PACS Workstations: appropriateness, performance & value for money

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 • Review (Wards) • 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 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 • Measurement on a single white pixel

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

6. Spot of P104 Phosphor 5% 50%

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

8. Flat Panel Display

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

10. Viewing Angle Dependence

11. Ageing LCD Long term ageing in a LCD display • 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 10% drop in 2Khr (~12wks) 50% drop in 30Khr (~3.5yrs)

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

13. AAPM DIN Ambient Light • LCD’s and CRT’s behave differently under changing ambient conditions. • Typical illuminance in reading rooms is 300-500 Lux. • 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. Ishihara S. et al (2002), Comp. Med. Imag. & Graph.,26, pp181-185

14. Differences Between CRT & AMLCD

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

16. Human Computer Interface After 2 Yrs softcopy reporting • Regular 2 monitors for reporting • Presentation Software & roller ball view CT in stack mode • 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 • Graf B. et al (2000), AJR, 174, pp1067–1074 • Otto D. et al (1998), Radiology, 207, pp237-242 • Peer S. et al (2003), Eur Radiol,13, pp413-417 CDRAD Phantom

18. Image Manipulation tools • Window width/level • Magnify • Pan/zoom • Flip/rotate • Invert greyscale • Local window width/level • Histogram • Profile • Pseudo colour • Image filters • DSA • Image merge • Image crop • Image stitch • Toggle overlay • Toggle annotations • Patient anonymization

19. Window Width/Level

20. Window Level Native Image File 16 bit per pixel, 65,536 tonal steps Displayed Image 8 bit per pixel video at 1.5 to 270 cd/m2 Selected Window Width and Level from native image mapped to CRT display. Digital World DAC CRT Display

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, 3rd 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