1. to Delivering High Quality Images in Medical Monitors

2. Your Instructor & Sencore contact Scott Reardon 1-800-SENCORE www.sencore.com

3. Calibrating Medical Monitors Founded 1951 Located in Sioux Falls, SD Leading manufacturer of innovative electronic test & measurement equipment: –Computer Monitor - high resolution computer monitor repair and calibration –Digital Video - MPEG-2/ATSC, MPEG-2/DVB, CCIR601 Serial/Parallel, QAM, and HDTV –High Definition TV - demonstration, testing and calibration applications –Professional A/V - high-end video display calibration and sound system analysis, & Home Theater –Medical - Safety Testers, Compliance Testers, and Analyzers, including SPO2 and Patient Simulators –Cable - RF distribution including CATV, MATV, satellite antenna systems & QAM applications –Broadcast - broadcast and studio settings, especially digital video and MPEG-2 applications About Sencore

4. Calibrating Medical Monitors Medical Monitors Need Calibration! Critical diagnoses depends on correct image display. Incorrect white balance causes false color imaging. Room lighting affects perceived color, brightness, and contrast. Overdriven CRTs cause picture distortion. Misadjusted User controls distort contrast and brightness ratios. Small picture flaws are magnified on high resolution displays. CRTs age - recheck calibration every 6 monthsIntroduction

5. Calibrating Medical Monitors Displays are aligned on location after installation and moving is completed Picture is optimized for room lighting conditions Reduce Doctor’s complaints about the display: That it doesn't look right. The red of the tissue doesn't look right. The display is too dark or the display is too light. The picture is blurry. Assure the doctor that the image quality is correct Produces full range of accurate colors & grayscale Telemedicine - displays need to be calibrated to match what is happening on site Why Perform Video Calibration? Introduction

6. Calibrating Medical Monitors 400-800V Neg. bias 6.3v 25KV Approx. 20-40% of HV Video Review - Producing an Image CRT gun (F1/F2, K, G1, G2) produces an electron beam Electron beam is accelerated by high voltage Phosphor screen gives off light when struck by electron beam CRT Operation

7. Calibrating Medical Monitors Video Review - Producing an Image Changing bias (G1/K voltage) changes electron beam intensity Higher bias = less beam current; less bias = more beam current Less beam current = less light output; more beam current = more light output High biasMedium biasLow bias No light output Medium light output Maximum light output How do video displays make B&W?

8. Calibrating Medical Monitors Video Review - Producing an Image White - all phosphor producing light Black - no phosphor producing light Contrast ratio - difference between black level and white level Ambient light affects contrast ratio

9. Calibrating Medical Monitors Level of video signal corresponds to CRT gun conduction & brightness Brightness (luminance) = average DC level Contrast (difference between bright/dark portions) = peak-to-peak amplitude Video signal levels specified in IRE Video Review - Producing an Image

10. Calibrating Medical Monitors Color CRTs use three electron guns Each gun is fed a separate video signal (RGB) Red + Green + Blue = white How do video displays make color? Video Review - Producing Color

11. Calibrating Medical Monitors Video Review - Producing Color Changing bias of all three guns equally produces shades of gray Neutral gray is call White Balance Good color tracking maintains “neutral” gray at all luminance levels High bias Medium bias Low bias Medium light output Maximum light output No light output

12. Calibrating Medical Monitors Video Review - Video Signals

13. Calibrating Medical Monitors Composite video contains luminance, chrominance, and sync on the same signal line. S-Video (Y/C) contains luminance and sync on one signal line, with chrominance on a second signal line. Composite Video vs.S-Video (Y/C) Video Review - Signal Types

14. Calibrating Medical Monitors Advantages of “S-video” connection over composite (RCA) connector: Separates luminance information from color information to increase B&W resolution Fewer artifacts with modern video sources like DSS and DVD Video Review - Signal Types

15. Calibrating Medical Monitors Advantage of Component vs. “S-video”: Increased color resolution Video Review - Signal Types

