Current Day Radiology PACS Systems Perform 2 Basic Functions

Current Day Radiology PACS Systems Perform 2 Basic Functions

Specification for RADIOLOGY PACS

Introduction: The below document describes specifications for a radiology PACS for storage & appropriate display of radiology images (CR/DR, CT, MRI, US, Fluoroscopy, etc). If the same PACS is used for display of other images—ophthalmology, cardiology etc, please ensure standards for storage & display of the types of medical images are reviewed & incorporated into the specification.

Current day Radiology PACS Systems perform 2 basic functions

1. DICOM Image Archive & Manager—i.e. long term store of images—(this can be either provided by a Vendor Neutral Archive or the PACS)

2. DICOM Image Display—display of images stored in the image archive above---This can be either a part of PACS or a separate image viewer.

PACS= DICOM Image Archive/Manager + DICOM Image Display`

PACS integrates with the following IT systems :

PAS (Patient Administration System) for demographics, current location, current responsible consultant/GP

RIS (Radiology Information System) for scheduling information & report information

Modalities—receives images & image related information

1. Demographics & ADT Information consistency—All demographics & ADT (Admission Discharge & Transfer information) must be kept up-to-date on all clinical IT systems within any organization. Any demographics update or patient merges on PAS must realtime update PACS systems.

IHE Standards--Patient Information Reconciliation (PIR) Profile: “PIR handles: unidentified/emergency patient, demographic information updates ( e.g patient name changes (marriage, etc.) , correction of mistakes, ID space mergers). Such changes are reliably propagated to all affected systems, which update all affected data. The result is a complete patient record. “

a)PACS

b)RIS

c)PAS

Must all comply with PIR Profile of IHE.

2. PATIENT BANNER INFORMATION---The patient demographics and ADT information for a patient MUST be consistently displayed on the top demographic banner of any clinical system (PACS, RIS & Ordercomms)---real-time demographics synchronization with PAS is mentioned above. This is hugely important for patient safety & care –ensure that timely communication, ensuring correct ID, timely action can be taken:

  1. Name
  2. DOB
  3. Sex
  4. NHS No.
  5. PAS No.
  6. Current Patient Location
  7. Current Responsible Consultant

3. SEARCH CRITERIA FOR A SINGLE PATIENT or GROUP OF PATIENTS: It should be possible to search for a single/group patients using one or any combination of the following criteria:

  1. Name
  2. DOB
  3. Sex
  4. NHS No.
  5. PAS No.
  6. Current Responsible Consultant
  7. Requesting Responsible Consultant
  8. Current Patient Location
  9. Operator
  10. Reporter
  11. Workflow Status of study (see section--)
  12. Modality
  13. Exam Description
  14. Exam Room
  15. Date or date Range (for exams)

4. CLINICAL DATA FIELDS DISPLAY on Images: Below describes Information that needs to be stored & available for display for the clinical user/Radiologist viewing the PACS image. This also identifies what clinical data fields should be transmitted as metadata fields or tags to XDS registry/repository (if XDS is made the standard for including radiology images into the EPR). The terms used for describing data fields must reflect terms in use in NHS ( e.g.—Responsible Consultant/GP etc)

A. PATIENT DEMOGRAPHICS (synchronized with PAS)

  1. Name,
  2. DOB,
  3. Sex,
  4. PAS No.,
  5. NHS No. (CHI number for Scotland)—NHS number may not be present in 100%exams sent to PACS

B. REQUESTER—synchronized with RIS

  1. Name of Requester
  2. Grade of requester
  3. Contact number of requester
  4. Requesting **Responsible Consultant/GP (Team)—(Also RECIPIENT)
  5. Requesting Speciality/Department/GP surgery
  6. Requesting Institution
  7. Date & time of request made

C. IMAGE DOCUMENT—synchronized with RIS & modalities

  1. Modality
  2. Exam Description---(National Exam Codes & Descriptions)
  3. Date & Time image acquired on modality
  4. Date & time of image sent from modality
  5. Date & time received on PACS
  6. Exam Room (where the exam has been performed)

D. OPERATOR/IMAGE CREATOR –synchronized with RIS & modality

  1. Name of Operator
  2. Grade of Operator
  3. Contact number of Operator
  4. Performing Responsible Consultant
  5. Performing Department/Speciality--Radiology
  6. Performing Institution/NHS Trust

E. REPORTER—synchronized with RIS

  1. Name of Reporter
  2. Grade of reporter
  3. Contact number of reporter
  4. Reporting Responsible Consultant
  5. Reporting Department/Speciality
  6. Reporting Institution/NHS Trust
  7. Date & time report verified

F. WORKFLOW data fields

a. Workflow status

b. Workflow priority

It is important that the relevant data fields are synchronized between PAS, RIS, modalities & PACS.

