systems and what is necessary to enable useful analysis, including combining with other data sources where desirable. Information governance will be considered including the patient confidentiality, media interest and reputation issues. Discussion One of the major challenges in the age of Big Data is the ability to make sense of the copious data available. On a local level it is possible using the available software and local knowledge to sort similar exams with different names to improve datasets and compare procedures at an intra-modality and inter- modality level. At a national level this is not possible without using common coding systems – for the DIR participating institutions are required to map their procedure codes to the RadLex Playbook ID. In England the National Interim Clinical Imaging Procedure (NICIP) codeset is used for contributing data to the UK Diagnostic Imaging Dataset[8], and is therefore widely available as the requested procedure code in the dose reports. Standardisation of procedure terminology will greatly facilitate a semi-automated system of analysing RDSRs sent to a central location, although the NICIP code standardises information about what was requested, not the indication or what was actually done. Historically UK dose surveys have been carried out at intervals of several years. Continuous, automated dose reporting could provide opportunities for more timely analysis and estimate of population doses. Conclusion ‘Big Data’ techniques offer considerable potential to add value to local dose surveys with comprehensive information merged with patient size, protocol, equipment and user information. At a national level these data are much richer than ever before and can provide a new and comprehensive dataset for medical physics experts and other imaging professionals to optimise radiological imaging and patient outcomes. Key references 1. American College of Radiology. Dose Index Registry. [26.4.14]; Available from: http://www.acr.org/Quality-Safety/National-Radiology-Data-Registry/Dose-Index-Registry. 2. Digital Imaging and Communications in Medicine. Strategic Document. 2014; Available from: http://medical.nema.org/dicom/geninfo/Strategy.pdf. 3. Fornell D. Recording and Managing Radiation Dose: An introduction to medical imaging radiation dose recording software. [2104]; Available from: http://www.dicardiology.com/article/recording-and-managing- radiation-dose. 4. Hart D, Hillier MC and Shrimpton PC. Doses to Patients from Radiographic and Fluoroscopic X-ray Imaging Procedures in the UK - 2010 Review. Chilton: Health Protection Agency, 2012. HPA-CRCE-034. 5. Hart D, Wall BF, Hillier MC and Shrimpton PC. Frequency and collective dose for medical and dental X-ray examinations in the UK, 2008. Chilton, Didcot: Health Protection Agency; 2010. HPA-CRCE-012. 6. IAEA/WHO. Bonn Call for Action. 2013; Available from: https://rpop.iaea.org/RPOP/RPoP/Content/Documents/Whitepapers/conference/bonn-call-for-action- statement.pdf. 7. Integrating the Healthcare Enterprise (IHE). Radiation Exposure Monitoring. [26 April 2014]; Available from: http://wiki.ihe.net/index.php?title=Radiation_Exposure_Monitoring. 8. NHS England / Health & Social Care Information Centre (HSCIC). Diagnostic Imaging Dataset - 2013 Technical Report. 31 October 2013. 9. Shrimpton PC, Hillier MC, Meeson S & Golding SJ.. Doses from Computed Tomography (CT) Examinations in the UK – 2011 Review. Public Health England, 2014: In preparation. 10. Shrimpton PC, Wall BF, Jones DG, Fisher ES, Hillier MC, Kendall GM & Harrison RM. A National Survey of Doses to Patients Undergoing a Selection of Routine X-ray Examinations in English Hospitals. Chilton: National Radiological Protection Board, 1986. NRPB-R200.
The potential impact of datamining and rapid learning in radiotherapy: a lung cancer survival decision support system in routine clinical practice 1Thwaites D I, 2Dekker A, 3Holloway L, 3Vinod S, 3Delaney G, 3Goozee G, 4Bailey M, 4Miller A 1Institute of Medical Physics, School of Physics, University of Sydney, Australia. 2Radiation Oncology, Maastricht University Medical Centre, Maastricht, The Netherlands. 3Radiation Oncology, Liverpool Cancer Therapy Centre, Liverpool (Sydney), NSW, Australia. 4Radiation Oncology, Illawarra Cancer Care Centre, Wollongong, NSW, Ausralia email: [email protected] Background. Large amounts of data are collected on radiotherapy (RT) patients, relating to the patients themselves, their disease, their treatment and outcomes. This dataset holds the potential to provide clinical evidence, adding to clinical trial evidence. A collaborative project has been initiated between NSW RT centres and MAASTRO, co-ordinated by the Institute of Medical Physics, Sydney University, with the aim of evaluating the feasibility and impact of datamining of routine clinical RT data and the use of rapid learning tools in RT in NSW centres. The initial objective is to validate and implement MAASTRO-developed decision support systems (DSSs) for routine practice in Australian cancer centres and estimate their effect on decisions for future patient treatment. The initial approach uses the MAASTRO model as baseline and validates it using local data. The wider approach is to drive the models using more and more data (more centres) towards a more solidly-based decision tool. The philosophy is to transport the model to the data, rather than the data out of the centre, thereby protecting data privacy and overcoming administrative and legal concerns. The initial pilot was for non-small cell lung cancer (NSCLC) patients in Liverpool Hospital’s Cancer Centre (LHCC). Method. An open-source rapid learning system was installed at LHCC. From local data sources, various parameters were extracted for all lung cancer patients, without quality review: histology, RT dose, gender, age, ECOG status, lung function (FEV1), lymph node status, tumour volume and survival. Missing data were imputed using Bayesian methods. The DSS was applied to predict two-year overall survival in stage I- IIIB NSCLC patients treated with curative (>45Gy) or palliative RT. Results. Of the 3919 lung cancer patient datasets identified, 225 were eligible for inclusion in the curative and 238 in the palliative cohort. Exclusions were due to ineligible histology or stage or missing dose, tumour volume or survival data. The DSS successfully predicted a good prognosis group in the curative cohort with a significantly higher survival than a medium/poor prognosis group (2-year survival 69% vs. 27/30%, p<0.001). No survival difference was found for palliatively treated patients (2-year survival for good/medium/poor prognosis group: 18%/16%/16%). Stage was less discriminatory in identifying prognostic groups (2-year overall survival 47% for Stage I-II vs. 36% for Stage IIIA-IIIB, p=0.061) with most good prognosis patients having higher stage disease. In the good prognosis group two-year overall survival was 65% in curatively and 18% in palliatively treated patients. Discussion. The rapid learning system was feasible to deploy in a routine clinical environment, despite the apparently limited proportion of patients for whom complete information was available. However, this does emphasise the importance of quality and completeness of data collection and storage for each patient. The application of these methods to existing data resulted in the identification of a predicted good prognosis group of patients that has been treated palliatively (based on stage information). Hence if used prospectively the DSS has the potential to aid and change clinical decisions and improve patient outcomes. The intention is to test this in a future study. Conclusion. A rapid learning system can be deployed in a clinical environment, with the quality of routinely collected clinical data (without specific quality review) sufficient to validate a DSS. Using patient and tumour information, the DSS is able to identify prognostic groups, with the potential to change clinical decisions based on this new information. The approach is extendable to other treatment sites (eg head-and-neck), to an increasing number of treatment centres as the collaborative group grows and also to prospective testing of the modelling predictions. As more information and parameters are involved, these methods can also potentially inform decisions between treatment technologies and aid progress towards a more ‘personalised medicine’ approach.
Data science at scale in medical imaging Robertson D, Professor and Head of School of Informatics, University of Edinburgh, Edinburgh, UK. Email: [email protected]
We are accumulating very large repositories of medical imaging data but there remains a gulf between the potential availability of data and the analytics we might wish to apply to it. Bridging this gulf isn't straightforward. We must develop architectures for curating and sharing data; relate these to experimental workflows and automated analyses at scale; and across all of this we must ensure that data ownership and the right to privacy is respected.
Building this sort of system is an interdisciplinary challenge that requires collaboration across healthcare, medicine, systems engineering, data management and data analytics. This presentation will summarise the overall challenge; highlight where inroads are being made into it and the situation in the broader canvas of data intensive healthcare.
POSTERS
1. A software suite for image registration in radiotherapy 1Al Sa’d M, , 1Hayes M, 2Jena R 1Cavendish Laboratory, University of Cambridge, UK. 2Department of Oncology, University of Cambridge, UK. email: [email protected] Background. Image registration forms a crucial part of radiotherapy process [1]; for improvement of target definition, volumetric propagation and motion tracking, guided treatment delivery, and dose accumulation. Due to the variety of application scenarios in radiotherapy, choosing an appropriate image registration algorithm depends on a number of factors such as image modalities, and required accuracy and processing speed. There is generally no a priori best algorithm to all image registration problems [5]; a number of algorithms can be tried to find the one best suited. An evaluation of various algorithms is not a trivial task. There are a number of software solutions that offer comparison of different registration algorithms, such as Plastimatch [3] and MITK [2]. These tools, however, are either non-interactive script-based or lack for support to the radiotherapy applications. We present here an open-source, multi-platform software solution that offers a user-friendly interface to validate accuracy and efficiency of various volumetric image registration algorithms in radiotherapy context. Methods. The software developed using a development stack of C++/Qt/ITK/VTK. Qt used for GUI (graphical user interface) development. ITK toolkit [4] used for image processing and registration, and VTK toolkit used for visualisation. The GPU-based implementation from Plastimatch software was used for fast image registration. Results. The software has a visual and interactive design (fig. 1), which enables the user to select the best possible combination of algorithms and their parameters in order to meet requirements for a specific image registration task. The suite offers a wide-ranging catalogue of rigid, affine and deformable image registration algorithms via a user-friendly sequence of options that lead the user through a series of well-defined steps. Radiotherapy structure sets and dose volumes can be imported and displayed. Several simulated and clinical examples have been investigated using the software. Discussion. Providing an intuitive user-interface, the software can be used by clinicians to compare image registration algorithms within the radiotherapy setting. This can be employed to validate results obtained from treatment planning systems or process specific cases that are not already supported by these systems. Scientists and developers can use this software to prototype a combination of image registration algorithms and their settings for particular cases. Conclusion. We presented here a software suite to assess the accuracy and speed of image registration for radiotherapy applications. The software offers a streamlined solution to simplify the evaluation task and select the algorithm best suited for a specific case under study. Key references. 1. Kessler, M.L., Image registration and data fusion in radiation therapy. British Journal of Radiology, 2006. 79(1): p. S99-S108. 2. Neher, P.F., et al. MITK global tractography. 2012. 3. Shackleford, J.A., et al., On developing B-spline registration algorithms for multi-core processors. Physics in Medicine and Biology, 2010. 55(21): p. 6329. 4. Yoo, T.S., Insight Into Images, 2004. Taylor & Francis. 5. Zitova, B., et al., Image registration methods: a survey. Image and vision computing, 2003. 21(11): p. 977-1000.
2. A framework for secure, cloud-based medical image processing 1Al Sa’d M, 1Hayes M, 2Jena R 1Cavendish Laboratory, University of Cambridge, UK. 2Department of Oncology, University of Cambridge, UK. email: [email protected] Background. Analysis of significant volumes of medical images is nowadays an essential part of clinical routine. This requires cutting-edge hardware capabilities, which means increased costs on the healthcare system. Cloud-based computing is a remote and cost-effective approach offering enormous computational resources on-demand. Cloud computing has been used for various medical applications, including hosting medical records [5], volume rendering [2], medical bioinformatics [4] and radiotherapy Monte Carlo simulation [3]. Having computational resources external to the healthcare network also raises security and privacy concerns [1]. Here we describe a general framework for a secure and asynchronous medical image processing service in the Cloud. Methods. The framework encompasses a cloud service that can be accessed by multiple healthcare centres (fig. 1). Client machines provide clinical users with a user interface to request image analysis tasks. Requests are dispatched to an on-site middleware server (MWS) specifying the image datasets to be processed from PACS (Picture Archiving and Communication System). The MWS creates a database record containing: a UUID (Universal Unique Identifier) for the request, requesting user’s details, processing status and information identifying the image dataset in PACS. The MWS then fetches and anonymises relevant images from PACS and then invokes the web-service from the provider, passing invoker details, request UUID, analysis type and anonymised images. At the service provider side, the load balancer distributes workloads across cloud servers. An allocated server starts a processing job according to the analysis type requested by the invoker MWS. The server sends progress updates, and processing results once processing is finished, to the invoker MWS. Having the request UUID attached to messages from cloud servers, the MWS can identify and inform the requesting user on-site via email, for instance. Results. We have successfully implemented a web-service, hosted by Amazon Web Services, as a proof- of-principle for the framework presented here. The service computes statistical analysis for radiotherapy dose distribution per anatomical structures. The result is displayed to the user at the client machine. Image registration and segmentation tools will also be hosted in the Cloud. Discussion. The platform agnostic nature of the cloud makes it preferable for medical software providers to avoid costs associated with the deployment and maintenance of additional hardware and software requirements. For an added security measure, a mutual encryption standard can be employed to exchange the data between the cloud and healthcare centres. A private cloud operated exclusively for the healthcare system is another choice to consider for maximum security. Conclusion. Scalability of resources and on-demand availability of the cloud-based computing presents an interesting opportunity for medical image processing. We presented a framework to utilise cloud-computing opportunities with enhanced security and privacy protection. Key references. 1. Ming, L., et al., Scalable and Secure Sharing of Personal Health Records in Cloud Computing Using Attribute- Based Encryption. IEEE Trans. Parallel Distrib. Syst., 2013. 24(1): p. 131-143. 2. Parsonson, L., et al., A Cloud Computing Medical Image Analysis and Collaboration Platform, in Cloud Computing and Services Science 2012, Springer New York. p. 207-224. 3. Poole, C., et al., Radiotherapy Monte Carlo simulation using cloud computing technology. Australasian Physical & Engineering Sciences in Medicine, 2012. 35(4): p. 497-502. 4. Shen, B., Translational biomedical informatics in the cloud: present and future. Biomed Res Int, 2013. 5. Wu, R., Secure sharing of electronic medical records in cloud computing 2012: ASU.