16. Calibrating Medical Monitors HDTV uses component rather than RGB: Requires less bandwidth More content can be stored on a DVD or broadcast. Advantage of RGB over component: RGB signals correspond directly to the CRT guns / light sources Provides best possible picture quality for analog CRT displays Video Review - Signal Types

17. Calibrating Medical Monitors Video Review - Signal Types Advantage of DVI vs. Component: DVI is digital equivalent of analog RGB DVI better for fixed pixel (non-CRT) displays connected to digital sources (DVD, digital cable set top converter, video games) Removes unnecessary analog-digital-analog conversion - enables pure digital signal to display DVI has bandwidth to address each pixel in a digital TV display individually - enabling the highest possible picture quality Component better for analog (CRT) displays - analog has theoretically better color and luminance range

18. Calibrating Medical Monitors Video Review - Formats

19. Calibrating Medical Monitors Measure of maximum number of light to dark transitions produced horizontally or vertically Horizontal resolution usually expressed in pixels Vertical resolution expressed in pixels or lines Video Review - Resolution

20. Calibrating Medical Monitors Interlace Scanning Requires 2 vertical deflection cycles to display a complete frame Vertical Jitter Achieves Higher resolution with lower bandwidth Not used in high resolution monitors 2 Fields (interlaced)1 Frame = + Video Review - Scanning

21. Calibrating Medical Monitors Progressive Scanning Scans every vertical line every frame. Helps prevents fast motion artifacts. No vertical jitter 1 Frame Video Review - Scanning

22. Calibrating Medical Monitors Light is electromagnetic energy within a narrow range of frequencies Each different wavelength of light energy (if seen alone) is perceived by the human eye/brain as a different, fully saturated, color Light & Color Theory

23. Calibrating Medical Monitors If light from the sun is equally reflected from a surface, the eye/brain sees the surface as white. If a surface absorbs all light energy and reflects none, the surface appears black. Light & Color Theory

24. Calibrating Medical Monitors If more than one wavelength is reflected, the eye/brain performs a mixing of all light energy present and perceives a single color which is a result of the mixture. Light & Color Theory

25. Calibrating Medical Monitors Eye is tri-stimulus - sees light using red, green, & blue receptors Each receptor has a different response to the light spectrum CIE Standard Observer Response Curve shows average response of each receptor across light spectrum Human Vision

26. Calibrating Medical Monitors Three characteristics define how our eye/brain sees light: Human Vision

27. Calibrating Medical Monitors Hue: Dominant wavelength, color or tint of the color. Human Vision

28. Calibrating Medical Monitors Saturation: Degree of purity from light of other wavelengths (zero saturation = white; equal energy of all wavelengths) Human Vision

29. Calibrating Medical Monitors Brightness: Perceived light energy level Human Vision

30. Calibrating Medical Monitors Light Measurement Units: Luminance (brightness): Footlambert: U.S. unit of luminance (radiated light), 1 lumen per square foot Nit (cd/m 2 ): S.I. unit of luminance (radiated light), 1 candela per square meter Light & Color Measurement Illuminance: ambient light that illuminates the display contributes to luminance that is observed from the image display reduces the contrast in the image need to block from measurement

31. Calibrating Medical Monitors Light Measurement Units: Color (hue and saturation): CIE chromaticity coordinates (x,y): From 1931 CIE Chromaticity Diagram (Kelly Chart) Light & Color Measurement What color?

32. Calibrating Medical Monitors Graphically depicts the relationship between hue and saturation. Diagram shows the pure spectral colors around the curved border The results of mixing any of these spectral colors are shown at the base and center of the diagram. CIE Chromaticity Diagram Color Measurement

33. Calibrating Medical Monitors By combining the proper mix of RGB All three guns are turned on to make white How do video displays make white? Color Measurement

34. Calibrating Medical Monitors C.I.E. coordinate x = 0.313 y = 0.329 (D) is the white color which was chosen as the standard white reference for all video display systems. (D6500) Color Measurement

35. Calibrating Medical Monitors All three guns are turned off to make black. The same point on the chart represents white and black How do video displays make black? Color Measurement

