1. PACS Workstations: appropriateness, performance & value for money Alan McBride * PACSnet St. Georges Hospital, London * A Department of Health, Medicines and Healthcare Products Regulatory Agency, National Evaluation Centre

2. Workstation Types Reporting (Radiology) Typically 2048 x 2560 portrait Typically 2048 x 2560 portrait Review (Wards) Typically 1280 x 1024 landscape Typically 1280 x 1024 landscape

3. CRT Display

4. Defining a Pixel by Industry Standards Pixel is viewed as a Gaussian distribution This is a convenience that ignores halation This is a convenience that ignores halation when describing the spot size in literature Pixel size is measured at the 50% point of luminance energy (FWHM) for Medical 5% point is generally not included 5% point is generally not included Measurement on a single white pixel Measurement on a single white pixel

5. Gaussian Spot Profile P45 Phosphor Microvision Scan 50% 5%

6. Spot of P104 Phosphor 5% 50%

7. Ageing CRT Ikeda M. et al (2003), Inves. Radiol, 38, pp57-63 Kuprinski E.A. & Roehrig H. (2002), Acad. Radiol., 9, pp638-645 2 - 6% drop in 2Khr (~12wks) Long Term ageing in CRT display

8. Flat Panel Display

9. Structure AMLCD Flynn et al (1999), Radiographics, 19, pp1653-1669 Blume H. et al (2002), Proceedings of SPIE, 4681, pp271-292 Transmission: Colour 6- 8% Monochrome 24%

10. Viewing Angle Dependence

11. Ageing LCD White level goes down, black level goes up. - contrast level drops. - less gray levels. Power save systems (e.g. DPMS) help a lot ! Screensavers do not help for LCD’s ! In the old days – static text displays, would ‘burn’ their image into the display phosphors Long term ageing in a LCD display 10% drop in 2Khr (~12wks) 50% drop in 30Khr (~3.5yrs)

12. Display Technology Limitations Luminance Uniformity LCD: Only P104 alike CRT: Depends on phosphor type used (P45 > P104)

13. Ambient Light Ambient light adds to the image luminance Sources are: Specular = single point source, a lamp Diffuse = scattered, unstructured light Thin LCD offers more flexibility. No direct or indirect sunlight. No direct light source. Contrast may drop drastically. LCD’s and CRT’s behave differently under changing ambient conditions. Typical illuminance in reading rooms is 300-500 Lux. DIN AAPM Ishihara S. et al (2002), Comp. Med. Imag. & Graph., 26, pp181-185

14. Differences Between CRT & AMLCD CRTAMLCD MechanismLight-emittingLight-modulating Front panelCurvedFlat Array formationScanning beamActive-matrix discrete addressing EmissionNear-LambertianNon-Lambertian Long-range interactions Veiling glareCrosstalk Pixel structureGaussian spotRectangular with sub- pixel domains NoisePhosphor noiseLC variations Cell thickness variations Spacers Structured noiseRasterNon-active pixel regions ArtifactsDeflection Landing Cell voltage variation Backlight non- uniformity TemporalFlickerFlicker and LC ghosting

15. REVIEW IMAGE DISPLAYS - Below 2 Mega Pixel & Standard PC Displays REPORTING and REVIEW IMAGE DISPLAYS – Above 2 Mega Pixel but Below 3 Mega Pixel REPORTING IMAGE DISPLAYS – Above 3 Mega Pixel CRT LCD PRICE DESIRABILITY RESOLUTION Matrix for Image Display Evaluations Landscape Portrait SCREEN SIZE 17” 21” Siemens SMM21200P Clinton DS5100P Barco MGD521-P45-75R Siemens SMM21200P Clinton DS5100P Barco MGD521-P45-75R Siemens SMM21140P Clinton DS2190P Barco MGD2621P Siemens SMM21140P Clinton DS2190P Barco MGD2621P IBM ? (9 Mega Pixel) Dome C3G-1/C3G-2 Barco Coronis 3MP1H/2H Dome C3G-1/C3G-2 Barco Coronis 3MP1H/2H Dome C5G-1/C5G-2 Siemens SMM2182L Image Systems M21LV- 65MAX Philips Fimi MGD203 Siemens SMM2182L Image Systems M21LV- 65MAX Philips Fimi MGD203 NEC LCD-2010X Barco MVD1218 Siemens SMD1898 DELL 17 SXGA Barco MVD1218 Siemens SMD1898 DELL 17 SXGA Video cards?

16. Human Computer Interface After 2 Yrs softcopy reporting 1.Regular 2 monitors for reporting 2.Presentation Software & roller ball view CT in stack mode 3.PACS Software Optimized for 2 monitors Bennet W.F. et al, (2002), J. Digit Imaging; 15 Suppl 1, pp171-174 Ohio State University Medical Centre

17. Monitor Resolution 1K vs 2K monitors Steckel R.J. et al (1995), AJR, 164, pp837-841 Steckel R.J. et al (1995), AJR, 164, pp837-841 Graf B. et al (2000), AJR, 174, pp1067–1074 Graf B. et al (2000), AJR, 174, pp1067–1074 Otto D. et al (1998), Radiology, 207, pp237-242 Otto D. et al (1998), Radiology, 207, pp237-242 Peer S. et al (2003), Eur Radiol, 13, pp413-417 Peer S. et al (2003), Eur Radiol, 13, pp413-417 CDRAD Phantom

18. Image Manipulation tools Window width/level MagnifyPan/zoomFlip/rotate Invert greyscale Local window width/level HistogramProfile Pseudo colour Image filters DSA Image merge Image crop Image stitch Toggle overlay Toggle annotations Patient anonymization

19. Window Width/Level

20. Native Image File 16 bit per pixel, 65,536 tonal steps Displayed Image 8 bit per pixel video at 1.5 to 270 cd/m 2 Selected Window Width and Level from native image mapped to CRT display. Digital World DAC CRT Display Window Level

21. 3D Study

22. Monitor Quality Control Monitor Calibration (GSDF) Weekly testing Reporting Workstations Clinical Acceptance Testing Parr L.F. et al (2001), J. Digit Imag., 14 (Suppl 1), pp22-26 Groth S. et al (2001), Radiographics, 21, pp719-732

23. Conclusion Fitness for purpose Set up a Quality Control regime (Medical Physics, Vendor, 3 rd Party...) Ensure that your display systems adhere to the GSDF at all times

24. Acknowledgements Mr. Ken Compton. (Clinton Electronics) Mr. Ivan Boeykens. (BarcoView) Mr. Dewinder Bhachu (PACSnet)

25. References Graf B. et al (2000), AJR,174, pp1067–1074 Bennet W.F. et al (2002), J. Digit Imag; 15 Suppl 1, pp171-174 Ishihara S. et al (2002), Comp. Med. Imag. & Graph., 26, pp181-185 Ikeda M. et al (2003), Inves. Radiol, 38, pp57-63 Peer S. et al (2003), Eur Radiol, 13, pp413-417 Kuprinski E.A. & Roehrig H. (2002), Acad. Radiol., 9, pp638-645 Flynn et al (1999), Radiographics, 19, pp1653-1669 Steckel R.J. et al (1995), AJR, 164, pp837-841 Parr L.F. et al (2001), J. Digit Imag., 14 (Suppl 1), pp22-26 Blume H. et al (2002), Proceedings of SPIE, 4681, pp271-292 Groth S. et al (2001), Radiographics, 21, pp719-732