3. What does Person Focused Health Technology Management mean in practice? 1Amoore J N, 2Brooks-Young P 1Medical Physics, NHS Ayrshire and Arran, 2Edinburgh Napier University/NHS Lothian email: [email protected] Background: National healthcare strategy reflects calls in media and medical literature for person-centred care (1,4,5). Those who support and manage medical devices must now re-focus their approach to Health Technology Management (HTM) to explicitly consider the patient’s needs. Person-centred care transforms care from patient as recipient to patient as participant, recognising each patient’s individuality, knowledge and experience. The approach sounds comforting, supportive. But what does this means in practice for medical equipment and its management? Methods: The literature was reviewed to understand the patient centric approach, why it needs explicit expression and how to apply it to HTM. Models of traditional HTM were compared with person-centric HTM. One-to-one interviews with patients were conducted. Results: Traditional HTM focuses on the equipment whilst recognising relationships between equipment, healthcare team, patient and supporting infrastructure. Equipment focus is important for ensuring safety, effectiveness and on-going maintenance. But on its own it is insufficient - patient and carer focus is required to ensure quality and safe healthcare. Medical technology can be disturbing and even frightening. “It was awful seeing my mother connected to all those tubes and wires.” “Is it because I am about to die that you are connecting me to that pump?” ECRI described healthcare’s transformation “from a provider-based model to one that recognizes and incorporates the individual patient’s needs and values” (3). To “transform the concept from an amorphous ideal into a clearly attainable goal” ECRI recognised the importance of defining the “elements that are characteristic of patient-centered care”. Elements of HTM are summarised in the table, alongside the additional aspects that need to be included in a person centred approach. Phase Traditional HTM Person Centred approach Conception Identify clinical & service need What is needed to benefit each patient’s care? Specification Clinical, Governance, Technical, Define patient perspective: Location of use; after sales support and finance intuitivity; Ergonomics, physical and aesthetics, support Evaluate Look for what is not obvious Evaluate and select integrating the patient perspective and experience Commission Technical commissioning Patient and carer training, Instructions for Use Operational On-going support, problem solving On-going support, how do patients report problems Discussion and conclusion: Person-centred HTM recognises inter-relationships between patient, end- user and device, but with a patient, not device, focus (2). The impact on the patients quality of life should be considered, supporting this by improving their understanding of medical technology and how the technology supports care (1,6). mHealth and care in the community requires cultural change from patients as recipients to patients as partners in their care. The elements of HTM must be transformed from a purely technical focus to ensuring each element supports patient and carer. References 9. Altringer B. The emotional experience of patient care: A case for innovation in health care design. Journal of Health Services Research and Policy, 2010; 15 (3):174-177. 10. Brooks-Young P, Amoore JN. Subcutaneous infusions for pain and symptom control in palliative care: introducing the Keystone model. 19th International Congress Palliative Care, Montreal Canada, Oct 2012 11. ECRI Institute. Patient-centered care. Healthcare Risk Control, Executive Summaries, Volume 2, November 2012. www.ecri.org. 12. Mead N, Bower P. Patient-centredness: a conceptual framework and review of the empirical literature. Social Science and Medicine, 2000 (51): 1087-1110 13. Planetree and the Picker Institute. Patient-centred care improvement guide. Chapter 8: Patient centred approaches to data and technology. Pg 202 to 210. http://patient- centeredcare.org/chapters/chapter8.pdf 14. Quinn C. Infusion devices: understanding the patient perspective to avoid errors. Nursing Times.Net, October 2003.
4. Team work – key to managing major imaging equipment procurement and disposal 1Amoore J N, 2Parker J 1Medical Physics, Crosshouse Hospital, NHS Ayrshire and Arran, Scotland. 2Radiology, Crosshouse Hospital, NHS Ayrshire and Arran, Scotland. email: [email protected] Background. Medical Equipments’ operational journey begins with the identification of need, specification, selection and commissioning and ends with removal from use. These stages are key to ensuring that the optimum safe and effective equipment is available at the point of clinical need and achieving value for money (1). The procurement and commissioning of medical equipment requires a team approach, none more so when involving large imaging equipment with room development requirements. Methods. Projects that created a twin CT room facility and that involved the removal of an MRI scanner that had been replaced were reviewed. The CT project began with recognising the clinical need for an additional CT scanner. The MRI was removed from an internal suite landlocked within the hospital. The processes were reviewed looking at the various people involved and their contribution to the success of the projects. Results. The creation of a twin CT facility began with the requirement for an additional CT scanner. Clinically led, based on current and projected increasing demands for CT scans, the recognition provided the strategic reasons for the hospital’s executive management to seek and approve funding. Installing an additional CT facility requires identifying space and building the infrastructure. Scenario accommodation planning of the busy radiology department and a favourable offer for the early replacement of the existing CT scanner led to the decision that it was cost-effective to develop a twin CT facility, designing the new facility to better improve patient flows and to improve the radiology staff work flows. Clinical directors, hospital management, finance, radiology and medical physics developed the overall proposal supported by Capital Planning and Estates. The hospital was supported by the NHS Scotland National Imaging Equipment Group, formed to co-operate on imaging equipment procurements and maintenance agreements. The detailed process of planning the installation was led by the Head of Radiology who convened a working group that included Estates, Capital Planning, Infection Control, Health and Safety, Fire Officer, Hotel Services, CDM Co-ordinator, Medical Physics and Radiology. Active links were kept with Management and the Directorate of Finance and the team was joined by the Imaging Supply Company and Building Contractor when appointed. The process was not without problems, but the team work with clear leadership allowed these to be solved resulting in a successful installation. Consultation and teamwork were also crucial to the successful removal of a 6 tonne magnet from an MRI room sited deep within the hospital. Various approaches to its removal were considered including dismantling, pushing along corridors and even airlifting with a helicopter before developing a solution involving the erection of a 90m-span crane built overnight at a base in front of the hospital. Differences of opinion were listened to and addressed and the removal plan agreed with appropriate risk assessments developed and risks minimised. Multi-disciplinary hospital staff teamwork with clear leadership, complemented by beautiful team work from the crane company led to the successful removal of the old magnet and its transfer to the purchasing company it. an Discussion and Conclusion. Both processes required multi-disciplinary teams from within the hospital, bringing together their various skills, competencies and responsibilities. The in-house team cooperation required to be linked with team working from outside contractors. Complex projects of this nature involving specialised medical equipment within a hospital setting ensuring minimum disruption to existing clinical services required clear firm leadership that brought together the diverse parties working to a common goal. Key references. 1. Hinrichs S. A Systems Approach to Improving Patient Safety through Medical Device Purchasing , PhD Thesis, University of Cambridge, 2009
5. Feasibility of delivering total body irradiation using helical VMAT on a linear accelerator Bedford J, Gieryluk P, Nurse J, Mayhew P, Thomas M, Ingram W, Chajecka-Szczygielska H Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, UK email: [email protected] Background. Total Body Irradiation (TBI) is commonly delivered on a linear accelerator using an extended focus-to-surface distance. However, treatments of this type are difficult to set up and verify, as the imaging systems on the accelerator are not available for this geometry. Volumetric modulated arc therapy (VMAT) is therefore of interest [1, 2]. This study investigates the feasibility of using helical VMAT to deliver TBI and compares helical delivery with axial delivery. Methods. An anthropomorphic phantom was CT-scanned and the AutoBeam inverse treatment planning system was used to create helical treatment plans. The objectives were to minimise the root-mean-square dose variation around 14.4 Gy, while maintaining the mean lung, kidney and brain doses between 12.0 Gy and 12.5 Gy. Plans using alternating helical arcs and continuous helical arcs were compared with plans using multiple transaxial arcs, all with a longitudinal translation of 20 cm per rotation. Final dose was calculated in Pinnacle3. The accelerator couch was adapted to allow the voltage from a programmable power supply to control the speed of translation. The plans were delivered using the translating couch and verified using TLDs in the phantom. The head section of each plan was also verified using a Delta4 phantom. Results. The plans use eight arcs, and figure 1 shows the dose distribution for the helical plan with alternating arcs. Dose coverage is mostly uniform, with the exception of the top of the head, where coverage is lower due to starting the arcs, and the arms, where coverage is lower due to the limited radius of treatment. Table 1 gives the results of the TLD and Delta4 measurements for the three types of plan. The time for delivery of all plans is in the order of 20 minutes.
PLAN TLD DELTA4 (Mean ± SD Measured vs (% measurements calculated dose) within 3% and 3 mm) Transaxial arcs 5.5 ± 8.3 95.0 Alternating helical arcs -5.4 ± 8.1 96.2 Continuous helical arcs 5.3 ± 5.1 96.0 Table 1 (above). Verification results. Figure 1 (right). Coronal view of the body phantom showing the alternating arcs plan. The isodoses are 70%, 80%, 90% and 107% of the prescribed dose (14.4 Gy). Discussion. This method allows treatment of the whole body with the accelerator operating in the normal isocentric geometry, thereby allowing verification of the patient position and dose using cone-beam imaging or portal dosimetry. The limited travel of the couch is a drawback, requiring that the patient is reversed mid- way through treatment. The limited radius of treatment is also a constraint on the method. Conclusion. TBI can be feasibly delivered on a linear accelerator using helical VMAT with alternating arcs, with plan quality equivalent to transaxial delivery. However, there are some practical questions to be addressed before implementation. We acknowledge NHS funding to the NIHR Biomedical Research Centre for Cancer. Key references. [1] Fogliata A, Cozzi L, Clivio A, Ibatici A, Mancosu P, Navarria P, Nicolini G, Santoro A, Vanetti E and Scorsetti M. Preclinical assessment of volumetric modulated arc therapy for total marrow irradiation. Int. J. Radiat. Oncol. Biol. Phys. 80: 628-636 (2011). [2] Aydogan B, Yeginer M, Kavak GO, Fan J, Radosevich JA and Gwe-Ya K. Total marrow irradiation with rapidarc volumetric arc therapy. Int. J. Radiat. Oncol. Biol. Phys. 81: 592-599 (2011).
6. Toward accurate small photon field dosimetry using radiochromic film Billas I, Silvestre I, Bouchard H, Radiation Dosimetry Group, National Physical Laboratory, Teddington, UK. email: [email protected] Background. While the IAEA workgroup is on its way to developing a protocol addressing small field dosimetry, beam-specific quality correction factor data, which can be determined experimentally or with Monte Carlo methods, is currently in need. The IAEA recommends three measurement techniques for that purpose, among them is radiochromic film which has the advantage of being easily accessible. However, due to recent changes in the manufacturing process, film emulsion thickness uniformity of available models (i.e. EBT3) is not as reliable as its predecessors (e.g., EBT, HS, MD-55). Although the only current manufacturer provides a software solution for that matter, the approach is orientated towards QA applications and do not allow fulfilling accuracy requirements of non-standard beam reference dosimetry. To achieve such goal, developing a reliable approach is needed. Methods. The present work focuses on improving the performance of radiochromic film by combining a controlled experimental environment and a novel multichannel method correcting for film uniformity imperfections. The multichannel correction method is developed from first principles based on the statistical behaviour of optical density for given doses and rectifies defects in film emulsion thickness uniformity. A cobalt-60 beam is used to irradiate films homogenously, allowing determining parameters for scanner homogeneity correction, multichannel analysis as well as film dose response calibration. Measurements of well-known dose distributions are analysed and a thorough uncertainty analysis is done to evaluate the performance of the method in correcting systematic errors due to film non-uniformity. Results. A comparison between single channel analysis and the new multichannel method shows significant improvements in determining absorbed dose accurately. Uncertainties in determining output factors with the procedure are 1.2% (1) for single measurements and 0.4% (1) for measurements repeated 10 times. Consistency in measuring dose distributions of known beams show systematic errors up to 10% with single channel analysis, while they are on average diminished by a factor up to 3 when using the multichannel method, leaving these errors below statistical uncertainties The below figures show a comparison of the methods in measuring a 10 x 10 cm2 cobalt-60 beam profile: a beam profile (left) and a dose map (right).
Discussion and conclusion. Results clearly demonstrate the potential of the method for accurate dosimetry applications by reducing systematic errors due to film non-uniformity to the expected statistical behaviour. Predicted uncertainties for measuring quality correction factors are similar to the ones reported in literature with EBT film. Conclusion. This study proposes a controlled experimental procedure and an analysis reducing systematic errors due to film manufacturing. Potential applications are beam characterization and experimental determination of quality correction factors for small photon fields. References. 1) Alfonso et al., Med. Phys. 35 (2008); 2) Bouchard et al. On the characterization and uncertainty analysis of radiochromic film dosimetry, 36 (2009); 3) Chung et al. Investigation of three radiation detectors for accurate measurement of absorbed dose in nonstandard fields, 37 (2010); 4) Micke et al. Multichannel film dosimetry with nonuniformity correction, Med. Phys. 38 (2011); 5) Saur and Frengen, “GafChromic EBT film dosimetry with flatbed CCD scanner” Med. Phys. 35 (2008)
7. Improving the efficiency of clinical brain VMAT treatments 1Cooke G, 1Golby C, 1Seaton L, 1Erridge S, 1Peoples S 1Edinburgh Cancer Centre, Western General Hospital, Crewe Road South, Edinburgh, EH4 2XU email: [email protected] Background
At Edinburgh Cancer Centre, conventional brain treatments are in the process of being replaced with volumetric modulated arc therapy (VMAT), which has been shown to be a clinically useful treatment technique [1,2]. A study has been carried out to investigate a more robust clinical solution for VMAT brain planning in order to reduce planning time and improve the efficiency of treatment delivery. Methods Patients previously treated with conventional brain radiotherapy for 60Gy in 30# were re-planned utilising both single and two arcs. Parameters investigated in this study include clinical acceptability, number of arcs, monitor units and treatment delivery time. Results Our initial findings show that it is possible to generate clinically acceptable single arc treatment plans. However, as the complexity of the treatment volume increases, the conformality of the single arc plans was found to diminish compared to those with two arcs. The number of MU required to deliver a clinically acceptable single arc plan was found to be comparable to a two arc plan. As the gantry speed was found to be constant for each arc delivered, the beam on time of each plan was also comparable. Discussion It is desirable to be able to generate clinically acceptable single arc brain VMAT plans in order to both reduce planning and optimisation time, and to realise additional minor efficiency improvements in treatment delivery. However, an investigation of the verification dosimetry of the treatment plans will be required in order to ensure that the accuracy of dose delivery is not sacrificed in order to improve throughput efficiency. Conclusion Initial results show clinically acceptable plans, with comparable MU, can be produced for VMAT brain using one or two arcs. Further investigation will be required to establish how many arcs will be necessary for clinically and dosimetrically optimal VMAT brain plans. Key references [1] Comparative dosimetric study of three-dimensional conformal, dynamic conformal arc and intensity- modulated radiotherapy for brain tumor treatment using Novalis system M Ding et al, International Journal of Radiation Oncology, Biology, Physics, 66 (4), 2006 [2] A comparison of volumetric modulated arc therapy and conventional intensity-modulated radiotherapy for frontal and temporal high-grade gliomas R Shaffer et al, International Journal of Radiation Oncology, Biology, Physics, 76 (4), 2010
8. Thinking outside of the line- Use of 2D chamber array to optimise beam symmetry on Elekta Agility linacs Coomber H, Haynes J, Fletcher S, Gregory Radiotherapy Physics Unit, Bristol Haematology and Oncology Centre, Bristol, UK. email: [email protected] Background Traditional reports (1,2) may no longer hold relevant beam specifications in the light of novel therapies including VMAT. Recent commissioning of two Elekta Agility linacs and the availability of a 2D chamber array (MatrixX) attached to the linac head, has caused us to scrutinise how our beams are set up and to re-think our QC programmes(3,4). Small MU segments (as used in IMRT step and shoot) must be examined in addition to running large MU standard delivery(5). Methods. Look up tables set the beam steering of Elekta linacs at different gantry angles according to direction of gantry rotation. Initial table set up was performed by the Elekta engineer without local involvement. Significant (>3%) asymmetry, and variation in asymmetry, was observed when looking at cardinal gantry angles, depending on direction of rotation and large and small segmented MU. This was optimised using MatrixX to assist in the setting of table values by providing live 2D images of the beam. Omnipro IMRT software was used to determine beam symmetry according to IEC protocol and gamma analysis performed to assess day to day beam stability. Final settings were chosen as a compromise when considering all the variables. Results. Variation of symmetry with gantry angle initially ranged from 0.5% (gantry 0) to 2.9% (gantry 180) (AB direction). Following adjustment to look up tables and beam steering, symmetry achieved was 0.3% (gantry 0) and 0.42% (gantry 180). Typically, variation of symmetry with direction of rotation gave a change of symmetry from 0% (clockwise) to 2.1% (counter clockwise) which was adjusted to give 1.3% and 0.8% with opposite tilt (fig a + b). Day to day stability was excellent (mostly within 0.5%) and at worst 1.2%. The gamma map (fig. c) demonstrates better than 1% or 1mm agreement between two days’ measurements.