36. Calibrating Medical Monitors Using RGB light sources Any three colors not lying on a straight line with one another are color primaries. The points shown are the NTSC specified CRT phosphor color primaries for US televisions. The connecting triangle encloses the range of colors able to be produced by a CRT using these color phosphors. How do video displays make color? Color Measurement

37. Calibrating Medical Monitors Color Temperature is sometimes also used to specify different near-white colors. Color Temperature is referenced to color of carbon when heated to different temperatures (measured in °Kelvin -- °Celsius plus 273). Color Measurement Color Temperature

38. Calibrating Medical Monitors Color Measurement Different “whites”correspond to different color temperatures White sheet of paper looks different under different light CRT radiates light so color temperature not affected by lighting conditions (but brightness and contrast are)

39. Calibrating Medical Monitors Color Measurement There is an approximate correlation between color temperature and CIE chromaticity Accurate calibration is done using CIE coordinates

40. Calibrating Medical Monitors Colors which are created by heating carbon form a continuous line across the CIE Chromaticity Diagram - known as the black body curve. Only colors exactly on the curve are specified by original absolute color temperature. Color Measurement

41. Calibrating Medical Monitors Size Centering Pincushion Trapezoid Rotation Linearity 1. Calibrate Display Geometry Calibration Overview

42. Calibrating Medical Monitors Calibration Overview 2. Calibrate Display Convergence Precisely overlay red, green, and blue images at all points on display. Eliminate all color fringing effects.

43. Calibrating Medical Monitors 3. Calibrate Display White Balance Use color analyzer to measure “color” of white in center white window at high and low luminance levels Calibration Overview

44. Calibrating Medical Monitors Calibration Overview Brightness (Black Level) Contrast (White Level) Color (Saturation) Tint (Hue) Sharpness 4. Calibrate Display User Controls

45. Calibrating Medical Monitors Introducing the VP400 & 401 ‘VideoPro’ Video Generator The VP400 & 401 ‘VideoPro’ Multimedia video generators deliver the HDTV, NTSC, RGB, DVI & RF Video Signals You Need for Accurate Service & Alignments of Monitors & Direct View Displays.

46. Calibrating Medical Monitors Composite S-Video Component/RGB VESA/HDTV Battery operated (8 hours) Video Generator NTSC RF (VP401) DVI (VP401)

47. Calibrating Medical Monitors SMPTE Bar Check and adjust color level and hue controls. Check color demodulator accuracy. Video Generator

48. Calibrating Medical Monitors Color Bar Check for primary (red, green, blue) and secondary (cyan, magenta, yellow) colors to confirm proper chroma processing. Video Generator

49. Calibrating Medical Monitors Decoder Check Video Generator Check color decoder/matrix circuit to determine if any red or green color emphasis (“push”) or de-emphasis. The 0 center bar of each color as viewed through its respective color filter should be the same intensity as the 75% reference white. 0+5+10+20+15+25-25+20-10-15-5 75% white reference 75% saturated color level

50. Calibrating Medical Monitors Decoder Adjust Video Generator Set color decoder/matrix circuits for accurate color. View color primary through color filter & adjust chroma gain to match intensity of white bar and surrounding color. Adjust chroma hue to match intensity of secondary color bars.Blue section: set “User Menu” Color & Hue controls. Red & green sections: set “Service controls” 75% white reference Primary color sections Secondary color bars

51. Calibrating Medical Monitors Focus Check for proper static & dynamic focus operation at screen center & edges. Video Generator

52. Calibrating Medical Monitors Converge Converge display over entire picture area. The red, green and blue segments should form straight lines of equal thickness. The line intersections show steps from the straight ideal converged lines. Video Generator

53. Calibrating Medical Monitors Crosshatch (4:3) Check and adjust convergence and linearity. Video Generator

54. Calibrating Medical Monitors Linearity Video Generator Check and adjust deflection linearity, set geometry controls, color convergence adjustments.