5. WORKFLOW STATUS: This is a key concept for driving a workflow within the radiology department. The status must be synchronised between Ordercomms, RIS, PACS & Results Acknowledgement systems.

a. Requested (ORDERCOMMS)
b. Request Vetted (RIS)
c. Request held/deferred--with reason (RIS)
d. Scheduled or appointment given (RIS)
e. Cancelled (RIS/ORDERCOMMS) with reason
f. Arrived (RIS)
g. Did Not Attend (RIS)
h. Exam started (RIS)
i. Exam Completed (RIS)
j. Exam not performed --with reason (RIS)
k. Report Dictated (RIS)
l. Unauthorised report (RIS)
m. Authorised/Verified Report(RIS)
n. Amended Report (RIS)
o. Report Viewed (Ordercomms/RAS)
p. Report acknowledged (ORDERCOMMS/RAS)
q. Review requested (Ordercomms)

r. Was not brought (RIS)

s. Housekeeping (RIS)

6. CULLING OF IMAGES

The PACS MUST be able to cull data based on local policies relating to data retention periods. The deletion of culling of exams will be based on patient level retention requirements or exam level retention requirements.

PACS must be hold these 2 data fields

a. Patient level date of deletion

b. Exam Level date of deletion

Whenever there is a mis-match in the date of deletion –patient level & exam level. The later date must be used by the system for culling that image data

For example a simple logic which maybe applied for arriving at the date of culling:

A. Patient level Image Deletion date will be based on

a. 25 years after date of birth

b. 8 years after date of last exam

c. Manual extension to the date of deletion (medico-legal, oncology, research trials etc)

whichever is the later date

B. Image Level Image Deletion date

a. Obstetric exams –after 25years

b. manual extension to date of deletion (slow growing tumour, hip replacement etc).

Whenever there is a mis-match in the date of deletion –patient level & exam level. The later date must be used by the system for culling that image data

A more complex logic-- to include 3 years after date of death maybe included in the logic in Scotland.

The Logic for image deletion maybe applied on any IT system whether ---PACS itself, RIS, PAS or an independent IT system used for applying the logic. Irrespective of the system used to arrive at the date for culling, PACS vendor must be capable of populating & updating the data fields :

a. Patient level date of deletion

b. Exam Level date of deletion

from the IT system that provides these dates.

If PACS itself can provide this logic & record the reason why a deletion date is manually extended. This data (exam level data of deletion & patient level date of deletion) must be migratable at the end of contract.

Please see the DOH guidance on records retention for details.

7. IMAGE RETRIEVAL & DISPLAY PERFORMANCE: Display of images for reporting & comparison should be within 3-5secs on all radiologists workstations. This is a well-accepted clinical standard. Access to images is dependent on server capacity, network, display hardware spec etc. PACS vendor must specify network, server capacity, display hardware appropriately.

However, if we are storing images simply for legal reasons then we need to store them as cheaply as possible---e.g DVDs in a locked cabinet etc. As there is more time available to retrieve images for medico-legal purposes---1-2 weeks. Number of retrievals required for medico-legal reasons will be minute (compared to retrievals required for clinical assessment). We need to inform radiologists & clinical community that images stored are not for clinical usage.

8. DICOM Modality Worklist—When a patient arrives within a department a modality (CT, MR, US etc) needs to be “aware” that the patient is in the department & pull the relevant demographics & study information across to the modality (to avoid manual data entry on the modality). In simplistic terms, DICOM Modality Worklist(DMWL) is a list of patients on RIS who have an “arrived” status. As the scheduling system RIS is responsible for scheduling patients & ensuring logging patients arrival into the department. Each modality will continuously query the RIS (which should provide a DMWL) for any exams –based on modality & Exam Room. Normally the DMWL provider is the scheduling system used for scheduling information to a modality(In Radiology RIS provides a DMWL for radiology modalities). The following information needs to be provided by RIS to modalities.