Discussion and conclusion. The online analysis of beam steering showed the direction of asymmetry which was often diagonal rather than on axis. The MatrixX 2D chamber array is an invaluable tool for setting up beam symmetry, using the live image to show asymmetry off-axis. It has changed our approach to routine linac QC, and adjustments are no longer made on the basis of gantry zero results alone and the direction of rotation is also considered. The symmetry of Elekta Agility linacs beams under the conditions investigated can be brought into manufacturers and local expectations, however some effort is required using a 2D array to fully facilitate this. Routine IMRT QC with the same equipment identifies any drift in symmetry which can then be addressed. Key references. 1IPEM Report 81, Edited by Mayles WPM et al 1999 2IEC Publication 976, 1989 3Bedford JL, Warrington AP. Commissioning of volumetric modulated arc therapy (VMAT). Int. J. Radiation Oncology Biol. Phys. 2009; 73: 537–545 4IPEM Report 94, Kirby M et al 2006 5IPEM report 96, 2008, Working party
9. Towards the reporting of uncertainties of isotope GFR measurements 1Cooke J, 2O’Donnell D, 1Cournane S 1Medical Physics & Bioengineering Dept, St. James’s Hospital, Dublin, Ireland. 2Medical Oncology Department, St. James’s Hospital, Dublin, Ireland. email: [email protected] Background. Glomerular filtration rate (GFR) is a metric which describes the rate of flow of filtered fluid through the kidneys. In oncology centres, it is used predominantly for the calculation of chemotherapy doses. Many empirical equations exist which calculate GFR from serum creatinine levels. However these are based on population averages and are inaccurate for the cancer patient population4. Inaccurate GFR values can therefore lead to under- or overdosing with chemotherapy, to the detriment of patient outcomes. While the isotope GFR method is the gold standard for oncology patients4, it is not currently possible to assess the accuracy of the measurement2,5,6, an issue which is addressed in this study. Methods. In our centre the isotope GFR procedure involves the administration of a specific activity of Tc- 99m labelled diethylene triamine pentaacetic acid (DTPA) followed by blood sampling at three time points thereafter3. The exponential fit of the plasma clearance values at these time points can be then used to calculate the rate of filtration, corrected for body surface area (BSA). In this study we compared the results of the serum creatinine based calculated values (e.g. Jelliffe-Jelliffe, Cockcroft-Gault) to the isotope GFR results. Next, a propagation of errors method1 was devised to calculate the overall error for each patient undergoing an isotope study. This was based on the uncertainties present in respect of all physical measurements including the weights of the isotope, the error in measurement times and the plasma counts. Analysis of the GFR measurements of 82 oncology patients for carboplatin dosing was performed to establish the contributing factors to the error on the measurement. Multivariate analysis was performed which demonstrated the significance of each of the measurement errors on the overall GFR error. During the study we implemented method changes to attempt to improve the measurement error. 27 of the 82 patients had GFR measurements performed with the refined protocol. Results. On comparison of the isotope GFR measurement with the calculated values using creatinine for each patient the mean percentage difference was 21.4% (range -43.3% to 48.5%). The propagated percentage error on the isotope GFR measurement as calculated using the original protocol3 (prior to optimisation) showed the average error to be 14.1% (±6). The multivariate analysis performed demonstrated that the most significant contribution to the overall error was the error on the counts of the duplicate plasma samples. A significant reduction in error resulted from the optimisation of the isotope GFR procedure, t(55,27)=5.37, p=4E-07, with the mean error reduced to 8.5% (±3.4). Discussion. As expected4, creatinine based calculations of oncology patients in our centre did not accurately agree with the gold standard isotope GFR. Using our novel propagation of errors method and multivariate analysis, we reduced the error in our protocol, identifying the elements in the procedure contributing to a reduced error. The mean error on patient measurements has decreased significantly using the amended protocol. Conclusion. While isotope GFR is considered to be the gold standard for accurate establishment of kidney function, no calculations or studies of the uncertainty of these measurements have been performed to date. Consequently, we have devised a novel propagation of errors technique through the complex calculation using differential and regression methods. This allows us to quote GFR values with precise uncertainty to the clinicians for carboplatin dosing, and use the technique as an audit tool for refining the iGFR measurement. References 1. Bevington PR, Robinson DK, Data reduction & error analysis for the physical sciences (1992) McGraw- Hill 2. Bird NJ et al, Nucl. Med Commun (2008) dec;29(12):1086-92. (using six sample method to validate slope intercept) 3. Fleming JS et al, Nucl Med Commun (2004) Aug; 25(8):759-69. (BNMS guidelines) 4. Hartlev LB et al, Eur J Nucl Med Mol Imaging (2012) 39:1478-1482. (tracking gfr in onc pts) 5. Murray A et al, J Nucl Med Technol (2013); 41:67-75 6. Peters A et al, Eur J Nucl Med Mol Imaging (2012) 39:715-722. (reliability in different centres ecfv etc)
10. Electromagnetic Interference (EMI), a case study in collaborative risk management and safety Davie A, NHS Lothian, Royal Infirmary of Edinburgh Email: [email protected] Background The Medicines and Healthcare Products Regulatory Agency (MHRA) provide safety guidance relating to electromagnetic interference (EMI) and medical devices, noting that ‘a range of medical devices can be affected by EMI’ (4). Interference can cause the medical device to change performance or not function at all (1,2,3,5). This case study details a collaborative, multi-disciplinary approach to tackling medical device EMI and ensuring patient safety.
Methods In a specialised cardiac catheterisation laboratory, during an electrophysiological procedure, it was discovered that the hospital’s standard defibrillator immediately disabled when turned on. Three different defibrillators (all the same model) were tried and each immediately disabled when turned on. This was reported as a significant patient risk. A multi-disciplinary team was formed to investigate the cause and implement a safe working procedure. NHS Lothian staff from Cardiology, Anaesthetics, Cardiac Physiology, Radiology and Medical Physics were involved. Application specialists from the medical device manufacturers collaborated in follow-up testing. In order to replicate clinical conditions, the catheterisation lab was set-up with the medical devices that are regularly used, including a C-arm X-ray imaging system, cardiac mapping system and a defibrillator. An oscilloscope was used to visualise and measure the signals present. The testing was repeated in a second catheterisation lab. The defibrillators were also tested in a non-clinical environment.
Results The C-arm X-ray imaging system and cardiac mapping system performed normally (i.e. to their specification). The defibrillators functioned normally outside the catheterisation lab. The defibrillators only disabled when powered on in the vicinity of the cardiac mapping system. This was effect was replicated in the second catheterisation lab. The signal detected by the oscilloscope was complex in nature. However, there was a consistent signal in the 1-2 kHz range. Bench testing of the defibrillator showed that it would alarm and enter a non-operational state when switched on if there was an unexpected signal picked up by the defibrillator pads. This was replicated by applying a 10 mV, 1 kHz signal. Discussion Following the testing the team recommended that an alternative system was used to provide cardiac physiology information. This change resulted in the defibrillators performing normally and mitigated the risk to the patient. Collaboration between the NHS and device manufacturers allowed the nature of the interference to be identified and measured. A software upgrade that changes the way the defibrillator processes unexpected signals has been developed by the manufacturer and is being rolled out to all sites that use the defibrillator.
Conclusion By taking a multi-disciplinary approach, a variety of skills and experiences were applied to mitigate the problem and ensure patient safety. Close collaboration with the medical device manufacturers resulted in the safe continuation of the clinical service and allowed a long term solution to be found. Key references 1. Dang P B, Nel P R, Gjevre J A. Mobile communication devices causing interference in invasive and noninvasive ventilators. Journal of Critical Care. Vol. 22, June 2007, Issue 2, P137–141 2. Jacobsen B, Murray A. Medical Devices use and safety. Churchill Livingstone. 2007 3. Marders J, Witters D. Don't Answer that Cell Phone. Nursing. June 2002, Vol. 32 Issue 6, p87. 4. MHRA. Electromagnetic interference. 2013 5. Putman E. Stiffer Pressure to Move to WMTS Bands… Hospitals Face Higher Telemetry EMI Risks in 2006. Biomedical Instrumentation & Technology. Jan 2006, Vol. 40, No. 1 p22-28
11. Setting up a thermal imaging system for exploratory intra-operative temperature measurements during colorectal surgery 1,3Di Maria C, 1,3Allen J, 2Hainsworth P 1Microvascular Diagnostics, Regional Medical Physics Department, and 2Colorectal Surgical Service, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK. 3Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, UK. email: [email protected] Background. Thermal imaging (TI) [5] has demonstrated its value in various clinical applications, including renal fistula function [2], restless legs syndrome [3], and thyroid eye disease [4]. To date, however, its possible role in colorectal surgery has only been investigated in animal models [6]. Methods. A TI system was set up for intra-operative measurements to meet the appropriate level of electrical safety and sterility requirements. TI measurements were performed in six human subjects undergoing colorectal resection. The thermal camera imaged the bowel being exposed during the surgical procedure which included the segment of bowel to be removed (de-vascularised) and a portion of bowel to be kept to form the anastomosis (Figure 1). The mean temperature across the removed and kept bowel was quantified from twelve consecutive frames for each subject and differences were assessed using the Wilcoxon statistical test.
Figure 4. Example thermal image of the human bowel during colorectal surgery.
Results. The TI system set-up met the required electrical safety and sterility as prescribed by the guidelines of the Newcastle upon Tyne Hospitals NHS Foundation Trust. The TI measurement could be performed in less than 10 minutes. The mean temperature of the kept bowel was significantly higher (p<0.005) than the mean temperature of the removed bowel in all the six subjects; median (Q1-Q3) difference across the subjects 2.3 was (1.4-2.7) °C. Discussion. This exploratory study has demonstrated that thermal imaging measurements can be safely performed in an operating theatre environment during colorectal surgery requiring only minimal interruption of the surgery (less than 10 minutes in the context of a 4 hour procedure). The results have shown that the technology is capable of identifying the temperature characteristics of different parts of the human bowel and differentiating between normal and de-vascularised bowel. Further work is underway to optimise the measurement protocol, explore advanced image analysis techniques, and assess the clinical value of TI measurements in a larger patient group. Key references. 1. Allen J, Howell K. Microvascular imaging: Techniques and opportunities for clinical physiological measurements. Physiol Meas (In press) 2. Allen J, Oates C, Chishti A, Ahmed I, Talbot D, Murray A. Thermography and colour duplex ultrasound assessments of arterio-venous fistula function in renal patients. Physiol Meas 2006; 27:51-60 3. Anderson K, Di Maria C, Allen J. Novel assessment of microvascular changes in idiopathic restless legs syndrome (Willis-Ekbom disease). J Sleep Res 2013; 22:315-321 4. Di Maria C, Allen J, Dickinson J, Neoh C, Perros P. Novel thermal imaging analysis technique for detecting inflammation in thyroid eye disease. (Submitted to J Clin Endocrinol Metab) 5. Ring E, Ammer K. Infrared thermal imaging in medicine. Physiol Meas 2012; 33:R33-R46 6. Urbanavičius L, Pattyn P, Van de Putte D, Venskutonis D. How to assess intestinal viability during surgery: a review of techniques. World J Gastrointest Surg 2011; 3:59-69
12. Development of a daily constancy test for VMAT-like techniques using SunNuclear Daily QA3 devices 1Dixon B J, 2Burke K, 2Walker C 1Radiotherapy Physics, NCCC, Freeman Hospital, Newcastle-Upon-Tyne 2Medical Physics, James Cook University Hospital, Middlesbrough email: [email protected] As part of a move away from patient specific QA towards a process based approach, a daily constancy check for VMAT-like deliveries was designed for measurement on SunNuclear Daily QA3 check devices. This employs a sparse array of detectors to sample a 20x20 area. It then calculates output, flatness, symmetry and an energy parameter based on ratios of individual detector responses. The test was designed to fit within the usual radiographer-led morning QA checks on each linear accelerator with little extra time and effort required. A 240 MU, sliding window, static-gantry sequence was designed with leaf speeds and dose rates close to machine performance limits. Four other ‘known error’ sequences simulating MLC miscalibration were created by editing this sequence, with leaves 2mm offset from, and leaf gaps 2mm wider and narrower than the original test sequence. All sequences were delivered to a QA3 device.. Differences between the ‘known error’ and original sequences for each measured parameter were then used to determine appropriate tolerance levels for daily tests. With these set tolerances, the test consistently highlights uniform ‘gross’ MLC miscalibration (as simulated by the ‘know error’ sequences), as shown in Figure 5. The test and tolerances were checked on four additional matched linacs/QA3 devices and brought into clinical use.