55. Calibrating Medical Monitors Anamorphic Check accuracy of widescreen stretch feature (from 4:3 to 16:9). Video Generator

56. Calibrating Medical Monitors Overscan Check and adjust display geometry, including picture centering, size, trapezoid (keystone) correction, pincushion (bow) correction, and linearity. Video Generator electrical center 5% overscan (green line) 10% overscan (red line)

57. Calibrating Medical Monitors Staircase Check video amplifier linearity and gray scale tracking. Adjust G2 (screen) control to proper setting. Video Generator

58. Calibrating Medical Monitors Horizontal Staircase Check gray scale tracking of CRT projectors with red and blue overdrive on sides of screen. Video Generator

59. Calibrating Medical Monitors Pluge (Picture Line-Up Generator Equipment) Check for proper black level (brightness) and white level (contrast) setup. Includes alternating black/blacker-than-black section. Alternating Black 10 IRE Video Generator

60. Calibrating Medical Monitors Needle Check for Sweep Velocity Modulation (SVM) operation, high voltage regulation, and setting Contrast & Brightness on CRT displays. Video Generator

61. Calibrating Medical Monitors Ramp Visual check of grayscale tracking. Poor performance causes visual color tint at one or more light levels. Checks digitizing linearity of video signal processors. Poor performance causes vertical bands. Video Generator

62. Calibrating Medical Monitors Window Check chromaticity with color analyzer. Adjustable IRE level window with pluge bars to monitor black level. Video Generator

63. Calibrating Medical Monitors Regulate Check high voltage and scan current regulation. Video Generator Black / White alternating 1 pixel wide

64. Calibrating Medical Monitors Raster Check purity & white balance. Includes adjustable 0-100 IRE levels. Color can be gated on/off to produce red, green, blue, cyan, magenta & yellow raster. Video Generator

65. Calibrating Medical Monitors Checker Check for regulation of low voltage supply to video amps and video ringing. Should see sharp vertical lines with no video ringing. Video Generator

66. Calibrating Medical Monitors Lo-Hi Tracking Video Generator Set Contrast & Brightness on fixed-pixel (non-CRT) displays. Increase brightness to see black (-4 IRE) vertical bar, then decrease until bar just disappears. Increase brightness control if needed to make 2.5% and 5% boxes both visible. Set contrast so 95% and 97.5% boxes are visible. 0 % (black) 5 % 2.5 % - 4IRE (blacker than black) 97.5 % 100 % (white) 95 %

67. Calibrating Medical Monitors Multiburst Check for ringing, smearing, and sharp resolution. Increase Sharpness control until all bursts are equal brightness without ghosting. Video Generator

68. Calibrating Medical Monitors Sharpness Video Generator Align controls that artificially enhance picture transitions (contrast, picture, aperture, scan-velocity modulation). SVM - bottom center vertical lines straight & same width, set for least impact on width of black lines compared to white lines. Contrast/Picture/Aperture - sharp B/W transitions, white edges not blurred or blooming, no ghosting, clear, bright multiburst. Straight, same width Clear, same brightness No blooming

69. Calibrating Medical Monitors Different display types produce different light spectrums Our eyes still see the same result To provide accurate measurements Colorimeter must use CIE standard observer filters that replicate eye response What worked for CRTs doesn’t work for other display types 3 chip DLP Projector CRT Projector Direct View CRT LCD Projector Color Calibration

70. Calibrating Medical Monitors Colorimeter is a tri-stimulus measurement device Filters and light sensors to separate light into R,G & B Output voltages proportional to applied light Color Calibration

71. Calibrating Medical Monitors CP5000 Color Analyzer Accurate method to set white balance (set to industry specs for best video display performance) Objective test (measure light produced by display) Easy to use and interpret (x-y and RGB bar graphs) CP500x accurate for all display types NIST traceable CP5001 ‘ColorPro’ Color Analyzer CP5000 ‘ColorPro’ Color Analyzer Color Calibration

72. Calibrating Medical Monitors Probe connects to PC’s serial or USB port or Pocket PC Select standard preset white references, or input custom setting Flexible refresh rate synchronization for testing at a fixed display format or to follow changing formats. Luminance measured in units of nits or footlamberts. Color Calibration ColorPro Analyzer overview

