Effectiveness of Adjusting Radiographic Technique Parameters on Image Quality in Direct Digital Radiography: a Systematic Review Protocol

SYSTEMATIC REVIEW PROTOCOL

Effectiveness of adjusting radiographic technique parameters on image quality in direct digital radiography: a systematic review protocol

1,2 3 2,4 2 Caitlin Steffensen Gregory Trypis Gordon T.W. Mander Zachary Munn

1Philips Australia and New Zealand, Murrarie, Australia, 2Joanna Briggs Institute, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, Australia, 3Department of Medical Imaging, Sunshine Coast University Hospital, Birtinya, Australia, and 4Department of Medical Imaging, Toowoomba Hospital, Toowoomba, Australia

ABSTRACT

Objective: The purpose of this review is to investigate the effectiveness of adjusting radiographic technique parameters on image quality of projectional radiographs acquired on a direct digital radiography system. Introduction: Projectional radiography performed with direct digital detectors is now commonplace in many medical imaging departments across the world. While the acquisition technology has advanced, it appears that many sites have not optimized their radiographic technique factors for this new technology. The aim of this review is to uncover evidence to support the continued use of these traditional technique parameters or to suggest changes in clinical practice that would produce optimized results. Inclusion criteria: The review will consider studies that include projectional radiographs acquired on a direct digital radiography system of the axial and appendicular skeleton. Only studies that investigate a human subject (living or post-mortem), or an anthropomorphic phantom will be included. Studies that directly investigate the effect of changing a technique parameter on the resultant image quality and the effect on patient dose will be included. Methods: A comprehensive search of both published and unpublished literature will be performed to uncover studies meeting the inclusion criteria. Studies will be screened for inclusion by two reviewers and disagreements resolved through discussion or with a third reviewer. Studies included in final analysis will be critically appraised for methodological quality. Data will be extracted by a single reviewer and checked by the author team for accuracy. Statistical meta-analysis and subgroup analyses will be performed as appropriate, and a Summary of Findings created. Systematic review registration number: PROSPERO CRD42019137806 Keywords Direct digital radiography; image quality; optimization; radiographic technique JBI Database System Rev Implement Rep 2019; 17(10):2165–2173.

Introduction image acquisition has shifted from an analog process 3 ver the past 122 years since the discovery of to a digital one. The way projectional radiographs O x-rays, diagnostic imaging has undergone signifi- are acquired, manipulated, stored and viewed has cant evolution.1,2 During this time, the method of advanced, leading to significant changes for all stake- holders.4 Images are now able to be viewed simulta- Correspondence: Caitlin Steffensen, neously by multiple viewers across differing geographic [email protected] locations and stored for almost instantaneous 3 Conflicts of interest: Primary author, CS, is an employee of Philips retrieval. What has remained constant since the incep- Australia and New Zealand. This review will not evaluate the perfor- tion of diagnostic x-ray imaging is the need for appro- mance of different image processing software. It will extract details on priate image quality to provide an accurate diagnosis. detector material for the sole purpose of providing accurate technique The literature acknowledges that dose and image information for the specific detector type (should there be any varia- 5,6 tion dependent on detector material). There will be no ranking/grading quality are directly related. Image quality can be of performance. The other authors declare no conflicts of interest. significantly improved by increasing the exposure DOI: 10.11124/JBISRIR-2017-003888 factors, but this is at the expense of increased

JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2165

radiation dose to the patient.7 Optimization, rather In terms of acquisition, DDR detectors have a than maximization, of image quality in diagnostic wider dynamic range than that of film-screen. The radiography should be the chief goal. An optimized dynamic range, also known as latitude, of an acqui- technique results in the clinical question being effec- sition device refers to the range of exposure values tively answered, while not imposing a radiation dose over which it is able to produce an adequate image.13 to the patient that is higher than necessary.8 By Direct digital radiography detectors do not require utilizing an optimized technique, radiographers are tight control of exposure factors in order to produce able to ensure that their commitment to keeping an image of diagnostic quality, as was the case in film doses ‘‘as low as reasonably achievable’’ is met, imaging, due to their wide dynamic range.12 Another while not compromising the diagnostic quality of advantage of the wide dynamic range of the DDR the examination. detector is their ability to represent structures of In the literature, digital radiography is used as an varying attenuation in a single image.3 In terms of umbrella term for images that are acquired through image display, digital radiography images are able to any mechanism that transforms the incident photon be manipulated after their creation by way of post- into an electrical charge.9 Under this definition, processing. Optimal contrast and brightness is no digital radiography is comprised of both computed longer reliant on the use of a specific film-screen radiography (CR) and direct digital radiography combination or set of radiographic technique (DDR).3 Direct digital radiography systems acquire parameters.10 images by converting the incident x-ray energy into a Digital radiography technology has given rise to digital signal almost instantaneously,6 skipping the many avenues for dose reduction; no longer bound intermediary storage step that is associated with by a certain exposure requirement for optimal image CR.10 The detector used in DDR systems acts as quality, the new limiting factor is image noise.14,15 both the acquisition and conversion device, whereas a There are a number of sources that are responsible CR system has a separate acquisition device (the for image noise,16 yet regardless of its origin, all photostimulable phosphor plate) and conversion noise leads to degradation of image quality. Noise is device (the processor). In a DDR system, the mecha- the result of statistical fluctuations in signal intensity nism by which the energy is transformed into a digital received by the detector, and is represented in the signal depends on the type of detector used, and this is resultant image as fluctuations in brightness, leading the method by which DDR systems are classified.3 to a mottled appearance.5,17 Visual appreciation of This review will focus only on the optimization of image noise is very subjective18 and what constitutes radiographic technique parameters for DDR. an acceptable level of noise depends on both the Common across all imaging modalities, not just preference of the observer and on the clinical ques- DDR, is the need for appropriate image quality for tion being asked.12,19 diagnosis. When considering the term ‘‘image qual- Image quality research in medical imaging is ity’’, it is important to make the distinction between performed using a variety of methods, one or a a visually appealing image and an image of adequate combination of test objects, phantoms, and clinically quality. An image of ‘‘adequate’’ quality can effec- acquired images.7 Test objects measure a specific tively answer the clinical question posed,7 regardless quality of an imaging system under ideal conditions, of whether the image is visually appealing to the but it is difficult to link these results to performance reader or not. Adequate image quality in analog in clinical use.7 Imaging phantoms used for research imaging revolved around obtaining images with fall into one of two broad categories: geometric or optimal contrast and density.4 Image contrast and anthropomorphic. Geometric phantoms consist pri- density were almost solely dependent on exposure marily of geometric shapes, whereas anthropomor- technique and film-screen combination factors cho- phic phantoms are designed to be analogous to sen prior to acquisition.11,12 As the radiographic film human tissue and accurately represent the anatomi- acted as both the acquisition and display medium, cal structure of the body.20 As images of test objects there were limited means of altering the image alone are unable to be directly linked to clinical appearance after exposure.10 The transition from performance,7 only studies using phantoms and/or analog to digital imaging saw the decoupling of clinically acquired images will be included for the acquisition and display mediums.4 this review.

JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2166

Subjective and objective measures of image qual- Reviews and Implementation Reports, and the ity exist, summarized well in Martin et al.7 Subjec- Cochrane Database of Systematic Reviews shows tive measures of image quality, such as visual that there have been no systematic reviews on opti- grading analysis, performed on clinical images by mizing image quality for DDR. This systematic appropriately credentialed individuals are useful as review will synthesize available evidence to highlight they allow more direct assessment of clinical utility areas for improvement upon currently accepted best of the resultant image.21,22 The most common objec- practice, as well as establish gaps in the literature tive measure of image quality is the signal to noise deserving of further investigation. ratio, which describes the strength of a signal in the 23 presence of background noise. For the purpose of Review question this review, any method of image quality evaluation will be considered, provided that it is applied in an What is the effectiveness of adjusting radiographic appropriate context. technique parameters on image quality in projec- There are five radiographic technique parameters tional radiographs acquired on a DDR system? available to be manipulated at the time of image acquisition. These are exposure factors (tube cur- Inclusion criteria rent time product and tube voltage), source-to- Participants image distance, a choice of additional beam filtra- The review will consider studies that include projec- tion and a method of scatter reduction. The applied tional radiographs acquired on a DDR system of the tube voltage directly controls the peak energy of the axial and appendicular skeleton. Projectional radio- x-ray beam which is described by kilovoltage graphs of phantoms, adult or pediatric patients (kV).24 The current applied to the x-ray tube and (living or post-mortem) will be considered. Studies the length of time the current is applied for are using test objects, such as contrast-detail phantoms, described by milliampere-seconds (mAs).24 Addi- to assess detector characteristics in the absence of tional beam filtration is used to remove low energy application to a specific clinical scenario will be photons, and this acts on top of the inherent filtra- excluded from review. tion within the tube housing. It is used to reduce the number of photons that would have sufficient Interventions energy to reach the patient, but insufficient energy This review will consider studies that evaluate the to add to the diagnostic image, therefore adding effect of changing any, all, or a combination of the only to the overall patient dose.24 Source-to-image following radiographic technique parameters: distance is the distance between the x-ray source and i. Tube voltage within a clinically applicable the image receptor.2 Scattered radiation, which range: 40–150 kV degrades image quality, can be compensated for ii. Tube current time product within a clinically by use of either an air-gap technique or an anti- applicable range: 0.1–200 mAs scatter grid.11 Manipulation of each of these param- iii. Additional beam filtration of copper (Cu) or eters has a direct impact on patient dose, and on aluminum (Al) in differing thicknesses resultant image quality. Traditional selection of iv. Source-to-image receptor distance within a clin- technique parameters is due to a combination of ically applicable range: >100 cm governing body recommendations, manufacturer v. Use of anti-scatter grid, with a clinically accept- recommendations, and of the personal experience able ratio of 8:1-12:1, or air-gap technique. of the performing radiographer.25 Optimization of radiographic technique parame- Comparators ters for improved image quality is a key concern in Evaluations of different ranges or options for each the pursuit of providing high-level patient care. radiographic technique parameter will be compared. While the image acquisition technology has evolved Studies need to directly compare either an optimized and continues to advance, it is evident that limited technique to a currently accepted standardized work has been conducted to optimize technique technique, or at least two different options for parameters to suit this new technology.4 To date, optimization of a particular technique parameter a search of PubMed, JBI Database of Systematic to be included.

JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2167

Outcomes The search for unpublished studies will include: This review will consider studies that include the ProQuest Repository for Masters and PhD theses. A following outcomes: evaluation of image quality and search in Google Scholar of selected keywords and patient dose. results from the first 10 pages will be reviewed. Image quality will be evaluated by subjective means; objective evaluation will be included but Study selection only in studies that also include subjective evalua- Following the search, all identified citations will be tion. Subjective image quality evaluation should be collated and uploaded into EndNote X8 (Clarivate performed by individuals appropriately credentialed Analytics, PA, USA) and duplicates removed. Titles to make comment or report on diagnostic images. and abstracts will then be screened by two indepen- Patient dose will be considered also to ensure that the dent reviewers (CS & GM) for assessment against technique is optimized, but only in studies that also the inclusion criteria for the review. Studies that may measure image quality. meet the inclusion criteria will be retrieved in full and their details imported into JBI System for the Types of studies Unified Management, Assessment and Review of This review will consider all experimental and quasi- Information (JBI SUMARI; Joanna Briggs Institute, experimental study designs including (but not lim- Adelaide, Australia). The full text of selected studies ited to) randomized controlled trials, non-random- will be retrieved and assessed in detail against the ized controlled trials, before and after studies and inclusion criteria. Full-text studies that do not meet interrupted time-series studies that meet our inclu- the inclusion criteria will be excluded and reasons sion criteria. In addition, analytical observational for exclusion will be provided in an appendix in the studies including prospective and retrospective final systematic review report. Included studies will cohort studies, case-control studies and analytical undergo a process of critical appraisal. The results of cross-sectional studies will be considered for inclu- the search will be reported in full in the final report sion. This review will also consider descriptive obser- and presented in a Preferred Reporting Items for vational study designs including case series, Systematic Reviews and Meta-Analyses (PRISMA) individual case reports and descriptive cross-sec- flow diagram.26 Any disagreements that arise tional studies for inclusion. Studies published in between the reviewers will be resolved through dis- English will be included. Studies published from cussion, or with a third reviewer. 1997 will be included, as the first digital flat panel detector was released for use in this year.15 Assessment of methodological quality Selected studies will be critically appraised by two Methods independent reviewers (CS & GM) at the study level Search strategy for methodological quality in the review using a The search strategy will aim to find both published tailored critical appraisal instrument available for and unpublished studies. An initial limited search of review in Appendix II. Any disagreements that arise PubMed and Embase has been undertaken followed will be resolved through discussion or with a third by analysis of the text words contained in the title and reviewer. abstract, and of the index terms used to describe All studies, regardless of their methodological article. This informed the development of a search quality, will undergo data extraction and synthesis strategy which will be tailored for each information (where possible). source. A full search strategy for PubMed is detailed in Appendix I. The reference list of all studies selected for Data extraction critical appraisal will be screened for additional stud- Data will be extracted from papers included in the ies. Authors of included studies will also be contacted review using a tailored extraction tool available in to obtain details of other studies worthy of inclusion. Appendix III by the first author and checked by the author team for accuracy. The data extracted Information sources will include specific details about the radiographic The databases to be searched include: PubMed, technique parameters investigated, method of Embase, Scopus and CINAHL. image quality evaluation, types of examinations

JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2168

investigated, subject used for the investigation (geo- of Findings will present a ranking of the quality of metric phantom, anthropomorphic phantom, post- the evidence based on study limitations (risk of bias), mortem subject, or evaluation of clinically acquired indirectness, inconsistency, imprecision and publica- images), and type of DDR detector used and the tion bias. The following outcomes will be included in results for image quality. Any disagreements that the Summary of Findings: subjective image quality, arise between the reviewers will be resolved through objective image quality and patient dose. discussion. Authors of papers will be contacted to request missing or additional data where required. Acknowledgments This review protocol contributes to the partial ful- Data synthesis filment of the requirements of the Master of Clinical Papers will, where possible, be pooled in statistical Science degree program for author CS awarded by meta-analysis using OpenMeta [Analyst]. For head- The University of Adelaide in conjunction with JBI. to-head comparisons, effect sizes will be expressed This program was funded by the Australian Govern- as either odds ratios (for dichotomous data) or ment through an Australian Government Research weighted (or standardized) mean differences (for Training Program (RTP) Scholarship. continuous data), and their 95% confidence inter- The authors would also like to acknowledge vals will be calculated for analysis. Heterogeneity Mr Michael Neep for his guidance and comments. will be assessed statistically using the standard chi- squared and I-squared tests. The choice of model (random or fixed effects) and method for meta- References analysis will be based on the guidance by Tufanaru 1. Hessenbruch A. A brief history of x-rays. Endeavour 2002; 26(4):137–41. et al.27 OpenMeta [Analyst] will be used for single 2. Bontrager KL, Lampignano JP. Bontrager’s Handbook of group analyses of continuous variables using Radiographic Positioning and Techniques. 7th ed. St. Louis, means and for single group analyses of dichoto- MO: Mosby/Elsevier; 2010. mous variables using a Freeman-Tukey transforma- 3. Ko¨rner M, Weber CH, Wirth S, Pfeifer K-J, Reiser MF, Treitl M. tion. Advances in Digital Radiography: Physical Principles and Subgroup analyses will be conducted where there System Overview. Radiographics 2007;27(3):675–86. are sufficient data to investigate specific ranges of 4. Samei E Dobbins IIIJT, Lo JY, Tornai MP. A framework for radiographic technique parameters for adult and optimising the radiographic technique in digital X-ray paediatric populations, for specific examinations imaging. Radiat Prot Dosim 2005;114(1–3):220–9. of discrete body regions. Sensitivity analyses will 5. Smith NB, Webb A. Introduction to Medical Imaging Physics, be conducted to test decisions made regarding our Engineering and Clinical Applications. Cambridge: Cam- bridge University Press; 2011. analytical approach and our assumptions regarding 6. Suetens P. Fundamentals of Medical Imaging. Cambridge: the grouping of similar data where uncertainty Cambridge University Press; 2009. arises. 7. Martin CJ, Sharp PF, Sutton DG. Measurement of image A funnel plot will be generated to assess publica- quality in diagnostic radiology. Appl Radiat Isot 1999; tion bias if there are 10 or more studies included in a 50(1):21–38. meta-analysis. Statistical tests for funnel plot asym- 8. Bushberg JT, Seibert JA, Leidholdt EM. The Essential Physics metry (Egger test, Begg test, Harbord test) will be of Medical Imaging. 3rd ed. Philadelphia, PA: Wolters Kluwer performed where appropriate. Health/Lippincott Williams & Wilkins; 2012. 9. Cruz R. Digital radiography, image archiving and image Assessing certainty in the findings display: Practical tips. Can Vet J 2008;49(11):1122–3. A Summary of Findings will be created using 10. Bansal GJ. Digital radiography. A comparison with modern conventional imaging. Postgrad Med J 2006;82(969): GRADEpro software (McMaster University, ON, 425–8. Canada). As no formal Grading of Recommenda- 11. Ritenour ER. Physics overview of screen-film radiography. tions Assessment, Development and Evaluation Radiographics 1996;16(4):903–16. (GRADE) approach exists currently for these types 12. Martin CJ. Optimisation in general radiography. Biomed of reviews, we will try to align our judgment of Imaging Interv J 2007;3(2):e18. certainty in the results to the GRADE principles 13. Sprawls P. Physical Principles of Medical Imaging. 2nd ed. while tailoring to this type of review. The Summary Madison, WI: Medical Physics Publishing; 1995.

JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2169

14. Tapiovaara MJ, Sandborg M, Dance DR. A search for 21. Dobbins J. Image Quality Metrics for Digital Systems, SPIE improved technique factors in paediatric fluoroscopy. Phys Press, 2000. Med Biol 1999;44(2):537–59. 22. Sharp P, Barber DC, Brown DG, Burgess AE, Metz CE, Myers 15. Neitzel U. Status and prospects of digital detector technol- KJ, et al. Report 54. Reports of the International Commission ogy for CR and DR. Radiat Prot Dosim 2005;114(1–3):32–8. on Radiation Units and Measurements 1996; os28(1): 1-5. 16. Lanc¸a L, Silva A. Image Quality in Diagnostic Radiology. 23. Huda W, Abrahams RB. Radiographic Techniques, Contrast, Digital Imaging Systems for Plain Radiography. New York, and Noise in X-Ray Imaging. Am J Roentgenol 2015; NY: Springer New York; 2013; pp. 63–77. 204(2):W126–31. 17. Lancaster JL, Hasegawa BH. Fundamental mathematics and 24. Holmes K, Clark KC, Elkington M, Harris P. Clark’s Essential physics of medical imaging, Boca Raton, FL: Boca Raton, FL: Physics in Imaging for Radiographers. Boca Raton, FL: CRC CRC Press, Taylor & Francis Group, 2016. Press, Taylor & Francis Group; 2014. 18. Uffmann M, Schaefer-Prokop C. Digital radiography: The 25. Jones A, Ansell C, Jerrom C, Honey ID. Optimization of balance between image quality and required radiation image quality and patient dose in radiographs of paediatric dose. Eur J Radiol; 72(2): 202–208. extremities using direct digital radiography. Br J Radiol 19. Erasmus A. A rabbit phantom study to reduce neonatal 1050;88(1050):20140660. radiation dose without compromising image quality. 26. Moher D, Liberati A, Tetzlaff J, Altman DG. The PRISMA Department of Medical Physics University of the Free State Group. Preferred reporting items for systematic reviews and 2015. p. 126. meta-analyses: the PRISMA Statement. PLoS Med 2009; 20. Henriques LMS, Cerqueira RAD, Santos WS, Pereira AJS, 6(7):e1000097. Rodrigues TMA, Carvalho Ju´nior AB, et al. Characterisation 27. Tufanaru C, Munn Z, Stephenson M, Aromataris E. Fixed or of an anthropomorphic chest phantom for dose random effects meta-analysis? Common methodological measurements in radiology beams. Rad Phys Chem 2014; issues in systematic reviews of effectiveness. Int J Evid 95:296–8. Based Healthc 2015;13(3):196–207.

JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2170

Appendix I: Search strategy for PubMed

Technique Image quality Digital ‘‘kV’’[tw] OR ‘‘Radiographic Image Enhance- ‘‘Digital Radiography’’[tw] OR ‘‘kilovoltage’’[tw] OR ment’’[mh:noexp] OR ‘‘flat panel detector’’[tw] OR ‘‘tube potential’’[tw] OR ‘‘Radiation Dosage’’[mh] OR ‘‘flat-panel detector’’[tw] OR ‘‘tube voltage’’[tw] OR ‘‘Phantoms, Imaging’’[mh] OR ‘‘FPD’’[tw] OR ‘‘mA’’[tw] OR ‘‘Image Quality’’[tw]OR ‘‘direct capture’’[tw] OR ‘‘tube current’’[tw] OR ‘‘optimisation’’[tw] OR ‘‘indirect capture’’[tw] OR ‘‘beam filter’’[tw] OR ‘‘optimization’’[tw]OR ‘‘DR’’[tw] OR ‘‘beam filtration’’[tw] OR ‘‘improvÃ’’[tw] OR ‘‘CCD’’[tw] OR ‘‘SID’’[tw] OR ‘‘CNR’’[tw] OR ‘‘charge coupled device’’[tw] OR ‘‘source-to-image distance’’[tw] ‘‘Contrast-to-noise ratio’’[tw] ‘‘SSD’’[tw] OR OR OR ‘‘solid state detector’’[tw] OR ‘‘source to image distance’’[tw] ‘‘Contrast to noise ratio’’[tw] ‘‘solid-state detector’’[tw] OR ‘‘SNR’’[tw] OR ‘‘Signal-to-noise ratio’’[tw] OR ‘‘Signal to noise ratio’’[tw] OR ‘‘SdNR’’[tw] OR ‘‘Signal difference to noise ratio’’[tw] OR ‘‘Signal-difference-to-noise- ratio’’[tw]

JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2171

Appendix II: Critical appraisal form

Critical Appraisal Checklist for Imaging Studies Reviewer Date

Author Year Record Number

Yes No Unclear Not applicable

1. Was the sample recruited and allocated appropriately?

2. Was the sample studied similar for the study and across groups (if groups are present)?

3. Was the study sample reﬂecve of real world paents/populaons?

4. Were there appropriate measures in place to ensure compliance with protocols to ensure consistent and standard delivery of invesgated technique parameters? 5. Were appropriate measures in place during data collecon and analysis to ensure a consistent and similar or standardised sample? 6. Were there measures in place to ensure imaging equipment is performing at the same speciﬁcaon (within appropriate tolerance) within and (potenally) across imaging equipment?

7. Were outcomes measured in a valid way?

8. Were outcomes measured in a standard and consistent way?

9. Were outcomes measured in a reliable way?

10. Were there comparisons made or was there a control group?

11. Was appropriate stascal analysis used?

Overall appraisal: Include Exclude Seek further info Comments (Including reason for exclusion)

______

JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2172

Appendix III: Data extraction tool

Control technique Optimized technique

Examina- Detectory Detector Outcome Evaluation Pt Pt Study tion Population Participant type material evaluation method kVp mAs Filter Grid SID dose kVp mAs Filter Grid SID dose

kVp: peak kilovoltage; mAs: milliampere-seconds; SID: source-to-image distance

JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2173