Energy Parameter 20
15
10 Narrow Normal 5 Wide 0 0 2 4 6 8 10 A shift -5
-10
-15
Figure 5: QA3 measured energy parameter for ten repeat deliveries of the original test sequence (Normal) and known error sequences (Narrow and Wide = leaf gaps 2mm narrower and wider respectively, A shift and B shift = all MLCs shifted 2mm towards A and B respectively)
13. A Systematic Review of MRI Ancillary Equipment Safety Labelling in Lothian and Fife 1Douglas J, 1Weir N, 1Department of Medical Physics, NHS Lothian, UK. email: [email protected] Background. Ancillary equipment used in the MR environment requires special consideration to ensure its safe and effective use. The Medicines and Healthcare products Regulatory Agency (MHRA) [1, 2] recommends that all equipment that may be taken into the MR Controlled Area is clearly labelled using ASTM (American Society for Testing and Materials) International standard F2503-05 [3]. At a local MR facility, a ferrous bracket of an ‘MR compatible’ patient trolley became loose and propelled into the scanner. The trolley had been in the department since c1995 and was labelled with blue/white tape, an out-of-date means of labelling items as MR Safe. In 2007, Wilde et al published an analysis of MRI incidents in the UK, with many of these being found to involve ancillary equipment [6]. Examples of adverse incidents involving MRI ancillary equipment include oxygen cylinder projectile incidents [4] and malfunction of infusion devices [5]. In light of the incident in NHS Lothian, a systematic review of ancillary equipment was carried out across 9 MR imaging facilities across Lothian and Fife. Methods. MHRA guidelines stipulate that equipment should be labelled as one of the following: • MR Safe an item which poses no known hazards in all MR Environments • MR Unsafe an item which is known to pose hazards in all MR environments • MR conditional an item which has been demonstrated to pose no known hazards in a specified MR environment with specified conditions of use. The safety status of each item of ancillary equipment was reviewed using a locally produced standard operating procedure. The MR safety status labels were added or amended if necessary. Details of the equipment including a photograph were recorded in a database. The MR Responsible Person was provided with a copy of the database; the contents of which will be reviewed together with the MR Safety advisor at an annual MR safety review. The database is updated as items of equipment are discarded or purchased for the MR controlled area. “MR Unsafe” labels are issued to the MR Responsible Person for attaching to equipment as required. “MR Safe” and “MR Conditional” labels can only be attached to equipment by Medical Physics personnel following appropriate assessment. Results. 47 % of equipment was labelled MR Unsafe, with 34 % and 9 % found to be MR conditional and MR safe respectively. Much of the ancillary equipment was labelled for the first time as a consequence of this review (41 %). MR safety status labels changed for 17 % of items. Discussion. Two main factors were observed to influence the amount of ancillary equipment in the controlled area: (1) case mix and (2) design of controlled area. Most label changes were due to the detection of ferrous components, i.e. a safety status change from MR Safe to MR conditional. Conclusion. A significant amount of ancillary equipment is used in MRI departments. A large proportion of equipment is MR conditional or MR unsafe. The work has reduced the risk of an adverse incident in each MR facility by labelling ancillary equipment and identifying MR unsafe items to be replaced by MR safe/conditional equipment, or removed from the controlled area. The comparative data is being used to encourage existing and new departments to minimise the number of MR Unsafe/Conditional items stored in the controlled area. Key references. [1] MHRA Device Bulletin, Safety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use, DB2007(03) [2] MHRA MR Safety Top Tips (2010) [3] ASTM International. Standard practice for marking medical devices and other items for safety in the magnetic resonance environment. F2503-05 [4] P.M. Colleti, Journal Magnetic Resonance Imaging 19 (2004) 141 [5] C.G. Leeson-Payne, T. Towell, V.L. Englishby, Anaesthesia 51 (1996) 1081 [6] J.P. De Wilde et al. Progress in Nuclear Magnetic Resonance Spectroscopy 51 (2007) 37-48
14. Trends in UK Radiotherapy Physics Research Publications Over the Last Ten Years 1Eaton D J, 2Spezi E, 2Lewis DG 1Radiotherapy Physics, Mount Vernon Hospital, Northwood. 2Department of Medical Physics, Velindre Hospital, Cardiff. email: [email protected] Background. Radiotherapy physics research fosters service innovation and the implementation of advanced treatments into clinical practice. However, lack of resources and academic career routes can be a barrier in many clinical departments [1]. A measure of research output is publication in peer-reviewed journals. This study analysed papers published by UK-based authors in the five most common medical physics and radiation oncology journals between 2011 and 2013. Comparison was then made to a similar study [2] for articles published between 2000 and 2002 to investigate trends over the last decade. Methods. Searches were performed using Web of Knowledge [3] and individual journal websites to identify articles published by author(s) with affiliation: UK, United Kingdom, England, Scotland, Wales or Northern Ireland. Journal titles reviewed were: Physics in Medicine and Biology (PMB) Medical Physics British Journal of Radiology (BJR) Radiotherapy and Oncology (the ‘Green Journal’) International Journal of Radiation Oncology Biology Physics (the ‘Red Journal’) International collaborations were weighted according to the number of UK authors. Radiotherapy physics topics were filtered manually, and included treatment planning, dosimetry, quality assurance, imaging, brachytherapy and clinical radiobiology. Clinician-led planning studies with physics co-authors were given a weighing of 0.5. Results. The total scaled numbers of papers across the three years were 31 (2010), 52 (2011) and 34 (2012). Compared to 2000-2002, this represents a significant increase of over 25%. Fewer papers were published in PMB, but a much greater number in BJR. Output per centre was highly variable, with a few large academic centres producing the majority of the output. Discussion. Research output appears to have increased but the destination of these publications has shifted, possibly reflecting changes in the desired readership, focus of topics in these journals or increased international competition. The majority of publications are produced by a small number of centres, suggesting that many clinical departments do not have the resources to conduct substantive research. Conclusion. UK radiotherapy physics research output appears to have increased in the last ten years, but it is likely that resource issues still limit research activity and outputs in many clinical departments. Key references. [1] Mackay et al Br J Radiol 2012:85;1354-62. [2] Lewis DG. Scope 2003:12/3;9-10. [3] http://wok.mimas.ac.uk/ Thomson Reuters.
15. Feasibility of the performance and energy correction of a novel micro-calorimeter for use in particle therapy Fathi K1, 5, S. Galer1, H. Palmans1, L. Hao2, J. Gallop2, A. Nisbet3, 4, K. Kirkby5 1Acoustic and Ionising Radiation, National Physical Laboratory, UK 2Time Quantum and Electromagnetics, National Physical Laboratory, UK 3Medical Physics, Royal Surrey County Hospital, Guildford, UK 4Physics, University of Surrey, Guildford, UK 5Electronic Engineering, University of Surrey, Guildford, UK Email: [email protected] Aim and purpose: The present work is part of a feasibility study on the development and performance of a novel micro- calorimeter based on Superconducting QUantum Interference Devices (SQUIDs). Unlike other microdosimetric detectors, our detector provides a direct measurement of energy deposition at the micrometre scale, for the comparison of the radiation quality of different treatment modalities in particle therapy. Method and Material: Energy is deposited by the passage of particles through a dual absorber within the SQUID loop consisting of a superconductor and a Tissue-Equivalent (TE) part. Temperature rise of less than 1 µK in the superconducting absorber are readily detectable from the output signal variation of the SQUID. Extremely high energy sensitivity (10000× that of gas chambers) is achieved given the temperature rise with the low specific heat of the superconducting absorber at cryogenic temperatures [1]. However, the energy deposited in the TE absorber is of interest, which can be derived from thermal effect on the superconducting absorber. Therefore direct energy deposition by the traversing protons or ions within the superconducting absorber needs to be corrected for. Geant4 (version 9.6.01) Monte Carlo simulations were performed to determine the expected distribution of proton tracks within the detector. These data were then used as input to model thermal diffusion for the TE correction factors, employing COMSOL Multiphysics, finite element software. Results: Microdosimetric Spectrum at 3.8MeV Proton beam The code exhibited a good agreement with previously 1.20 obtained results by verifying the microdosimetry 1.00 spectra (figure1). Superconducting
0.80 absorber The spatial position and the amount of energy TE absorber deposited with each particle interaction of a proton 0.60 beam with energies ranging from (1.5 – 250) MeV, d(y) * y 0.40 were determined. 0.20 Thermal relaxation was observed from preliminary 0.00 1 10 100 1000 thermal model. y (keV/µm) Figure 1: the dose distribution “d (y)”, versus the lineal energy “y” obtained Conclusion: from the simulations. It is concluded that the temperature rise in the TE absorber can be derived from the temperature rise detected. Work is in progress to model the individual interactions in the COMSOL software to characterise and differentiate between the temperature rise of the superconducting absorber due to direct particle interaction and thermal conduction via TE absorber. [1] L. Hao et al. Inductive Superconducting Transition-Edge Photon and Particle Detector. IEEE Transactions and Applied Superconductivity. Vol 13, No 2, 2003.
16. Regional audit of patient doses from kV linac gantry imaging Hartley A, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke’s Hospital, Cambridge Email: [email protected] Background. There are an increasing number of linear accelerators in radiotherapy departments that have kV imaging technology built into the linear accelerator gantry, allowing two dimensional kV verification imaging to verify and correct patient positioning.[1] Each time an exposure is made there is a resultant dose to healthy tissue, which adds to the concomitant exposure received by the patient.[2, 3] The aim of this study was to assess the magnitude of doses from 2D kV exposures and whether there is scope for optimisation as required for regulatory compliance [4, 5]. Methods. Exposure settings for AP and lateral projections for 4 anatomical regions were collected for 9 systems including 1 Varian Truebeam, 6 Varian Clinac and 2 Elekta XVI systems from 4 hospitals. Clinical protocols indicating the frequency of verification imaging were also obtained. X-ray tube dose measurements were used in conjunction with the provided exposure settings to determine air kerma incident on the patient, which was then used to calculate entrance surface dose (ESD) assuming a 20cm thick patient centred at the isocentre and a 30% backscatter factor. Results. The following graph shows a summary of the results with the main columns indicating the mean
ESD for each projection and the error bars indicating the range of ESD for each projection.
(mGy) Entrance Surface Dose Dose Surface Entrance
Discussion. A large variation in ESD between hospitals was noted with further results indicating Diagnostic Mean Linac Ratio that this variation is mainly attributable to variation in Projection DRL ESD kV imaging Diagnostic/Lin exposure parameters employed by each hospital. (mGy)[6] ESD (mGy) ac Optimisation had been undertaken at one hospital AP/PA Head 1.8 0.5 3.5 with the consequent reduction in ESD clearly shown Lat Head 1.1 0.2 6.1 in the results. The use of ESD is beneficial as AP/PA Thorax 0.2 1.2 0.2 comparisons between equipment and hospitals may be made and patient specific organ doses can be Lat Thorax 0.5 2.4 0.2 determined. Comparisons can be made with AP Pelvis 4 0.5 7.4 diagnostic radiography reference doses (DRLs) and AP Abdo 4 2.0 2.0 Lat: Lumbar radiotherapy concomitant doses to illustrate their Spine / Abdo / 10 4.1 2.5 relative magnitudes. Review of the clinical protocols Pelvis suggests that each patient will receive multiple exposures over the course of treatment, which contributes to the overall concomitant dose to each patient. Conclusion. There is wide variation in ESD between systems and hospitals thus suggesting that there is scope for optimisation of kV linac gantry imaging exposures. Key references. [1] The Role of In-Room kV X-Ray Imaging for Patient Setup and Target Localization (Report 104), AAPM, 2009 [2] The management of imaging dose during image-guided radiotherapy, Report of the AAPM Task Group 75, Medical Physics, Vol 34, 2007 [3] So You Think You Know IGRT? Radiotherapy Imaging: Goals, Challenges and the Diagnostic Basics (Presentation), Una O’Doherty, HPA, 2010 [4] The Ionising Radiation (Medical Exposure) Regulations 2000 (SI 2000 No. 1059). London: [5] The Ionising Radiations Regulations 1999 (SI 1999 No. 3232). London: HMSO [6] Hart, Hillier and Shrimpton, HPA-CRCE-034 - Doses to Patients from Radiographic and Fluoroscopic X- ray Imaging Procedures in the UK – 2010 Review, 2012
17. Identifying High Dose Regions in the Mandible to Aid Restorative Dental Work following Radical Radiotherapy. Barber AJ1, Benson RJ2 , Hague T3, Hutchinson K3 1 Department of Oral and Maxillofacial Surgery 2 Department of Oncology 3 Department of Medical Physics Cambridge University Hospitals NHS Foundation Trust. email: [email protected]
Background. Radiotherapy in combination with chemotherapy and/or surgery is a well established treatment for malignancies in the head and neck (H&N) region1. Post treatment complication risks include the development of mandibular osteoradionecrosis following surgery to the mandible in the high dose region. By optimising oral health prior to radiotherapy, restorative dentistry plays a key role for patients in trying to reduce the need for mandibular surgery following radiotherapy. Recent advances in treatment techniques have created a need for a more prescriptive method for identifying the areas at high risk of osteoradionecrosis. In our centre the majority of H&N patients are treated using helical Tomotherapy, which has limited scope for displaying 3D isodoses. A new procedure was therefore needed. Methods. A patient’s treatment plan was restored to the original planning system. DICOM export tools were employed to export the planning CT, structure set and dose cube to the Pinnacle treatment planning system. The accuracy of dose display in the new planning system was assessed against the original treatment plan. Using 3D rendering tools and by creating volumes of interest from selected isodoses; a 3D visualisation of high dose regions was able to be created. Results A variety of views can be created by freely rotating the dataset. Lateral, inferior oblique and superior oblique views were generated and used by the Restorative Dentistry/Oral and Maxillofacial Surgery team to help inform clinical decision making and aid in the patient education and consent process. Discussion Review of the images was found to help visualise the areas at future risk of osteoradionecrosis and guide treatment planning for surgical dental implant placement in the mandible. Following the single patient trial; a robust method for producing and checking these 3D images was established and documented. Future requests for these visual aids can now be efficiently acted upon and produced. Conclusion. A simple method has been established to assist maxillofacial surgeons in identifying areas at high risk from osteoradionecrosis in patients presenting following radical radiotherapy. References:
1) S Nabil & N Samman: ‘Risk factors for osteoradionecrosis after head and neck radiation: a systematic review’ Oral Surg Oral Med Oral Pathol Oral Radiol 2012; 113:54-69
18. Objective Noise Evaluation in Digital Mammography, towards Image Quality tracking of Clinical Images 1Ivory A, 2Walsh C, 2Cournane S. 1School of Medicine, Trinity College Dublin, Ireland. 2Department of Medical Physics & Bioengineering, St James's Hospital, Dublin 8, Ireland. email: [email protected] Background European guidelines for assessing image quality of Full Field Digital Mammography (FFDM) systems recommend measurements taken using unprocessed images of non-anthropomorphic test objects on an annual basis.[1] These tests are preformed on raw unprocessed images and do not assess the clinically relevant image processing algorithms of clinical images and, due to the frequency of testing, for a period of time a reduction in image quality may go unnoticed. To date no objective image quality analysis techniques for ongoing assessment of clinical mammography images have been suggested in the literature. The purpose of this study is to identify and assess potential noise measures for continuous objective image quality evaluation of clinical images in digital mammography.