73. Calibrating Medical Monitors Color Calibration Delta RGB analog bar graph - quick adjustment of cutoff and drive controls Change resolution for fine touchup adjustments Selectable color reference ColorPro Analyzer overview

74. Calibrating Medical Monitors Color Calibration ColorPro Analyzer overview Chromaticity diagram display provides quick visualization of control interaction Center target defines selected white reference color coordinates Measurement cursor & color “steering lines” track control adjustments

75. Calibrating Medical Monitors Color Calibration ColorPro Analyzer overview Calibration Report printout provides documentation & re- calibration reference Pre-and post-calibration performance easily documented Standard or extended form tracks display at high & low luminance, or at multiple luminance points (ISF)

76. Calibrating Medical Monitors ColorPro Analyzer overview Identifies when next calibration is due Shows before and after color temperatures Documentation that display is optimized Color Calibration

77. Calibrating Medical Monitors Calibration Library- On-line library of digital service menu adjustment codes available to ColorPro owners to simplify white balance calibration without service literature. Color Calibration

78. Calibrating Medical Monitors White Balance Calibration Accurate image colors are only possible when white balance is correct & tracks accurately from black to white. White balance is produced at all luminance levels when: 1) RGB sources/CRT guns balanced/biased to produce desired white reference at darkest gray 2) RGB video amplifiers have correct gain & linearity to produce desired white reference at all luminance levels from black to gray to white Brightness control adjusts light level of the darkest parts of picture (should be called black level control) Contrast control adjusts light level of the brightest picture parts (should be called brightness control). White Balance/Gray-Scale Tracking Overview

79. Calibrating Medical Monitors White Balance Calibration Brightness & Contrast controls affect RGB output equally and do not affect the white balance of dark or bright picture portions If the display’s gray scale doesn’t track accurately adjusting brightness or contrast controls produces a noticeable color shift due to the luminance level change Normal Lower Luminance Poor tracking Lower Luminance Good tracking White Balance/Gray-Scale Tracking Overview - continued

80. Calibrating Medical Monitors White Balance - preliminary setup 1. Display the Pluge, Window, or Staircase pattern. White Balance Calibration

81. Calibrating Medical Monitors Pluge Pattern alternating 0/7.5 IRE Black 10 IRE

82. Calibrating Medical Monitors 2. With the contrast control set to approximately 3/4 of full scale, adjust the brightness control for proper display of black in the Pluge or Window pattern (for the Staircase pattern, make the first bar black and the second bar just barely visible). White Balance Calibration White Balance - preliminary setup

83. Calibrating Medical Monitors White Balance Calibration 3. Display the Needle pattern. 4. Adjust the contrast control for maximum brightness with no signs of blooming in the maximum white bar of the gray scale or raster distortion of the needle pulses. White Balance - preliminary setup - CRT displays

84. Calibrating Medical Monitors White Balance Calibration White Balance - preliminary setup - Fixed pixel displays 3. Display the Lo-Hi Tracking pattern. 4. Adjust Contrast control as high as possible without white clipping or compression. 97.5 % 100 % (white) 95 %

85. Calibrating Medical Monitors Color Tracking Adjustment Controls Cutoff/Bias controls adjust color balance at low luminance levels. Gain/Drive controls adjust color balance at high luminance levels. Gain/Drive Controls Cutoff/Bias Controls White Balance Calibration White Balance

86. Calibrating Medical Monitors

87. 1. Determine the white reference/CIE chromaticity coordinates to which the display is to be adjusted. Note: Most displays should be adjusted to the CIE D65 daylight standard (x = 0.313, y = 0.329). This is the NTSC and ATSC white reference standard. White Balance Calibration

88. Calibrating Medical Monitors 2.Display a 20 or 30 IRE white window pattern on the monitor (1 lumen - just enough light to get a reading). Note: If starting from scratch after a CRT or other video component replacement, preset the display’s drive (gain) controls for maximum brightness and the cutoff (bias) controls for minimum brightness. White Balance Calibration

89. Calibrating Medical Monitors 3. Leaving the cutoff control for the initially strongest color (as viewed on the dim CRT) at its original or preset level, adjust the other two cutoff controls to obtain color balance at the desired white reference. White Balance Calibration

