The use of color LCDs in medical imaging is growing as more clinical specialties use digital images as a resource in diagnosis and treatment decisions. Telemedicine applications such as telepathology, teledermatology, and teleophthalmology rely heavily on color images. However, standard methods for calibrating, characterizing, and profiling color displays do not exist, resulting in inconsistent presentation. To address this, we developed a calibration, characterization, and profiling protocol for color-critical medical imaging applications. Physical characterization of displays calibrated with and without the protocol revealed high color reproduction accuracy with the protocol. The present study assessed the impact of this protocol on observer performance. A set of 250 breast biopsy virtual slide regions of interest (half malignant, half benign) were shown to six pathologists, once using the calibration protocol and once using the same display in its "native" off-the-shelf uncalibrated state. Diagnostic accuracy and time to render a decision were measured. In terms of ROC performance, Az (area under the curve) calibrated = 0.8570 and Az uncalibrated = 0.8488. No statistically significant difference (p = 0.4112) was observed. In terms of interpretation speed, mean calibrated = 4.895 s; mean uncalibrated = 6.304 s which is statistically significant (p = 0.0460). Early results suggest a slight advantage diagnostically for a properly calibrated and color-managed display and a significant potential advantage in terms of improved workflow. Future work should be conducted using different types of color images that may be more dependent on accurate color rendering and a wider range of LCDs with varying characteristics.

Abstract— A methodology and associated software modules for calibration, characterization, and profiling of color LCDs for color‐critical applications in medical imaging is described. Supporting analyses reveal very high color‐reproduction accuracy as determined by CIE DE2000 color differences for 21 0 test colors uniformly distributed in CIE Lab color space. The impact of the LCD tone‐reproduction curve on color‐reproduction accuracy is compared for two tone‐reproduction curves of special interest in medical imaging: the DICOM gray‐scale standard display function and the CIE L* standard lightness function. The initial results from a psychophysical investigation of the diagnostic performance of trained pathologists viewing “virtual” breast biopsy slides are reported and the diagnostic performance achieved with calibrated, color‐managed LCDs with uncalibrated LCDs without the benefits of color management is compared.

A methodology and associated software modules for calibration, characterization and profiling of color LCDs for color-critical applications such as medical imaging is described. Supporting analyses reveal very high color reproduction accuracy as determined by CIE DE2000 color differences for 210 test colors uniformly distributed in CIE Lab color space.

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Our laboratory has investigated the efficacy of a suite of color calibration and monitor profiling packages which employ a variety of color measurement sensors. Each of the methods computes gamma correction tables for the red, green and blue color channels of a monitor that attempt to: a) match a desired luminance range and tone reproduction curve; and b) maintain a target neutral point across the range of grey values.All of the methods examined here produce International Color Consortium (ICC) profiles that describe the color rendering capabilities of the monitor after calibration. Color profiles incorporate a transfer matrix that establishes the relationship between RGB driving levels and the International Commission on Illumination (CIE) XYZ (tristimulus) values of the resulting on-screen color; the matrix is developed by displaying color patches of known RGB values on the monitor and measuring the tristimulus values with a sensor. The number and chromatic distribution of color patches varies across methods and is usually not under user control.In this work we examine the effect of employing differing calibration and profiling methods on rendition of color images. A series of color patches encoded in sRGB color space were presented on the monitor using color-management software that utilized the ICC profile produced by each method. The patches were displayed on the calibrated monitor and measured with a Minolta CS200 colorimeter. Differences in intended and achieved luminance and chromaticity were computed using the CIE DE2000 color-difference metric, in which a value of ΔE = 1 is generally considered to be approximately one just noticeable difference (JND) in color. We observed between one and 17 JND's for individual colors, depending on calibration method and target.As an extension of this fundamental work 1 , we further improved our calibration method by defining concrete calibration parameters for the display, using the NEC wide gamut puck, and making sure that those calibration parameters did conform, with the help of a state of the art Spectroradiometer, PR670. As a result of this addition of the PR670, and also an in-house developed method of profiling and characterization, it appears that there was much improvement in ∆E, the color difference.

At the University of Arizona a research project is underway which addresses consistent color and consistent gray-scale reproduction for digital color displays used in medical image interpretation, specifically for Pathology. Now the University of Arizona can enter the field of ICC Profiling and Color Management.Of particular interest are Verification of PerfectLum Software, conformance and deviation and the maximum GSDF Error. Verification of PerfectLum Software seemed to be successful. FIT and LUM tests were performed to verify the conformance and the deviation was quantified. The maximum GSDF Error turned out to depend slightly on the bandwidth of the PR-670 Spectrophotometer. Measurements were made at two settings each of Normal and Fast. At the setting "Normal" the maximum GSDF Errors were 8.6% and 6.1 %. At the setting "Fast" the maximum GSDF Errors were 7.44 % and 5.76%.With respect to the results, all three objectives were met and the PerfectLum calibrated display was confirmed to the AAPM TG18 standards.

Purpose: To quantify the impact of modifications to an IMRT planning system using the TG1 19 assessment score as an indicator of improvement. Method and Materials: Evaluation of an IMRT system following the TG1 19 protocol was initially performed to establish baseline results. The TG1 19 evaluation set consisted of five IMRT test cases planned and delivered to a 30 cm × 30 cm × 15 cm solid water phantom. Per‐field measurements were collected using a diode array, and composite measurements were collected using film and an ionization chamber. Measurements were compared to calculation to determine TG1 19 confidence limits. The original plans were then modified to include table attenuation, previously omitted by the planning system. Without modifying the incident radiation fields, the plans were recalculated on the modified phantom, which includes a table model. The resultant calculations were compared to the original measurements, and new TG1 19 confidence limits were determined. Results: The baseline TG1 19 assessment resulted in confidence limits of 4.36%, 23.8% and 9.16% for diode array, composite film, and composite ion chamber measurements, respectively. The TG1 19 assessment after plan modification resulted in confidence limits of 4.36%, 19.5%, and 8.54%. The TG1 19 confidence limits were reduced by 4.30% and 0.62% in film and ion chamber, respectively, which is a relative improvement of 18.1% and 6.8%. Conclusions: Using a single set of measurements, modifications to the planning system via the addition of a table model resulted in quantifiable improvement in TG1 19 assessment results. In this system, the addition of a table model improved the agreement between calculation and measurement, as indicated by the TG1 19 confidence limit results. The improvement was only observed in confidence limits from composite comparisons using film and ion chamber, but not observed for per‐field comparisons using a diode array.

At the University of Arizona a research project is underway which addresses consistent color and consistent gray-scale reproduction for digital color displays used in medical image interpretation, specifically for Pathology. Now the University of Arizona can enter the field of ICC Profiling and Color Management. Verification of PerfectLum Software was successful. FIT and LUM tests were performed to verify the conformance and the deviation was quantified. The maximum GSDF Error is about 5.968 %. With respect to the results, all three objectives were met and the PerfectLum calibrated display confirmed to the AAPM TG18 standards.