Methods A number approaches were investigated to measure the noise present in mammography images. A percentage noise method, based on a noise threshold established using wavelet coefficients, similar to that used by Luo et al. [2], was employed. Variance of parameters from a power law fit of the NPS, as proposed by Cockmartin et al. [3], was also examined. Initial investigations were carried out on both raw and processed images of uniform physics phantoms and anatomical test objects by varying imaging parameters and computationally incorporating noise.
Results In preliminary tests, both methods investigated indicated computationally simulated noise levels in images. On investigation of processed images for physics phantoms and anatomical test objects, the wavelet threshold method gave little variation in percentage noise. The NPS beta fit parameter displayed variation similar to standard noise measurements currently preformed on raw images.
Discussion Application of the NPS method retrospectively to clinical images in normal operation and in the weeks preceding a detector failure will be investigated and the method adapted to develop an objective metric applicable to clinical images on a continuous basis in a remote setting.
Conclusion This work investigates a novel application of noise power spectrum evaluation for the purpose of monitoring changes in noise in clinical images, if successful this method could be incorporated into a remote image quality monitoring system in the future.
Key references [1] European Guidelines for Quality Assurance in breast cancer screening and diagnosis, Fourth Addition, Health and Consumer Protection, Directorate General [2] Luo et al., Journal of Remote Sensing, 2006, 27(22):5003-5025 [3] Cockmartin et al, Medical Physics, 2013, 40,081920
19. Establishing sensitivity factors for contamination monitors 1Kamali-Zonouzi P, 1Smout A, 1 Hollaway P, 1 Hinton P J, 1 Pryor M 1Medical Physics, Royal Surrey County Hospital, UK. email: [email protected]
The aim of this project was to determine the sensitivities of three locally used types of contamination monitors with a range of clinically relevant radionuclides. These were a 900 series Mini-monitor with type 44A probe, a Radhound monitor with type SS404(AL) probe and a Lablogic monitor with type SD-10 probe.
Standard solutions of Tc-99m, I-123, In-111, I-131, Ra-223 and F-18 were prepared containing around 50MBq in 4ml in Schott vials. An accurate assessment of the radioactivity was then made using a secondary standard Fidelis radionuclide calibrator. For each sensitivity measurement the solutions were diluted by a factor of 1000 (by weight) to a final activity of around 50kBq in 50ml. This liquid was placed in a bespoke circular dish of area 100cm2 made from a low Z material (Delrin) which was sited on a 10cm block of polystyrene in order to reduce backscatter. Each probe was aligned coaxially with the dish and positioned so that the window was 10mm away from the surface of the liquid. Instantaneous count-rates were read for the Mini-monitor and Lablogic probes and a 10 second integrated count was used for the Radhound.
Sensitivities in terms of counts per second per Bq.cm-2 have been derived for the above radionuclides and monitors in very specific and reproducible geometries. These have been compared with type test data (where available) and used to derive action levels in terms of counts per second as required by the regulators.
In reality, in an actual contamination situation, the geometric variations from the above set-up would render these sensitivities irrelevant, and although this is our best attempt at calibrating the monitors it is probably more appropriate to use this technique to ensure that the monitors have reproducible sensitivities with time and are fit for purpose.
20. Cardiac Devices in Radiotherapy: What’s the problem? How do we deal with it? Lannon C B.Sc (Hons), M.Sc, Gordon Sands B.Sc (Hons), M.Sc, Margaret Moore Principal Radiotherapy Physicists, Triona Brosnahan Senior Physicists, Louise Fahy Senior Physicists. Radiotherapy Department Galway University Hospital, Ireland email: [email protected] Background: In recent years the administration of radiotherapy to patients with cardiac devices such as pacemakers (PM) or internal cardiac defibrillators (ICD) has significantly increased. There is no Irish national protocol for the treatment of patients with cardiac devices receiving radiotherapy which leads to differences in treatment practices1,2. Many studies have been published on the effects of radiation on the internal complementary metal oxide semiconductor circuit and how it might be adversely affected by therapeutic radiation. It has been shown that, if the device is in the primary radiation beam, then damage to the internal circuit may result if the device receives over a certain dose threshold; >1Gy for ICD and >2Gy for PM3,4,5. This can be critical in some patients as the sensing and pacing functions of the devices may be compromised. Newer ICDs have been found to be more sensitive to radiation due to on board RAM chips and high density integrated circuit6. Use of photon energies greater than 10MV increases the likelihood of neutron production which can adversely damage these devices.
Methods. A literature review and international survey was conducted in order to gather evidence to create a protocol for patients with cardiac devices undergoing radiotherapy in University Hospital Galway. The survey consisted of six questions plus a section for comments. This survey was distributed to worldwide medical physics mailing list. The questions included, cumulative dose limit to device (including leads), allowed treatment energies, radiation setup parameters, in-vivo dose measurements and patient follow-up. Results. In total 124 responses worldwide were received. Of the centres which replied to the survey 66% had a 1-2Gy limit on PM generators, 59% had 1-2Gy limit on ICD’s generators and 66% had no limit on the leads. Regarding energy limit 41% limited the photon energy to 10MV or lower. It was reported that 75% of respondents allowed only leads from the device in the direct beam. A number of different radiation detectors were used for measurement of the dose to the cardiac device. These included diodes, TLD’s, OSL’s, Gafchromic film, and mosfets. Only 9% reported that no patient follow-up was carried out. Discussion The survey conducted in this study showed that many radiotherapy centres have implemented the Netherlands protocol. The Netherlands protocol outlines that patients should be treated on a risk category basis. It divides the patients into low risk, intermediate risk and high risk and outlines the steps that should be in place for each category. It also suggests that treating with greater then 10MV can cause adverse affects in the device3. Conclusion This literature review and survey showed that there is a variation from centre to centre in the treatment protocol of patients with cardiac devices undergoing radiotherapy. Many of the survey respondents were adhering to the Netherlands protocol. An institutional protocol is in the process of being adopted at University Hospital Galway using the knowledge from this study.
1. S. Sundar, R.P. Symonds, and C. Deehan, “Radiotherapy to Patients with Artificial Cardiac Paemakers,” Cancer Treatment Reviews, 2005, 474–86. 2. Isobe Tomonori et al, “Effect of Secondary Neutron Beam Generated in Radiotherapy on Electronic Medical Devices,” Nuclear Science and Technology 2 (2011): 524–29. 3. Coen W Hurkmans et al, “Management of Radiation Oncology Patients with a Pacemaker or ICD: A New Comprehensive Practical Guideline in the Netherlands,” Radiation Oncology BioMed Central, 2012. 4. Anushell Munshi et al, “Radiation Therapy Planning of a Breast Cancer Patient with in Situ Pacemaker-Challenges and Lessons,” Acta Oncologica, 2008, 255–60. 5. 5. Coen W. Hurkmans, “Influence of Radiotherapy on the Latest Generation of Implantable Cardioverter-Defibrillators,” International Journal Radiation Oncol Biol Phys 63 (n.d.): 282–89. 6. K. David Steidley and D. Eric Steidley, “Pacemakers/ICD Irradiation Policies in Radiotherapy Oncology” (Radiation Oncology Dept, St Barnabas Medical Center, Livingston, NJ, 07039, Division of Cardiovascular Diseases, Mayo Clinic, Scottsdale, AZ, 85259, n.d.)
21. A Comparison of the Merits of IMRT, VMAT and Tomotherapy for Planning Hippocampal Sparing Whole Brain Radiotherapy 1Lea R, 1Handley J, 1Whitfield G, 2Cashmore J 1The Christie NHS Foundation Trust 2University Hospitals Birmingham NHS Foundation Trust email: [email protected] Background. The hippocampus is a paired structure located centrally within the brain. Its primary function is related to new memory formation. The hippocampus is thought to be radiation sensitive and therefore may benefit from decreased doses during radiotherapy [3]. Various groups have attempted Hippocampal Sparing Whole Brain Radiation Therapy (HSWBRT) using Helical Tomotherapy, VMAT and IMRT [1, 2]. However, no group has published data comparing the relative merits of the three methods, nor have comprehensive details on how to obtain successful dose distributions using these methods been produced.
Methods. HSWBRT plans were created using IMRT, VMAT and tomotherapy as part of the initial stages of a phase II clinical trial. Plans were produced using dynamic machine parameter optimisation (DMPO) for IMRT and smart arc segmentation for VMAT; both were completed using an Elekta Agility beam model on the Pinnacle treatment planning system. Comparisons were made using a variety of metrics including homogeneity index and target coverage for the PTV and max, mean and median doses to the hippocampi. However, reference is also made to practicability including delivery time, quality assurance burden and equipment requirements.
Results. The highest quality plans were produced using tomotherapy however the technological burden this requires makes it less applicable to a large number of centres. Dual arc VMAT plans were shown to be more successful than 9-field IMRT plans with better homogeneity, target coverage and fewer hotspots.
Conclusion. A comprehensive comparison was made of the merits of helical tomotherapy, IMRT and VMAT for the planning of HSWBRT treatments. Both VMAT and tomotherapy are capable of creating high quality modulated treatment plans for HSWBRT. IMRT is able to produce plans with significant hippocampal sparing, however, only at the cost of a loss of homogeneity.
Key references. [1] Awad et al, “Hippocampal avoidance with volumetric modulated arc therapy in melanoma brain metastases – the first Australian experience,” Radiation Oncology, vol. 8, no. 62, 2013. [2] Gondi et al, “Hippocampal sparing whole-brain radiotherapy: A “how-to” technique using helical tomotherapy and linear accelerator-based intensity-modulated radiotherapy,” International Journal of Radiation Oncology Biology and Physics, vol. 78, pp. 1244-1252, 2010. [3] Rola et al, “Radiation-induced impairment of hippocampal neurogenesis is associated with cognitive deficits in young mice,” Experimental Neurology, vol. 188, no. 2, pp. 316-330, 2004.
22. Improved kidney sparing and conformity in abdominal neuroblastoma patients utilising a dual arc VMAT solution McWilliam A., Pinkham M.B., Whitfield G.A., Smith, E. The Christie NHS Foundation Trust, Wilmslow Road, Manchester, M20 4BX email: [email protected] Background: Children with high risk neuroblastoma usually receive adjuvant radiotherapy but proximity of OARs can make planning these with conventional techniques challenging, typically leading to sub-optimal PTV coverage to allow the OARs to be spared. Gains et. al. showed that by using an arc technique PTV coverage could be improved while maintaining or improving kidney doses. However they found two patients with midline tumours were unable to meet the constraints documented in the SIOPEN HR-NBL-1 protocol. We investigated whether with careful control of the optimisation criteria, kidney doses could be further controlled enabling lower doses to be achieved.
Methods: Ten neuroblastoma patients previously treated to 21Gy in 14 fractions with conventional conformal techniques were retrospectively re-planned using VMAT (Pinnacle v9.6/Elekta agility). A dual arc technique (178°-182°) with a 10° collimator angle was used at 6MV. The plans were assessed according to ICRU 62 and 83 and OARs using the SIOPEN HR-NBL-1 protocol. Conformity of the D95% to the PTV was assessed using the dice similarity coefficient (DSC). Statistical significance of the results was assessed using the two-sided paired sample t-test (p<0.05 showing significance).
Optimisation for the kidneys was controlled initially using a maximum dose constraint to the volume outside PTV+0.5cm. For kidneys with significant overlap with the PTV, a series of maximum DVH constraints were applied to the kidney. One controlling the position of the DVH shoulder, one to control the intermediate dose and one to limit the volume receiving high dose. These constraints were reduced iteratively until PTV coverage was tight but not compromised.
Results: Mean PTV volume was 398cm3 (range 234-801cm3); 7 PTVs were lateralised and 3 located centrally. PTV D2%, D98% and mean dose did not differ significantly between conventional and VMAT techniques. The DSC for VMAT was significantly better than for conventional plans. Kidney doses are provided in table 1; the reduction in V12 and V15 was statistically significantly for the contralateral kidney. Liver doses and homogeneity across the vertebral bodies was also improved using VMAT. Ipsilateral Contralateral Conventional VMAT Conventional VMAT Mean (cGy) 1374 1266 283 587 (range) (777 – 2031) (593 – 1815) (124 – 527) (410 – 746) V12 58.7% 48.9% 2.1% 1.8% (range) (14.1% - 100%) (6.0% - 95.7%) (0.0% - 8.6%) (0.0% - 5.7%) V15 47.4% 36.9% 1.1% 0.6% (range) (6.7% - 97.0%) (2.7% - 80.5%) (0.0% - 5.5%) (0.0% - 2.9%) V21 15.0% 9.4% 0.0% 0.0% (range) (0.0% - 74.9%) (0.0% - 34.5%) (0.0% - 0.0%) (0.0% - 0.0%) Table 1, doses for contralateral and ipsilateral kidneys.
Discussion: Intermediate and high dose to the OARs were reduced using a VMAT technique, although the low dose component of the DVH was seen to increase. Considering the high-risk nature of the disease the clinicians accepted the DVHs for the improved PTV conformity.
Conclusion: Careful use of optimisation constraints for kidney sparing allowed the VMAT plans to reduce the V12, V15 and V21 while maintaining or improving PTV coverage.
Key references Gains, J.E. et.al, Intensity-modulated arc therapy to improve radiation dose delivery in the treatment of abdominal neuroblastoma, Future Oncol (2013) 9(3) 439-449
23. Measurement of vocal cord asymmetry to diagnose laryngeal disorders 1Menon R, 1Petropoulakis L, 1Soraghan J, 2Lakany H, 3Omar H, 3MacKenzie K 1Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, UK. 2Department of Biomedical Engineering, University of Strathclyde, Glasgow, UK. 3NHS Greater Glasgow and Clyde, UK. email: [email protected] Background: The larynx, comprised of the vocal cords, is located in the throat and aids in breathing, voice production and swallowing. Endoscopes, inserted through the nose or mouth, enable clinicians to view the vocal cords and perceive any abnormalities. However the evaluation is subjective and causes variability in diagnosis [3]. Researchers have extracted quantifiable features from laryngeal images to improve diagnostic outcomes [4]. Nonetheless, an established procedure is yet to be defined and adopted clinically [5]. We are encouraged by the success of another technology called ‘Facogram’, employed for quantifying asymmetries in paralysed faces [1], to adopt its methodology for developing an objective assessment tool for laryngeal disorders. The Facogram approach is relevant because asymmetries of vocal cord structure and motion are observed in most laryngeal pathologies [2]. Methods: A database of videos of healthy and abnormal vocal cord motion will be constructed. The flexible endoscope will ideally be used for video capture because it is more frequently used in out-patient clinics than the rigid endoscope. Vocal cord edges will then be extracted from the image frames using a threshold based edge detection algorithm. Subsequently, the asymmetry in vocal cord motion can be determined using methods used in the Facogram, namely, optical flow and multi-resolution local binary patterns. Finally, different types of asymmetry can be classified using neural networks, such as Radial Basis Functions. Results: A preliminary study was done for feature localisation of still images of vocal cords. As shown in figure 1, the colour image was converted to greyscale and binarised using its median value as threshold. An outline of the airway between the vocal cords was then extracted. Figure 1: Left to right - Original image from clinic with (encircled) lesion and dark airway between left (LV) and right (RV) vocal cord edges; Binary image of original, clearly showing airway in white and protrusion of lesion from left vocal cord; Outline of airway extracted from binary image.