90. Calibrating Medical Monitors 4. Select a 80-100 IRE level window pattern. 5. Leave the drive control for the initially weakest color (as viewed on the bright CRT) at its original or preset level, and adjust the other two drive controls to again obtain color balance at the desired white reference. White Balance Calibration

91. Calibrating Medical Monitors 6. Repeat steps 2-5 until the display’s color temperature remains relatively constant (tracks) over the full range of IRE levels or contrast control adjustment. White Balance Calibration

92. Calibrating Medical Monitors Calibrating User Controls When the color temperature is calibrated perform final adjustment of the User controls at typical ambient lighting. CRT Displays 1. Brightness (black Level) 2. Sharpness/Enhancement 3. Contrast (white Level ) 4. Color 5. Hue/Tint Fixed Pixel Displays 1. Brightness & Contrast 2. Sharpness/Enhancement 3. Color 4. Hue/Tint

93. Calibrating Medical Monitors Brightness control adjusts light level of the back or darkest luminance portions of the picture. If set too dark: –subtle dark gray details of the scene are lost to black If set too bright: –darkest grays and deep blacks are all a lighter gray, which effectively lowers the contrast ratio of the display and reduces picture quality Brightness Control

94. Calibrating Medical Monitors Contrast control adjusts light level of the white or high luminance portions of a scene. Sometimes labeled picture control - should be labeled white level control If set too low: –picture image is dim, whites become dull & image loses its luster because the contrast ratio is too low. If set too high (this is often the factory setting): –power supply may be overdriven causing raster distortion –may cause pixel blooming (occurs when the screen pixels are struck so hard that light spreads to the adjacent pixels, defocusing the white image) Contrast Control

95. Calibrating Medical Monitors Artificially enhance picture transitions between black & white Recommend turning SVM off Enhancement Controls - (Sharpness, Picture, Aperture, Scan Velocity Modulation)

96. Calibrating Medical Monitors Brightness Control - Brightness Control - CRT displays 1. Select VP300 Pluge pattern. 2. Watch second box from the inside (alternating between 7.5 IRE/black & 0 IRE/blacker-than-black). 3. Adjust the control until the 7.5 IRE & 0 IRE levels appear the same and no flashing can be seen. The outer 10 IRE box should still be slightly visible. NTSC 0 /7.5 IRE 7.5 IRE 10 IRE 7.5 IRE HDTV 0 /- 4 IRE 0 IRE 10 IRE 0 IRE Calibrating User Controls

97. Calibrating Medical Monitors Calibrating User Controls Brightness Control - Brightness Control - Fixed Pixel displays 1. Select VideoPro’s Lo-Hi Tracking pattern. 2. Increase brightness to see black (-4 IRE) vertical bar, then decrease until bar just disappears. 0 % (black) - 4IRE (blacker than black) 97.5 % 100 % (white) 95 %

98. Calibrating Medical Monitors Calibrating User Controls Brightness Control - Brightness Control - Fixed Pixel displays 3. Increase the Brightness control if needed to make 2.5% and 5% boxes both visible. 4. Set contrast so 95% and 97.5% boxes are visible. 0 % (black) - 4IRE (blacker than black) 97.5 % 100 % (white) 95 % 5 % 2.5 %

99. Calibrating Medical Monitors Calibrating User Controls Sharpness/Enhancement Controls - Sharpness/Enhancement Controls - Fixed Pixel & CRT displays Straight, same width, no ghosting 1. Select the VideoPro’s Sharpness pattern. 2. Adjust sharpness control while watching the bottom vertical lines. Set for best balance between ghosting and poor focus. too high - faint ghosting beside line too low - appears out of focus and lost resolution

100. Calibrating Medical Monitors Calibrating User Controls Sharpness/Enhancement Controls - Sharpness/Enhancement Controls - Fixed Pixel & CRT displays 3. If the top multiburst section becomes too dull or unclear increase the Sharpness control for the best compromise Clear, same brightness