  1. Patient Demographics
  2. Name,
  3. DOB,
  4. Sex,
  5. PAS No.,
  6. Modality
  7. Exam Description---(usually National/Local Exam Codes & Descriptions)
  8. Exam Room
  9. Accession No. (RIS generates this for every exam)
  10. Study UID (RIS generates this for every exam)

The modalities query the RIS & display a list of patients--- related to one or more Exam rooms who have “arrived” workflow status. Once the status is changed to “exam performed” or “exam not performed” on RIS,-- the exam should drop off the DMWL and no longer be visible to modalities.

Once the exam is completed on the modality, radiographers must be able to send images to PACS.

“IHE Standard—Scheduled Workflow Profile--Scheduled Workflow establishes a seamless flow of information that supports efficient patient care workflow in a typical imaging encounter. It specifies transactions that maintain the consistency of patient information from registration through ordering, scheduling, imaging acquisition, storage and viewing.

Modalities (as acquisition modality actor),

RIS (as departmental system scheduler actor),

PACS (as Image Manager & Image display)

must all support to Scheduled Worklfow Profile of IHE”

A standardised approach to DMWL provision is key to supporting long term storage of DICOM images from non-radiology modalities like—cardiology, retinal images etc

Current Situation in NHS--In many hospitals in NHS, PACS Brokers (often called Connectivity Managers, RIS Gateway, PACS Broker etc) provide DMWL functionality. This could be related to the inability of RIS to provide a DMWL or PACS vendors insist on including brokers as part of their PACS solution. However, if a RIS is capable of providing a DMWL there is no need for creating an additional weak link between RIS and modalities--- thus introducing an additional point of failure. Use of PACS Brokers is a non-standard implementation. Hence, PACS replacement is a time for NHS to review their PACS implementations so that they adopt global standards—which are key to ensuring plug & play interoperability & reducing price of NHS IT.

Exceptional circumstances where a PACS broker may be required: If there are 2 or more separate information system scheduling for the same modality—e.g. NBSS & RIS for a mammography modality, Ultrasound modality used for cardiac echoes & radiology i.e.--- scheduled by RIS for radiology & CIS for Cardiac Echoes. Use of brokers should only be on exceptional circumstances.

9. CONSISTENT IMAGE QUALITY (FROM MODALITIES to PACS)---Images once created in modalities will be sent to PACS for long term storage. Radiographers ensure that images are of good quality before transmitting to PACS. It is important that image quality is kept intact during transmission from the modality to PACS. Adherence to DICOM standards & IHE will ensure that quality of images & data are not compromised.

IHE Standards—Consistent Presentation of Images Profile of IHE

“Consistent Presentation of Images maintains the consistency of presentation for grayscale images and their presentation state information (including user an notations, shutters, flip/rotate, display area, and zoom). It also defines a standard contrast curve, the Grayscale Standard Display Function, against which different types of display and hardcopy output devices can be calibrated. Thus it supports hardcopy, softcopy and mixed environments.”

Acquisition Modalities &

PACS (as Image Manager & Image Display Actor)

must support Consistent Presentation of Images Profile of IHE

10. THREE CLICK REPORTING WORKFLOW---SINGLE SIGN-ON (SSO) , Desktop Integration (DTI) or Context Synchronization, AUTOMATIC DISPLAY RELEVANT PRIOR—

3 click reporting workflow should be possible from the RIS & PACS integration.

  1. Draw up a RIS worklist for reporting
  2. Launch a patient’s exam for reporting on RIS on left RIS monitor—automatic display of current images on PACS on middle monitor with automatic display of relevant prior on right monitor---dictate/VR a report on RIS
  3. Click on the next exam on RIS worklist—which closes the previous PACS images & launches the next patient on RIS & PACS

SSO-Process of logging in should be quick & slick. The system should support single sign-on process as used in a hospital. As a minimum, additional user name and password should not be required when using RIS & PACS. When a user logs into RIS for reporting the user credentials must be passed onto PACS with no need for additional user name and password input.

Desktop Integration (DTI) must be at exam level with Information Systems: Desktop Integration with RIS is well established with PACS.