Discussion: An initial feature localisation algorithm successfully identified the region of interest in laryngeal images with reasonable accuracy. Further refinement and advancement of the algorithms will allow automatic segmentation of vocal cord edges in consecutive image frames of a video. It is anticipated that pre-processing images acquired using flexible endoscopes will be challenging due to difficulties of standardising the angle and distance of viewing the vocal cords. Conclusion: Inter and intra clinician variability in diagnosis of laryngeal disorders is a pertinent issue, particularly when patients are assessed periodically for several months and not necessarily by the same clinician, such as during the course of radiotherapy treatment for laryngeal cancer. By providing a quantitative measure of laryngeal asymmetry to assess vocal cord structure, function and airway, our technique is potentially a powerful diagnostic tool. It also provides a means for establishing an improved system of tracking the progression of laryngeal conditions. Key references: [1] He, S., Soraghan, J., O'Reilly, B. and Xing, D. (2009) 'Quantitative analysis of facial paralysis using local binary patterns in biomedical videos'. IEEE Transactions on Biomedical Engineering, 56 (7), pp. 1864-70. [2] Hirano, M. and Bless, D. (1993) Videostroboscopic examination of the larynx. London: Whur. [3] Olthoff, A., Woywod, C. and Kruse, E. (2007) 'Stroboscopy versus high-speed glottography: a comparative study'. Laryngoscope, 117 (6), pp. 1123-1126. [4] Verikas, A., Uloza, V., Bacauskiene, M., Gelzinis, A. and Kelertas, E. (2009) ‘Advances in laryngeal imaging’. European Archives of Otorhinolaryngology, 266, pp. 1509-1520. [5] Woo, P. (2014) 'Objective Measures of Laryngeal Imaging: What Have We Learned Since Dr. Paul Moore'. Journal of Voice, 28 (1), pp. 69-81.
24. Effectiveness of software corrections to diode angular response in the ArcCHECK device Moloney S Department of Radiotherapy Physics, Poole Hospital NHS Foundation Trust, UK email: [email protected] Background. The ArcCHECK (Sun Nuclear Corporation) is a cylindrical radiotherapy beam dosimetry QA device containing a helical array of diode detectors5. Proprietary software is used to compare the measured dose distribution to that calculated by the TPS. Diode detectors such as those used in ArcCHECK are known to exhibit sensitivity changes dependent on the angle of incidence of the beam. For the similar MapCHECK device such variations were 20% or more3. Due to the different ArcCHECK construction, it was assumed that angular dependences would be insignificant. This was found not to be the case1,2. For large field sizes, diodes at the field edges are irradiated at steep angles, leading to significant sensitivity changes. Sun Nuclear introduced software corrections for this effect4. This work assesses the effectiveness of these corrections. Methods. Diode response variation with beam incident angle was investigated by comparing doses measured with a single ArcCHECK diode to doses predicted by the TPS (Eclipse v10, Varian Medical Systems) at the diode location for varying linac gantry angle. ArcCHECK measurements were carried out with the software corrections switched off and on. The effect of the corrections on the results of gamma analysis for single fields of increasing size was also assessed. Results. ArcCHECK diodes over-respond when irradiated obliquely by up to about +7% relative to the TPS calculation. After software correction, diode measurements agree more closely with planned values, generally to within 1%. The effect of this improvement on gamma pass rates for single fields of increasing size is marked. Without angular corrections, the gamma pass rate (3% local, 3mm) begins to drop sharply at a 16x16cm field size, quickly becoming unacceptable as field size is increased further and diodes at the field edges are irradiated at steep angles. The pass rate is consistently above 96% after angular corrections are applied. Discussion. The diodes in the ArcCHECK device show significant response variation as a function of incident angle. Software correction reduces this variation to an acceptable level. Work to assess the impact of the corrections on the results of gamma analysis for clinical VMAT plans is ongoing. It is anticipated that improvements will be seen, but not as markedly as for the response of individual diodes to single beams as studied here. In VMAT plans, a significant portion of the total dose measured by each detector is received whilst being irradiated at a low angle of incidence, when improvements due to software correction will be small. Conclusion. Software corrections implemented to counteract problems in ArcCHECK diode response variation due to changes in beam incident angle are effective, at least when individual diodes are examined in simple fields. How these corrections influence the result of quality assurance measurements for clinical VMAT plans is the subject of further ongoing work.
Key references. 1. Feygelman V et alia, Evaluation of a new VMAT QA device, or the “X” and “O” array geometries, Journal of Applied Clinical Medical Physics 2011;12(2):146-68. 2. Guangjun L et alia, Evaluation of the ArcCHECK QA system for IMRT and VMAT verification, Physica Medica (2013) 29, 295-303 3. Jursinic PA, Sharma R, Reuter J. MapCHECK used for rotational IMRT measurements: step-and- shoot, tomotherapy, RapidArc. Med Phys 2010;37(6):2837-46. 4. Kozelka J et alia, Optimizing the accuracy of a helical diode array dosimeter: a comprehensive calibration methodology coupled with a novel virtual inclinometer. Med Phys 2011;38(9):5021-5032. 5. Sun Nuclear Corporation 2013, ArcCHECK Reference Guide, Document 1220011, Rev H-2, www.sunnuclear.com
25. Effectiveness of software corrections to field size response variation of the ArcCHECK device Moloney S Department of Radiotherapy Physics, Poole Hospital NHS Foundation Trust, UK email: [email protected] Background. The ArcCHECK (Sun Nuclear Corporation) is a cylindrical radiotherapy beam dosimetry QA device containing a helical array of diode detectors4. Proprietary software is used to compare the measured dose distribution to that calculated by the TPS. Due to similarities with the MapCHECK device, it was initially assumed1,3 that the ArcCHECK diodes would show negligible dependence of results on field size. This was later found not to be the case1,2. Sun Nuclear introduced software corrections for this effect4. This work assesses the effectiveness of these corrections. Methods. Due to the construction of the ArcCHECK, beam measurements are made by diodes in ‘beam entrance’ and ‘beam exit’ positions. Diode response variation with increasing field size was investigated by comparing output factors measured with single ArcCHECK diodes to ion chamber measurements in similar geometries. Diodes in both entrance and exit positions were investigated separately due to the significantly different geometries. ArcCHECK measurements were carried out with software corrections switched off and on. Results. In the entrance diode geometry, ArcCHECK-measured output factors differ from ion chamber results by around -2% to +1.5% in the range of field sizes examined. In the exit diode geometry, the range is -5.5% to +3.5%. The over and under-response are more significant for the exit diode position, presumably due to the increased volume of material above this diode. After software correction, in the entrance diode geometry, ArcCHECK-measured output factors are all within ±0.5% of the ionisation chamber measurements. In the exit diode geometry, the improvement is not as marked, but ArcCHECK-measured output factors are generally within 2% of ionisation chamber measurements. Discussion. The diodes in the ArcCHECK device show significant response variation as a function of field size. Software correction reduces this variation, but gives better results for diodes in the entrance position than the exit position. It is possible that the corrections are optimised for the entrance diode position. This is reasonable as the dose received by an exit diode is in the region of 20-30% of that received by the entrance diode. For a full arc VMAT delivery, each diode will at times be ‘entrance’ and at times ‘exit’. The ‘exit’ contribution to the total dose measured by each diode is a fairly small fraction, around 15% - 25%, so the reduced effectiveness of the corrections for the exit diodes will be less apparent than indicated above. Work to assess the impact of the corrections on the results of gamma analysis for clinical VMAT plans is ongoing. It is anticipated that improvements will be seen, but not as markedly as seen here for the response of individual diodes to single beams. In VMAT deliveries, the total dose measured by each detector is made up mainly of dose received whilst being irradiated by a field of relatively small equivalent square field size, when improvements due to software correction will be small. Conclusion. Software corrections implemented to counteract problems in ArcCHECK diode response variation due to changes in field size are effective, at least when individual diodes are examined in simple fields. How these corrections influence the result of quality assurance measurements for clinical VMAT plans is the subject of further ongoing work.
Key references. 6. Feygelman V et alia, Evaluation of a new VMAT QA device, or the “X” and “O” array geometries, Journal of Applied Clinical Medical Physics 2011;12(2):146-68. 7. Guangjun L et alia, Evaluation of the ArcCHECK QA system for IMRT and VMAT verification, Physica Medica (2013) 29, 295-303 8. Kozelka J et alia, Optimizing the accuracy of a helical diode array dosimeter: a comprehensive calibration methodology coupled with a novel virtual inclinometer. Med Phys 2011;38(9):5021-5032. 9. Sun Nuclear Corporation 2013, ArcCHECK Reference Guide, Document 1220011, Rev H-2, www.sunnuclear.com
26. Potential for high Skin Doses arising from contamination in the Radiopharmacy and Patient administration in Nuclear Medicine. O’Neill J, NHS Tayside, Ninewells Hospital, Dundee Email: [email protected] Background. Following the report that a nuclear medicine technician received a significant occupational skin dose [1] arising from prolonged low level contamination of the skin, the potential doses arising from contamination for two staff groups was investigated: A) Radiopharmacy dispensary workers and B) Nuclear Medicine staff who administer patient Tc-99m radiopharmaceuticals. Aim of this investigation is to estimate potential doses arising from contamination, verify results by experiment and consider if classification of some staff based on their potential for receiving high skin doses from contamination is necessary. In Scotland, 2 out 5 radiopharmacies have designated dispensary staff as classified workers, based on their external extremity dose (exceeding or approaching 3/10ths of the UK equivalent dose limit for the skin/hand). In 3 centres, personal monitoring has demonstrated extremity doses are << 150 mSv per annum and staff remain non-classified. Nuclear medicine staff, are in general, non-classified on basis of low extremity and whole body doses and IRR99 Risk assessments[2]. Methods. Estimation of external skin dose ( extremity dose) by calculation arising from contamination using published dose rates for two geometries [3]. A) Droplet contamination model (gloved hand) for radiopharmacy workers dispensingTc-99m and B) Uniform wide area deposition on the surface of the skin for nuclear medicine staff performing Tc-99m radiopharmaceutical patient injections. For A) short term contamination of gloved hand by droplet modelled by calculation and verified by experiment. For B) both short term contamination ( droplet) and long term uniform residual contamination of skin modelled mathematically. For an initial dose-rate do decaying with a half-life τ½, the dose incurred in a time T is T 0.693 do exp tdt,where = o ½
= 1.44 d o τ ½ 1 exp 0.693T /½ Eq.(1) Results. A) Extremity doses calculated using droplet model and short integration times of 5 mins for Tc- 99m eluate (100GBq) is 73 mSv . For typical activity of 2GBq, an extremity dose of 88mSv per 15 min interval is estimated. Verified by experiment. B) Extremity doses using uniform deposit model [3] and Eq (1) result in doses to the skin of approx 260mSv for handling 0.6GBq with 600 kBq contamination and 20% (120 kBq) remaining after attempted decontamination. Discussion. In A) doses > 150mSv limit for the skin can be obtained in a single contamination event for 15 mins exposure to a droplet of eluate. For repeated droplet contamination accumulated over the year from lower activities more routinely handled and when taken with the external dose measured at the same point, annual finger doses > 3/10 of annual dose limit for radiopharmacy staff could easily be achieved. Consider classification due to potential high doses arising from ‘likely’ contamination. In B) risk is from uniform fixed contamination on skin itself by (120) kBq Tc-99m resulting in dose to skin of 260mSv. Consider covering arms with disposable sleeves for handling and injecting to prevent this contamination risk. Conclusion. A) The results of both the calculations and experimental dose measurement for short term droplet contamination (high specific Tc-99m activity) onto gloved hands, has demonstrated that radiopharmacy staff are at risk from potential extremity doses in excess of 3/10th of UK dose limits. We recommend these staff are classified workers and highlight need for frequent contamination monitoring ( ≤15 minute intervals) for staff working in such situations. B) Nuclear medicine staff routinely administering patient doses of Tc-99m ( 600 MBq per injection) are at risk of extremity (skin) doses arising from direct contamination of the outer surface of the skin. Doses > 3/10ths of the UK dose limit for skin. We recommend such staff wear disposable sleeves to avoid potential for long term low level skin contamination. Key references. ICRU Radionuclide Handbook 2002[3], IPEM meeting : Inspection and Accreditation in Nuclear Medicine 1st October 2013, D. Orr HSE [1], Personal communication from Scottish RPA group, [2]
27. An Innovative Approach for Radiation Centre Identification and Its Applications in Film-less QA Oommen K, Metwaly M Radiotherapy Physics, Beatson West of Scotland Cancer Centre,Glasgow, UK. email: [email protected] Background A precisely localised radiation centre on a linear accelerator can be regarded as the reference point for the inspection of the radiation field boundaries and mechanical centre of the machine. Current approaches to identify the radiation centre involve computing the centre of mass of a field defined by the Primary Collimator, an externally mounted collimator or the Multileaf Collimator (MLC) leaves [1]. In this project a new method for radiation centre localisation on the Electronic Portal imaging Device (EPID) panel based on inner-leaf leakage between the two central MLC leaves is described and implemented using MatLab. Being based on the side-to-side distance between leaves this technique is robust with regard to positional uncertainty, cost effective not having to purchase any new equipment and time efficient as a result of automation using software. Method The technique is based on a set of EPID images of radiation leakage through the central MLC leaves sides with different collimator rotations. The radiation centre position on the EPID panel is taken as the pixel of the maximum dose value when each two images of the set are overlapped individually, following which a general radiation centre is taken as the average of outcome of all combinations. By means of a geometrical approach with an open MLC regular field and the radiation centre images, the angle between the MLC leaves sides and imager pixel rows is determined with zero collimator rotation. An image rotation by this angle is applied for the whole set of images and a new radiation centre is determined to be the radiation centre base line (RCBL) for this set of images and to be the origin of the a Cartesian coordination system on the imager. For evaluation purpose, a MatLab edge function was selected to find the positions of the edge points of an open 10x10 cm MLC field at different off-axis distance. The search for the edge positions at each off-axis distance was preformed across the leaf motion direction where the edge was defined by the MLC leaves sides as it is supposed be fixed and independent of any calibration condition. Therefore the distances between the edge points at the different off axis positions along the leaf motion direction are expected to be consistent, as long as the image is properly aligned, and are used for the calibration of the distances in pixels. Applications: Static MLC QA & Stereotactic Isocentre QA The first application of the RCBL based coordinate system is to analyse EPID images of MLC defined radiation fields so the MLC tip positions could be determined and subsequently, be compared with the expected MLC positions extracted from MLC files from the treatment planning system. The second application of the RCBL system was to carryout the Winston Lutz test [2] where, the difference between the location of the centre of a spherical object aligned to the treatment room lasers is compared to the field centre at various gantry and couch angles as a means of quantifying the linac isocentre movement. Conclusion A new method for radiation centre identification with EPID was developed and tested using MatLab. The method was found to be working correctly for static MLC QA and machine isocentre check. The proof of concept study has now been completed with the aim of carrying out a larger pilot study before routine implementation. Key References [1] Darl j. O'Connor Peter B. Greer Pejman Rowshanfarzad, Masheed Sabet. Isocenter verification for linac-based stereotactic radiation therapy: review of principles and techniques. Journal of Applied Clinical Medical Physics, 12(4):185-195, 2011. [2] N. Maleki W. Lutz, K.R. Winston. A system for stereotactic radiosurgery with a linear accelerator. Int J Radiat Oncol Biol Phys, 14(2):37381, 1988.