101. Calibrating Medical Monitors Calibrating User Controls 1. Select VideoPro’s Needle Pulse pattern. 2. Watch the vertical lines as you adjust the contrast: top white bar is same width as 4 gray bars below vertical lines are straight. If contrast is too high, needle pulses will bend & boxes bloom 3. Recheck Brightness control setting and readjust if needed. Contrast Control Contrast Control - CRT Displays same width (no blooming) Straight (no raster distortion)

102. Calibrating Medical Monitors Color Level Control 1. Select SMPTE Color Bars pattern. 2. View pattern with blue filter, paying attention to large top outside blue & white bars, and small bars below them. 3. Adjust Color control to make these bars appear to have the same intensity (brightness) level. 4. Remove blue filter and view yellow & red bars. They should be very colorful without blooming into adjacent bars. Top Outside Bar Small Center Bar Large Outside Bar Calibrating User Controls

103. Calibrating Medical Monitors Tint Control 1. Select SMPTE Color Bars pattern. 2. View pattern with blue filter, paying attention to the Cyan/Magenta bars that are located above and below one another. 3. Adjust Tint/Hue control to make these bars appear to have the same intensity (brightness) level. Magenta Cyan Calibrating User Controls

104. Calibrating Medical Monitors Decoder Adjust Color, Hue and Decoder/matrix Use if display has 2 User Controls and color Service Adjustments (RYR/red gain, RYB/red hue, GYR/green gain, GYB/green hue) Set color decoder/matrix circuits for accurate color.

105. Calibrating Medical Monitors 1. View color primary through color filter & adjust chroma gain to match intensity of white bar and surrounding color. Blue section: set “User Menu” Color & Hue controls. Red & green sections: set “Service controls” (RYR/red gain, RYB/red hue, GYR/green gain, GYB/green hue) 2. Adjust chroma hue to match intensity of secondary color bars in each color block. 75% white reference Primary color sections Secondary color bars

106. Calibrating Medical Monitors Benefits of a Properly Calibrated Video Display: Displays a sharper-focused, full resolution image. Shows full detail in both the darkest & brightest parts of all scenes. Is properly matched to the viewing environment. Produces a full range of accurate colors, including flesh tones. Minimizes picture artifacts (distortions) Satisfied user

107. Calibrating Medical Monitors DICOM Overview A trauma patient is admitted at an outpatient clinic or rural clinic at a remote location. Several X-rays are taken and sent to a hospital for consultation. Imagine the following:

108. Calibrating Medical Monitors DICOM Overview How can we make sure that what the physician sees at the clinic matches what is being displayed on the radiologist softcopy workstation at the hospital? ? ? ? ?

109. Calibrating Medical Monitors DICOM - Overview The image is also sent to another radiologist for a second opinion. This radiologist has a diagnostic viewing station from another vendor - a different monitor and video display card. As a matter of fact, he has a new flat panel display instead of a conventional CRT. How do we make sure that the image again looks identical? ? ? ? ? ?

110. Calibrating Medical Monitors DICOM - Overview Everyone misses something among the myriads of pixels that are tape archived for colleagues and lawyers to examine with 20/20 hindsight vision. Perhaps the missed findings were apparent in the image data, but a once- new PACS monitor had lost its ability to display those subtle differences. How can you know? What will you say when they ask what steps you took to assure that the display equipment you used was up to par?

111. Calibrating Medical Monitors DICOM - Overview A digital signal from an image can be measured, characterized, transmitted, and reproduced objectively and accurately. However, the visual interpretation of that signal is dependent on the varied characteristics of the systems displaying that image. [Without a standard] images produced by the same signal may have completely different visual appearance, information, and characteristics on different display devices. In medical imaging it is important that there be a visual consistency in how a given digital image appears, whether viewed, for example, on the display monitor of a workstation or as a film on a light-box. excerpts taken from the Forward to Digital Imaging and Communications in Medicine (DICOM) Part 14: Grayscale Standard Display Function

112. Calibrating Medical Monitors DICOM - Overview These issues are addressed the D igital I maging and Co mmunications in M edicine (DICOM) standard (PS 3.14-2003) Part 14 of this standard deals with grayscale consistency. Jointly developed by American College of Radiology (ACR) & National Electrical Manufacturers Association (NEMA) Standard method for transferring images and associated information Allows images to be displayed consistently on different softcopy and hardcopy devices –devices manufactured by various vendors –devices having different technologies (CRT, LCD) –devices with different characteristics (max. Brightness and/or Density) –different ambient light environments.