  1. Automatic RIS to PACS Integration. In most NHS Trusts RIS is used for reporting of radiology images. For clinical reasons there should be automatic display of relevant radiology images when an exam is picked up for reporting on RIS.
  2. Manual PACS to RIS integration—when images are displayed on PACS, it should be able to display the RIS for that episode. This would be important at MDTMs, or when a request is made for a 2nd opinion etc, to allow for an addendum to be recorded on RIS.

Similarly DTI is required with other Information Systems, CIS, Ophthalmology System, Breast Screening System, Endoscopy Systems, if these images get stored on the same PACS.

Automatic Display of relevant prior Image & Report: This is hugely important for reporting Chest X-rays, oncology CTs in particular. It is well recognised that automatic prior image and report display will increase the accuracy of radiologists report & improves patient care. A good dynamic display protocol is required which automatically displays the prior similar exam on the right hand monitor of PACS (with the middle monitor displaying the current image for reporting). The associated report needs to be displayed automatically as well. Making these display automatically increases the chance of prior images & reports being reviewed & compared. This improves patient care & clinical quality.

11. BASIC RADIOLOGY IMAGE DISPLAY & MANIPULATION TOOLS: The type of display dictates the user experience of PACS:

a. user must not be overwhelmed ---“”Workflow is inversely proportional to the number of buttons on the PACS desktop”
b. number of stepsto common tasks minimised
c. consistencyof display of tools
The PACS needs to be operable by the least technically-savvy radiologist.Large number of tools to choose from on the display can be frustrating for a user. Intelligent display of commonly used image manipulation tools—windowing, measure, zoom, scroll etc should be activated with 1 mouse click/step. The tools when configured by user for a modality should be consistently displayed for each modality. (Should not require set-up every time one logs on.)

  • CR--windowing, measure, zoom etc
  • CT—scroll, windows presents, link studies, measure, zoom etc
  • MRI—synchronized scrolling with position between series in different planes etc
  • Thumbnails should be displayed for every series

Advice—Drive before you buy.

However, Basic Image Review profile of IHE will ensure that your PACS display at least has the bare minimum features required for radiology image display.

IHE Standard: Basic Image Review-

"Compliant software must provide a predictable user interface and functionality sufficient to review images for the purpose of clinical decision-making by ordering physicians: display of grayscale and color images from any modality, visual navigation of the available series of images through the use of thumbnails, side-by-side comparison of at least two sets of images (with synchronized scroll, pan and zoom for cross-sectional modalities) annotation of laterality, orientation, and spatial localization, annotation of demographics, management and basic technique information for safe identification and usage simple measurements of linear distance and angle cine capability for images that involve cardiac motion (e.g., cardiac US, XA, 500 CT or MR)"

PACS ( as Image Manager & Image Display actors) must support Basic Image Review Profile of IHE.

12. CT Image DISPLAY REQUIREMENTS: CT scanners are the main reason for data volume explosion in Radiology. Cardiology, Oncology, Colon & Trauma are the specialities where there has been CT data explosion. Storing of very thin axial slices has become the norm and will continue.
a.PACS must have an automatic & seamlessloading of MPR when thin CT slices are loaded (stand-alone modality workstations waste radiologists time & are inefficient)–automatic loading of MPR will save on unnecessary storage costs (currently many hospitals store MDCT images in 3 planes—rather than have real time MPR on CT display)
b. Allow for synchronized scrolling in 3 planes for cross sectional imaging esp MRI (CT/MRI).

c. Automatic display of relevant prior
d. Synchronized scrolling with prior scan
e. Ability to create 3D images or via a plug-in—trauma imaging, CT colonoscopy, cardiac
f. During MPR/3D viewing, super-user like radiologists should ability to save some key images(a coronal image/sag image that shows the key lesion) as a separate series for reference to the report.
g. User ability to define slab thickness and create images of different thickness real-time
h. Ability to measure distance, circumference, angle, and volume of lesions. This should be easy & intuitive.
i. Ability to measure Hounsfield density (e.g. average density of a lung nodule, with maximum & minimum density). This task should be intuitive & easy for any radiologist.
j. Scrolling speed –even with >1000 images the users should be able to scroll through images very smoothly. Cine display must be present.
k. Scrolling speed over slow networks. CT is the commonest type of imaging done on-call. Scrolling speed over slow networks is key to usage of PACS on-call. Local caching maybe a way to improve performance over slow networks.

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