28. Registering an expert software as a uro-oncology specialist. Salem H, Awwad A, Thomas S, Peracha A, Amawi F, Henley M. Urology Department, Royal Derby Hospital, University of Nottingham, UK. Email: [email protected] Background. Since the artificial intelligence (AI) birth statement by J McCarthy in 1956, the concept of machine intelligence in simulating expert problem solving has been successfully applied in numerous industrial applications in the form of knowledge storage and manipulation software i.e. Expert Systems (ES). Even though one of the earliest and widely cited rule based ES was developed in medical domain [1], yet the uptake of these systems remain low in the health care possibly due to the challenge of acquiring the complex medical knowledge and the rigorous testing criteria required by the medical device regulatory agencies for software registration. AI in medicine has proven their positive outcome on the practitioner’s performance [2] and they could represent a key solution to the increasing demands in healthcare by providing specialist opinion for managing chronic diseases in the community. Stable prostate cancer (SPC) is an example of chronic disease with a high incidence reaching 80% of all men at the age of 80 that would benefit from this technology and in our research we aimed at developing an ES capable of managing SPC in the community with minimal human supervision meeting the standards of the Medical and Healthcare products Regulatory Agency (MHRA). Methods. The domain knowledge acquisition was performed by unstructured interviews and examining the National Institute for Health and Care Excellence (NICE) guidelines, which led to hand written rule for managing SPC in the form of decision trees. Three independent Urology cancer specialists validated these decision trees against 200 real and synthetic cases and a panel of experts reviewed all the discrepancies suggested by the reviewers. The panel corrected decision trees were used to construct the knowledge base in the form of condition phrases or rules (IF-THEN). This prototype was subjected to further testing on a new set of 51 real cases and the system outcome was compared against the specialist panel suggestions. Results. The panel implemented 9 changes to the hand written decision trees before reaching a consensus on the prototype knowledge for diagnosing disease progression and treating complications of SPC. The hand written knowledge was translated into ES rules to construct the system knowledge base. The prototype testing demonstrated 100% accuracy (95%, CI = 0 - 6.85). Discussion. The knowledge acquisition of these systems is considered the bottleneck for their development. The methodology of this study provides a comprehensive structure to acquire, represent and validate medical knowledge. The hand written rules are simple to validate by solving domain related cases and their framework as decision trees is easily interpreted by the ES developer and translated to knowledge base rules. The national guidelines and specialist panel agreement on the hand written rules together with the evidence from the scientific can support the knowledge base validation up to an acceptable standard by the MHRA which is posing a challenge for developing these systems [3]. Conclusion. The methodology used in this study can bridge the gap in the knowledge acquisition and present objective evidence to support the device registration with the MHRA. Key references. Artificial intelligence, Expert system, Follow up, Primary care, Prostate cancer, Rule based system, Follow up.
References.
1. Shortliffe, E.H., et al., Computer as a consultant for selection of antimicrobial therapy for patients with bacteremia. Clinical Research, 1975. 23(3): p. A385-A385. 2. Kawamoto, K., et al., Improving clinical practice using clinical decision support systems: a systematic review of trials to identify features critical to success. British Medical Journal, 2005. 330(7494): p. 765- 768E. 3. Ammenwerth, E., et al., Clinical decision support systems: Need for evidence, need for evaluation. Artificial Intelligence in Medicine, 2013. 59(1): p. 1-3.
29. The Evaluation of Adaptive Filtering in Improving Respiratory Impedance Estimates 1Scott J R, 2Scott R.S, 1 Undergraduate Student, Department of Mathematics, University College London, UK 2 Medical Equipment Management Department, Sherwood Forest Hospitals NHS FT, Notts, UK email: [email protected] Background Estimating respiratory impedance, using an oscillatory airflow, is an appealing clinical assessment technique for investigating the mechanics of the respiratory system. The subject breathes normally during the procedure, thereby eliminating the need for maximal respiratory manoeuvres which would change the volume history of the lung between successive measurements. The technique involves applying an oscillating random airflow at the mouth, recording pressure and flow and computing the resistive and reactive components of impedance [1]. The normal respiratory system is well described by a linear model comprising a resistor (R), an inductor (L) and a capacitor (C) in series, exhibiting resonance at around 6-8Hz. In the presence of lung disease the simple RLC model no longer adequately describes the data, which becomes characterised by a frequency dependence of resistance. Instrumentation generates a random airflow containing components across a 1-40Hz range, but measured data below 5Hz is typically deemed unreliable and is discarded due to low signal to noise and cardiogenic interference [2]. The technique has failed to achieve its full diagnostic potential due to the lack of data in the 1-5Hz range which is crucial for determining the capacitive elements in models. There has been a resurgence of interest in the technique at Sherwood Forest Hospitals during endoscopic lung volume reduction surgery as the ability to readily assess lung compliance during the procedure would optimise treatment. Therefore the subject of low frequency data reliability has been re- visited, as a prerequisite for developing instrumentation based on previous experience with the technique [3]. The present theoretical study assesses the potential use of adaptive filtering in improving the quality of low frequency data so that good compliance estimates are more readily achieved. Methods The respiratory system was modelled as described above, and an input signal containing components at 1-40Hz was used to generate a simulated flow. The primary source of interference in low frequency data arises from the heart superimposing a second input on the respiratory system (from within the lung). It has a strong component at the pulse rate (approximately 1.0-1.3Hz) and contains various weaker components. Such a signal was generated, and provides a second input to the system. A correlated reference signal was also created, and two adaptive filters were used to attempt to remove the interference from the ‘measured’ input and output of the system [4]. The parameters R L and C were estimated in the presence of noise, using the above method and standard techniques [1], and the results were compared. Results. The ability of the adaptive filters to reduce error in the RLC estimates in the presence of various types of interference will be presented. Discussion. The design of the adaptive filter is crucial to its performance in eliminating the interference. Convergence properties of the adapting process are very important and are affected by the design of the filter and the characteristics of the noise. Optimal noise reduction is therefore obtained by adjusting the specification in accordance with a priori knowledge about the type of noise to be eliminated. Conclusion. The technique is a possible method of improving the quality of low frequency pressure and flow data. The next stage of the investigation will be to implement the system in practice. In particular it will then be possible to exactly characterise the interference and design an optimal filter to remove the noise. This study provides the necessary background for the work. References 1 Pulmonary Mechanics by Spectral Analysis of Forced Random Noise, Michaelson, E.D., Grassman, E.D.and Peters, W.R., Journal of Clinical Investigation, Vol 56, Nov 1975, 1210-1230. 2 The Assessment of Cardiogenic Interference on Respiratory Impedance Measurements, Scott, R.S. and Grant, L.J., Eur. Respir. Rev., 1994, 4:19, 126-129. 3 Determination of Respiratory Impedance via the Oscillatory Airflow Technique, Scott, R.S., PhD Thesis, University of Bath, 1993 4 Adaptive Noise Cancelling: Principles and Applications, Widrow, B., Glover, J.R. Jr., McCool, J.M., et. al. Proceedings of the IEEE, Vol. 63, No. 12, Dec. 1975, 1692-1717.
30. Heart Doses after Left Sided Breast Irradiation at the Beatson West of Scotland Cancer centre. 1 1 2 Small A , Melissa Leitch , Aqilah Othman . 1Radiotherapy Physics, Department of Clinical Physics & Bioengineering, NHS Greater Glasgow & Clyde; 2Beatson West of Scotland Cancer Centre, NHS Greater Glasgow & Clyde email: [email protected] Background: Adverse cardiac effects after radiotherapy have been noted since 1960, when patients receiving treatment for Hodgkin’s lymphoma were observed to have increased rates of heart disease [1]. For these patients, large volumes of the heart were exposed to doses >40Gy and cardiac events were found to be statistically significant 10 years after treatment [2]. Links between radiotherapy in other areas of the body have also been associated with heart disease, for example radiotherapy for peptic ulcer disease [3] and testicular cancer [4] as well as breast cancer [5]. Many studies on the relationship between breast radiotherapy and heart disease have been performed over the years, but [5] investigated a large cohort of patients (963 women with coronary events and 1205 control subjects) who were diagnosed with breast cancer between 1958 and 2001 in Sweden and Denmark. They found that the overall average of the mean heart dose was 6.6Gy for left sided tumours and 2.9Gy for right sided tumours. The rate of coronary events was found to increase by 7.4% per Gy in the mean radiation dose delivered to the heart. This study was performed to determine what heart doses were received by patients and whether there was any difference in this for photon or electron boosts.
Methods: For this study, 20 left sided breast patients, treated with electron boost, between May 2011 and April 2013 were chosen randomly. As this was a random selection it included 13 patients with a 4005cGy in 15 fractions, 4 patients with 5000cGy in 25 fractions and 3 patients with 2700cGy in 5 fractions from the FastForward trial. A photon boost plan was then created for these patients using the FastForward parameters. The dose/fractionation of 1000cGy in 5 fractions was used for every boost plan.
Results and conclusion: The average mean dose recorded within this study of recent breast patients is 1.5Gy for an electron boost and 1.3Gy for a photon boost plan, which is consistent with the results in [5]. However, some patients are receiving a larger mean dose, with the highest being 4.0Gy for a very medial deep tumour treated with an electron boost. There is also quite large variation in the proportion of the heart that is receiving high doses. The aforementioned risk in cardiac dose should therefore be considered as part of the treatment process.
References: [1] Stewart JR, Fajardo LF. Radiation-induced heart disease: An update. Prog Cardiovasc Dis 1984; 27:173- 194. [2] Schultz-Hector S, Klaus-Rudiger Trott. Radiation-Induced Cardiovascular Diseases:Is the Epidemiologic Evidence compatible with the Radiobiologic Data? Int J Radio Biol Phys 2007; 67: 10-18. [3] Carr ZA, Land CE et al. Coronary Heart Disease after Radiotherapy for Peptic Ulcer Disease. Int J Radiat Oncol Biol Phys 2005; 61: 842-850. [4] Huddart RA, Norman A, Shahidi M et al. Cardiovascular Disease as a long-term complication of treatment for Testicular cancer. J Clin Oncol 2003; 21: 1513-1523. [5] Darby SC, Ewertz M, et al. Risk of Ischemic Heart Disease in Women after Radiotherapy for Breast Cancer. The New England Journal of Medicine 2013; 368: 987.
31. The introduction of a new electrical technology in Scotland Smith D N University of Edinburgh email: [email protected] Background: In 1743 Archbald Spens, a Scottish doctor and science lecturer, gave a demonstration of electricity in Boston, Massachusetts to an audience which included Benjamin Franklin. The discovery in Leyden of the charge storing properties of a jar of water made the front pages of the Scottish press in April 1746 [3]. The following March these same papers advertised a course of experiments on electricity by Dr Young, an army surgeon, for the benefit of the Royal Infirmary of Edinburgh [2]. Later in January 1750 Dr John Rutherford (Professor of the Institutes of Medicine) began a series of clinical trials of electricity within the Infirmary for the treatment of patients with a variety of conditions [5].
Method: This study has used contemporary sources to establish the knowledge of electricity available in mid-eighteenth century Scotland; to determine the type of treatments given and their outcome; and to follow the subsequent applications of this new technique. The newspapers and periodicals of the time give details of public lectures and of significant electrical discoveries in Britain, the American Colonies and in Continental Europe. Student notes of Rutherford’s clinical lectures recorded over a period of about five years contain details of relevant cases and their outcomes [5]. The records of the Managers of the Royal Infirmary and of its Treasurer record the special provisions that were made for the installation and use of this innovative technique [4].
Results: In the first quarter of the 18th century many Scottish medical students first undertook an arts course, including natural philosophy, at a university in the home country before attending continental universities in order to obtain their doctorate. Rutherford studied under Edinburgh’s first Professor of Natural Philosophy (Robert Steuart) [1] before attending medical classes in Leyden and graduating MD in Rheims. Rutherford would have heard of early attempts at electrical treatment and in 1750 he borrowed a machine to make his own trial [6]. Four months later he purchased and presented an electrical machine to the Infirmary and had at least one notable success widely reported in the press [7]. The machine was so important to the managers that they ordered a special room to be partitioned off and fitted with a locked door. In the following years they provided for the repair, maintenance and operation of the machine [4]. Then in 1771 the managers readily acceded to a request by William Cullen for the purchase of a more portable machine. In the meantime electrical treatments were being given to patients in the Borders [8]. The Edinburgh Public Dispensary made such treatments generally available to the community from 1778.
Conclusions: The use of electricity as a treatment preceded the invention of the stethoscope by over 40 years and was the first modern technology to be introduced systematically into health care. It has remained at the heart of medicine ever since. The machines used by Rutherford, Cullen and their contemporaries contained a charge generator, a charge storage device and a means of delivering that stored charge to a patient. More recent developments may have taken medical electricity in many other directions but every defibrillator has these same three essential parts in a modern form.