113. Calibrating Medical Monitors DICOM - Display Gamma CRT and LCD monitors have a fixed power-law relationship between output luminance and input drive signal (gamma) of about 2.5: output luminance = input drive 2.5 Signals applied to CRTs &LCD require an inverse gamma offset to counteract the display’s gamma This correction produces a linear relationship between the driving signal and resulting light output

114. Calibrating Medical Monitors Our eye-brain detection system is not linear –much less sensitive in the blacks than in the whites –why map all black values into luminance changes to display on the monitor when we can’t notice the differences between small black value changes? DDL* values of darker areas mapped into large luminance increments DDL* values of whiter areas mapped to smaller luminance increments Resulting curve is standardized as the DICOM Grayscale Standard Display Function (GSDF) DICOM - Display Gamma *Digital Driving Level (DDL): digital value applied to a Display System to produce a luminance output

115. Calibrating Medical Monitors DICOM - Perceptual Linearization GSDF produces a display function that matches the perceptual characteristics of our eyes Just-Noticeable Difference (JND) - smallest luminance change that an average person can just perceive (approximately 256 shades of gray) “Perceptually linearized” display - equal changes in driving levels produce perceptually equivalent changes in luminance across the entire luminance range. Most digital radiologic images display 256 shades of gray - the approximate maximum number of Just Noticeable Differences that we can perceive

116. Calibrating Medical Monitors.01.1 1 10 100 1000 2004006008001000 Grayscale Standard Display Function JND Index Same number of Just Noticeable Difference == same perceived contrast Different change in absolute luminance Equal steps in perceived brightness represent equal steps in the acquired image data DICOM - Perceptual Linearization

117. Calibrating Medical Monitors DICOM - Perceptual Linearization

118. Calibrating Medical Monitors GSDF provides a way to standardize image displayed on monitors having different inherent brightness and response curves Used to recalibrate monitors whose luminance and response curves have changed over time Simply calibrate the monitor & printers according to this curve Calibration requires luminance meter that can be placed on the monitor sothe light output (luminance) can be measured at multiple digital driving levels (DDLs) / luminance levels Luminance meter output is compared with the actual Grayscale Standard Display Function (GSDF) and differences can be calculated and saved A corrective transfer function is then loaded directly to the video display controller DICOM - Perceptual Linearization

119. Calibrating Medical Monitors DICOM - Color Lookup Table Video Card Look Up Table Digitized images are made up of a matrix of pixels, each possessing at least three dimensions: two (or more) spatial and one intensity value. The quantized dimensions are stored on the computer as a file of binary numbers. In order to see the image on the computer monitor, the image pixel values must be mapped, one-to-one, to screen pixel values, via a Look Up Table (LUT). The LUT transfer function determines what screen values correspond to image pixel intensity values at all coordinates in the image.

120. Calibrating Medical Monitors If each image intensity value is mapped to its corresponding screen value the LUT is a linear function and can be graphed as a 45° straight line. By modifying the slope of the transfer function and screen mapping, LUT image intensity values may be selectively increased or decreased to perceptually equalize luminance steps in the image DICOM - Color Lookup Table

121. Calibrating Medical Monitors DICOM - Calibrating Displays Procedure for Calibrating Gray scale (B&W) Monitors Calibrate each monitor regularly Calibrate under normal viewing & lighting conditions Adjust monitor contrast and brightness before/during calibration and never again Calibrate with always the same background intensity (about 20%, or a value comparable to the average intensity emitted from the monitor) Calibrate to match the standard display function (DICOM)

122. Calibrating Medical Monitors Your Sencore contact: Scott Reardon 1-800-SENCORE www.sencore.com Questions? Remember: