National Guidance on Standards for PACS Image Display
National Guidance on Standards for PACS Image Display Devices Dr Rhidian Bramley PACS & Teleradiology SIG Hillingdon, London 22 Nov 2006 FAQ Is the LSP PACS web client suitable for diagnostic use? Are there different recommendations for diagnostic and review workstations? Are there different recommendations for different modality workstations? How do you decide what specification is appropriate for A&E, clinics, wards, theatres etc. Should we deploy 2, 3 or 5 MP display devices on reporting workstations?
Display Device QA Guidance National AAPM TG18 (USA) DIN V 6868-57 (Germany) IPEM 91 (UK) RCR (UK) Connecting for Health (England) International
SMPTE VESA FPDM ISO 9241 and 13406 DICOM GSDF and GSPS IEC 61223-3-6 UK Guidance Drivers & Objectives Assist UK PACS deployments Guidance on purchase and QA of display devices for PACS projects & business cases Promote clinical safety
Set minimum standards Achieve benefits of PACS Support clinical workflow Provide realistic achievable targets UK Guidance Scope All PACS display devices used for clinical image interpretation because by definition there is an associated clinical risk Specify QA tests and minimum standards for a display device to reproduce a DICOM test image Assess whole imaging chain from PACS server to workstation display (including effect of room lighting)
Provide guidance on how to view images To optimise spatial and contrast resolution Classification of Display Devices Are there different recommendations for diagnostic and review workstations? If so, what constitutes a review workstation? AAPM TG18 Classification Primary display systems those used for the interpretation of medical images. They are typically used in radiology and in certain medical specialties such as orthopedics.
Secondary display systems those used for viewing medical images by medical staff or specialists other than radiologists after an interpretive report is rendered. IEC Classification Primary Usage use of an image display system or its components for the interpretation of medical images toward rendering clinical diagnosis Secondary Usage use of an image display system or its components for viewing medical images for medical purposes other than primary usage
RCR/CfH Guidance This guidance deals with the QA of primary diagnostic display devices used for clinical image interpretation. Where images are reviewed without a requirement for clinical interpretation, the image quality is considered to be of secondary importance. The quality of display in these circumstances should be considered locally, depending on the purpose of the review. Classification of Display Devices Are there different recommendations for different modality workstations? Mammography
Plain Radiography CT, MR Classification by Image Modality DIN V 6868-57 Class 1 (projection radiography) Class 2 (cross sectional imaging) IEC 61223-3-6 Mammography Radiography, Fluoroscopy CT, MRI US, NM Classification by Area? How do you decide what specification is appropriate for Radiology, A&E, clinics,
wards, theatres etc? Should everyone have the same display devices? How do you justify one clinical area having a better workstation that another? Clinical Risk Assessment What can go wrong Patient may be harmed as a result of inadequate quality of the PACS display device How often How bad Need for action? Clinical Risk Assessment How often
Radiology Fracture clinic A&E ITU Chest clinic Theatres Wards How bad Total Clinical Risk Assessment Radiology Fracture clinic A&E ITU
Chest clinic Theatres Wards How often 5 3 4 2 2 1 2 How bad Total
Clinical Risk Assessment Radiology Fracture clinic A&E ITU Chest clinic Theatres Wards How often 5 3 4 2 2 1 2
How bad 5 5 3 4 3 3 1 Total Clinical Risk Assessment Radiology Fracture clinic A&E ITU
Chest clinic Theatres Wards How often 5 3 4 2 2 1 2 How bad 5 5 3
4 3 3 1 Total 25 15 12 8 6 6 6 Clinical Risk Assessment What can go wrong Patient may be harmed as a result of
inadequate specification and QA of the PACS workstation How often How bad Need for action? Evidence base examples 1 Effect of Monitor Luminance and Ambient Light on Observer Performance in Soft-Copy Reading of Digital Chest Radiographs Radiology 2004;232:762-766 When adequate window width and level are applied to soft-copy images, the primary diagnosis with chest radiographs on the monitor is unlikely to be affected under low ambient light and a monitor luminance of 25 foot-lamberts or
more. Evidence base examples 2 Personal Computer versus Workstation Display: Observer Performance in Detection of Wrist Fractures on Digital Radiographs Radiology 2005;237:872-877 The results of this study showed that there was no difference in accuracy of observer performance for detection of wrist fractures with a PC compared with that with a PACS workstation. Evidence base examples 3 ROC Analysis for Diagnostic Accuracy of Fracture by Using Different Monitors Journal of Digital Imaging 2006;19: 276