Key References: [1].A Short Account of the University of Edinburgh. Scots Mag., 1741: 3: 371-374 [2] Caledonian Mercury, 1747: 4125 (19 March). [3] Edinburgh Evening Courant, 1746: 7776 (1 April). [4] Experiments on Electricity. Gen. Mag., 1745: 15: 193-197 [5] RIE Managers’ Minutes, 1749-60: 3: 7 May 1750. LHB Archive, EU Lib. Spec. Coll. [6] Rutherford J. Clinical Lectures. 1749-53: EU Lib. Spec. Coll. Manuscripts [7] Watts W. Cure by Electricity. Gen. Mag., 1751: 21:152 [8] Whytt, R. Phil. Trans. (1758) V. 50 pp383-395.
32. Cluster analysis of high dimensionality chromosomal data following treatment of uveal melanoma 1Caines R, 1Eleuteri 2A, Kalirai H, 1Fisher A, 3Heimann H, 3Damato B, 2Coupland S, 1Taktak A 1Department of Medical Physics and Clinical Engineering, Royal Liverpool University Hospital, UK. 2Department of Ophthalmology, Royal Liverpool University Hospital, UK. 3Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK. email: [email protected] Purpose: To investigate any underlying correlations in multiple ligation-dependent probe amplification (MLPA) data and their significance on survival following treatment of uveal melanoma (UM).
Methods: MLPA data were available for 31 loci across 4 chromosomes (1p, 3, 6 and 8) from tumour material obtained from 602 UM patients treated at the Liverpool Ocular Oncology Centre (LOOC) between 1998 and 2012 (Lake et al., 2011). In this study, data representing chromosomes 3 and 8 were analysed in depth as their association with UM patient survival is well-known (Damato et al., 2010). K-means cluster analysis was performed on these data to detect any latent structure in the dataset (Semlow, 2009). Principal Component Analysis (PCA) was also undertaken to reduce the dimensionality of the data whilst maximising the variance. Survival analyses of identified clusters were performed using Kaplan-Meier and log-rank statistical tests.
Results: Cluster analysis revealed the presence of 3 distinct prognostic groups corresponding to: 1) normal chromosome 3 and chromosome 8 data; 2) chromosome 3 deletion and chromosome 8 gain; and 3) either chromosome 3 deletion or chromosome 8 gain. Threshold values of 0.85 for deletion and 1.15 for gain optimized classification of the clusters (p < 0.001, Mann-Whitney test). Kaplan –Meier analysis showed 5- year survival figures of approximately 90%, 20% and 70% for these clusters respectively (p < 0.01, log-rank test). There was strong correlation with tumour size and cellularity.
Conclusions: The study shows that there are three clear clusters in the data based on MLPA chromosomes 3 and 8; 1) with chromosome 3 deletion and normal chromosome 8, 2) with normal chromosome 3 and chromosome 8 gain and 3) with either chromosome 3 or chromosome 8 gain. There was strong evidence of significant correlation between all probes belonging to the same chromosome so there was no evidence for a “signature” gene. There was also strong evidence of significant correlation with tumour size which may act as a confounder.
References: DAMATO, B., DOPIERALA, J. A. & COUPLAND, S. E. 2010. Genotypic profiling of 452 choroidal melanomas with multiplex ligation-dependent probe amplification. Clin Cancer Res, 16, 6083-92. LAKE, S. L., DAMATO, B. E., DOPIERALA, J., BAUDO, M. M., TAKTAK, A. F. & COUPLAND, S. E. 2011. Multiplex ligation-dependent probe amplification analysis of uveal melanoma with extraocular extension demonstrates heterogeneity of gross chromosomal abnormalities. Invest Ophthalmol Vis Sci, 52, 5559-64. SEMLOW, J. L. 2009. Classification I: Linear discriminant analysis and support vector machines Biosignal and Medical Image Processing. Boca Raton, FL: CRC Press.
33. A Process for Approaching the Streamlining of Patient Specific QA for IMRT & VMAT Treatments 1Vinall A, 1Williams A, 2 McDermott S, 1Holmes-Smith W, 1Willis D, 1Currie V, 1Verschoor G 1Dept of Radiotherapy Physics, Norfolk & Norwich University NHSFT, UK. 2UPMC Whitfield Cancer Centre, Waterford, Ireland email: [email protected] Background. In Autumn 2012 the Prime Minister pledged that all patients would have access to advanced radiotherapy, namely IMRT or VMAT treatments. This led to the investment of £23m through the Radiotherapy Innovation Fund (1). The demand for increased numbers of patients to be treated with IMRT/VMAT is likely to increase still further over coming years (2). For our Department the development of this increase was hampered by lack of machine capacity for patient specific QA associated with these types of treatments. The Department already treats extended hours (8am-8pm on weekdays).The argument for no longer carrying out patient QA on a treatment technique once QA has been performed on at least 10 patients is arguably flawed in the case of treatment techniques such as VMAT or IMRT where complex radiation fluence patterns are delivered. Equally the argument for carrying out QA on 1 in 10 patients or once a month does not give confidence that the remaining 9 patients received the correct treatment. The Department in Norwich therefore embarked on a process for reducing the amount of patient specific QA requiring linac time, on a logical and considered basis. Methods. The Department reviewed all the major radiotherapy accidents that had occurred in the previous few years and assessed which QA processes available within our Department might have prevented a similar accident occurring at our centre. The Department also considered, for different treatment techniques, what errors might be possible and which of our available QA resources would highlight each of those errors. Whilst this was not an exhaustive list, it sought to capture the main sources of error. Included amongst the QA processes available, the Department has developed a technique using the commercially available Monitor Unit software IMSure to create a virtual 2D array (this work has been presented elsewhere (3)). Results. Tables of the radiotherapy errors and QA systems available within the Department against each of the Department’s treatment techniques have been produced. From these it can be seen that there are QA systems in place which should prevent a major treatment error. The Department has a long history of diode use for patient in-vivo QA and this has been in routine use for both IMRT and some VMAT treatments for a number of years. The use of diodes for VMAT is one of the factors that has contributed to streamlining the patient QA process. Discussion. The QA processes being carried out for each treatment technique were assessed, what information each one gave, and whether any could safely be removed from the pathway process without compromising patient safety. As a result of this exercise the decision was taken to stop individual linac based patient QA for all ‘prostate with seminal vesicle’ patients. For these patients a single arc VMAT treatment with relatively unmodulated fields is the normal treatment delivery, with treatment plans based on a class solution. QA is carried out using IMSure, with diodes on the first fraction. For ‘simple’ IMRT patients the linac based QA has been replaced with the virtual 2D array process. As these represent a significant number of VMAT and IMRT patients this has resulted in a large reduction in the time required for linac based patient specific QA and has led to an increase in the number of patients to whom we can offer IMRT or VMAT treatments. Conclusion. It is possible to achieve reduction of patient specific QA for advanced radiotherapy treatments by careful assessment of the potential errors and the ability of a Department’s QA devices to ‘catch’ those errors. As a result, according to NatCanSat data, this department has increased its VMAT patient throughput on a consistent basis such that it is now regularly delivering over 40% of radical patients with IMRT/VMAT despite its linacs being amongst the busiest in the country. Key references. (1)The Radiotherapy Innovation Fund: an evaluation of the Prime Minister’s £23 million fund, CRUK, July 2013 (2) Vision for Radiotherapy 2014-2024, CRUK/NHS England , March 2014 (3) Williams, A 2012 “IMRT Patient Specific QA – without a linac” IPEM Conference Presentation, IMRT Verification: making the most of it
34. Commissioning the first RayStation Treatment Planning System in the UK 1Waldron J, 1Mason S 1Medical Physics, Ninewells Hospital, Dundee, DD1 9SY, UK. email: [email protected] Background. RayStation is a commercial radiotherapy Treatment Planning System (TPS) developed by RaySearch Laboratories (Sweden). The radiotherapy department in Ninewells Hospital in Dundee is the first in the UK to install this system. This presentation outlines and assesses the commissioning process followed. Methods. The beam qualities delivered by each linear accelerator in our centre were modelled first. An extensive set of water tank data, including Percentage Depth Doses (PDDs) and beam profiles, was imported into the provided RayPhysics beam commissioning software. An auto-modeling process was run, and then the beam model parameters were manually altered until an acceptable agreement between the measured and computed curves was reached. The model accuracy was then verified by a thorough comparison with our previous TPS – Oncentra MasterPlan (OMP, Elekta, Sweden). The dose distributions in a homogeneous phantom from a number of different basic field shapes were compared. The dosimetric differences between the two systems were then quantified for a number of clinical treatment plans of different sites. This was of critical importance in lung treatments especially because RayStation only offers the Collapsed Cone (CC) dose calculation algorithm and the clinical experience for lung treatments in our centre is based on the OMP Pencil Beam (PB) algorithm. Results. On average the modelled and measured PDDs agreed within 0.5% in the fall-off region. The in- field region of the dose profiles agreed on average within 1.5%. Worse agreement was seen in the PDD build-up and the profile penumbra and out-of-field regions, though it is accepted that the model does not perform well in these regions. Good agreement between RayStation and OMP was found for basic field shapes. Dose differences were generally well within 3% except for a small number of extreme cases such as very large fields. A number of significant differences between the two systems were seen in the clinical plans, particularly when comparing PB to CC. Discussion. Commissioning the beam models was found to be a time consuming process. There are no previous published guidelines on the accuracy achievable in the RayPhysics commissioning module. The dose distributions of basic field shapes in RayStation were found to agree well with OMP despite some basic differences in the dose calculation method. The lack of a PB calculation in RayStation has forced our centre to move to CC for all treatments. Conclusion. The RayStation TPS has been successfully commissioned in our centre. We have established what level of accuracy can be achieved in beam modeling.
35. Measuring the tube leakage on two Varian TrueBeam Linear Accelerators 1Whitehead E, 1Jupp T, 1So C, 1Hollaway P, 1Pryor M 1Regional Radiation Protection Service, Royal Surrey County Hospital, UK. email: [email protected] Abstract. The aim of this work was to measure the leakage from the tube head on two Varian TrueBeam linear accelerators following their installation into a new Radiotherapy centre. Initially the tube heads were covered in enveloped wrapped x-ray film in order to visually identify where there were higher areas of tube leakage. The collimator jaws were closed to their limit of a 0.5cm field. The linac was run at 15MV with a dose rate of 600MU/min for two minutes. The x-ray films were subsequently processed and used to produce a leakage map and the results indicate a similar leakage pattern on both linacs. The areas of highest leakage indicated were the on the top of the linac head, through the target end and at points around the collimator housing. Dose rate measurements were then taken at the points indicated by the leakage pattern maps with a 180cc ion chamber and with and without build-up material. Dose rate measurements were also taken at cardinal points at one meter from the linac head housing due to the focal position not being accurately known. The specification for leakage from a linac head is less than 0.1% of the primary beam dose rate at one meter from the linac housing. Our measurements indicate that the point of maximum leakage was at the top of the linac head and that this corresponded to 0.04% of the primary axis dose rate, based on a calibration of 1 cGy per MU. This is felt to be one of the last opportunities to use film to assess areas of leakage as film processing facilities are being removed. The leakage map for this model can be used as a basis for future surveys of similar equipment.
INDEX OF PRESENTING AUTHORS
A H
Abuhaimed A ...... 12 Hall Barrientos P ...... 29 Agnew CE ...... 55 Hall R ...... 80 Akinluyi E ...... 20, 21 Hand A ...... 73 Al Sa’d M ...... 88 Hart D ...... 47, 59 Allen J ...... 32, 46 Hart R ...... 72 Amoore J N ...... 4, 22, 89, 90 Hartley A ...... 100 Awwad A ...... 25 Hilton K ...... 16 Ayers M ...... 60 Hoffmans-Holtzer NA ...... 70 Hutchinson K ...... 101 B I Beavis A W ...... 11, 14 Bedford J ...... 72, 91 Inglis S ...... 35 Bertha C ...... 69 Biggar R ...... 18 Billas I ...... 92 J Black R A ...... 75 Brennan D ...... 7 Jarritt P...... 37 Browne J E...... 33 Ju X ...... 62 Burke P ...... 51 Jun L ...... 36 Byrne J ...... 68
K C Kamali-Zonouzi P ...... 103 Choi O-C ...... 41, 42 Kanakavelu N...... 28 Clifton D A ...... 32 Keating D ...... 37, 54 Cooke G ...... 93 Keevil S ...... 67 Coomber H ...... 93 Keiller D ...... 83 Cosgriff PS ...... 20 King L R ...... 52 Cournane S ...... 34, 51, 94, 102
L D Lannon C ...... 103 Davie A ...... 95 Lea R ...... 104 Dekker A...... 77 Lee P ...... 6 Dewhurst J M ...... 73 Leydon P ...... 27 Di Maria C ...... 96 Dixon B J ...... 97 Dixon M ...... 53 M Doran S ...... 78 Drake D ...... 13 Duffy M ...... 45 Magee JS ...... 15 Mahabadi S ...... 48 Marsden S P ...... 47, 49 E Matthews P M ...... 67 Mayles P ...... 71 McCarthy J P ...... 3 East R ...... 59 McComb C ...... 23 Eaton D J ...... 99 McGarry CK ...... 57 Edyvean S ...... 50 McWilliam A ...... 105 Menon R ...... 106 Moloney S ...... 106, 107 F Moore C S ...... 66 Moore R ...... 55 Fagan A J ...... 24 Moran A M ...... 81 Fathi K ...... 99 Moran L ...... 31 N Smith D N ...... 112 Speight R ...... 38, 40 Sutton D G ...... 76 Naisbit M ...... 74 Swift C ...... 6 Nash D ...... 56 Ntentas G ...... 30 T O Tahir BA ...... 39 Taktak A...... 113 O’Neill J ...... 108 Tarbert C M ...... 61 Oommen K ...... 109 Taylor J C ...... 79 Thwaites D I ...... 38, 58, 86 Turner C...... 44 P Tyler J M ...... 83
Palmer A L ...... 27 Parvin EM...... 9 V Patel M ...... 5, 77 Pearson D ...... 54 Vinall A ...... 10, 114 Perring S ...... 63 Priba L ...... 30, 65 W R Waldron J ...... 115 Walker A ...... 7 Richmond N ...... 69 Walker EP ...... 17 Riddick J ...... 43 Webster G ...... 79 Robertson D ...... 87 Welsh D ...... 44 Robinson M ...... 64 Whitehead E...... 115 Wilkins H ...... 85 Willett A ...... 19 S Worrall M ...... 63, 76 Wyper D ...... 3 Salem H ...... 110 Scott J R ...... 111 Simmons A ...... 84 Y Skikiewicz M ...... 81 Small A ...... 82, 111 Young J ...... 9