A significant difference was observed in the results obtained by using two kinds of monitors. Color monitors cannot serve as substitutes for monochromatic monitors in the process of interpreting computed radiography (CR) images with fractures. Options to Mitigate Risk Install higher spec display device Optimise QA - ensure workstation is configured correctly (+ ambient lighting) Training - ensure workstation is used correctly Implement hot reporting service Disallow clinical image interpretation on the workstation
Importance of Clinical Workflow Workflow should dictate where diagnostic quality display devices are positioned Providing it does not render then non-diagnostic! May use workflow to justify a higher spec display device in some areas Where viewing conditions can not be optimised fully e.g. operating theatres, angiography rooms Where large numbers of plain radiographs reported to reduce requirements for systematic magnification (spatial resolution) and windowing (contrast resolution). RCR guidance on how to view images To optimise spatial resolution View image fully in maximum available screen area to optimise
pattern recognition of non-spatially limited abnormalities Systematically magnify image to acquisition resolution or greater (100%, 200% etc) to reveal spatial detail zoom and pan image around screen use magnifying glass tool Studies suggest that there is little reduction in the diagnostic power of using these techniques when compared to displaying the whole image at 1:1 on higher resolution screens, but there is an increase in the time taken to make a report. High fidelity dual screen displays (>= 3 MP) are recommended in radiology and other areas where large numbers of radiographic images are reported, to reduce reporting times and thereby optimise department workflow. RCR guidance on how to view images To optimise contrast resolution
View image at different window level and window width presets to optimise demonstration of different structures e.g. soft tissue, lung, bone windows .By changing the centre (level) and range (width) of the greyscale values presented, it should be possible to demonstrate all the grey-scale data represented in the image. The minimum specification of a display device in terms of contrast resolution parameters is therefore somewhat arbitrary, and depends on how the windowing tools are used during normal workflow. High fidelity display devices are recommended in radiology and other areas where large numbers of images are reported to reduce requirements for windowing images, and thus assist in reporting workflow. RCR Guidance Minimum 
Recommended  Screen Resolution  (Native Pixel Array) Screen Size (Viewable Diagonal) Maximum Luminance >= 1280 x 1024  (~ 1.3 megapixels) >= 42 cm (~17) >= 1500 x 2000  (~ 3 megapixels) >= 50 cm (~ 20) > 170 cd/m2 
>= 500 cd/m2  Luminance Contrast Ratio (Max/Min) Grey-scale Calibration >= 250:1   >= 500:1 Within 10% GSDF  Calibrated to GSDF  Grey-scale bit depth
8 bit grey-scale (24 bit colour)  Video Display Interface Digital-analogue >= 10 bit grey-scale Pixel Defects  ISO 13406-2 class Digital video interface (DVI) Class 1 (0 defects) Class 2 (2 per million)
IPEM 91 GUIDANCE Physical parameter Frequency Remedial level Image display monitor condition Daily to weekly Image display monitors should be clean, and the perceived contrast of the test pattern should be consistent between monitors connected to the same workstation. Verify that the 5% and 95% patches are visible.
Greyscale contrast luminance ratio 3 monthly Ratio white to black < 250 Distance and Angle Calibration 3 monthly 5 mm 3 Resolution
3 monthly Grade AAPM TG18-QC resolution patterns according to the reference score (CX > 4) Greyscale drift 6 to 12 monthly Black baseline 25% White baseline 20% DICOM greyscale calibration 6 to 12 monthly
GSDF 10% Uniformity 6 to 12 monthly U% > 30% Variation between monitors 6 to 12 monthly Black baseline > 30% White baseline > 30%
Room illumination 6 to 12 monthly > 15 lux FAQ Is the LSP PACS web client suitable for diagnostic use? Are there different recommendations for diagnostic and review workstations? Are there different recommendations for different modality workstations? How do you decide what specification is appropriate for A&E, clinics, wards, theatres etc. Should we deploy 2, 3 or 5 MP display devices on reporting workstations?
Summary RCR Guidance Set achievable minimum standard for all workstations used for clinical image interpretation Number and locations of clinical diagnostic workstations determined by and workflow analysis and QA programme Recommended higher standard for some workstations to optimise clinical safety and workflow Where large numbers of plain radiography images reported Where viewing conditions can not be optimised fully Which is the PACS workstation?
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