Variations in Performance of LCDs Are Still Evident After DICOM Gray-Scale Standard Display Calibration

Abstract

Quality assurance in medical imaging is directly beneficial to image quality. Diagnostic images are frequently displayed on secondary-class displays that have minimal or no regular quality assurance programs, and treatment decisions are being made from these display types. The purpose of this study is to identify the impact of calibration on physical and psychophysical performance of liquid crystal displays (LCDs) and the extent of potential variance across various types of LCDs. Three display types were evaluated from Hewlett Packard, Viewsonic, and NEC, which totalled 36 LCDs. These displays were calibrated to the DICOM gray scale standard display function using a VeriLum photometer and associated software under the same ambient room conditions. The American Association of Physicists in Medicine Task Group 18 test patterns were used to measure minimum and maximum luminance, contrast ratios, luminance response, veiling glare (physical and psychophysical), psychophysical noise, spatial resolution, and display uniformity. Improvements after calibration were noted in all display types for luminance response and psychophysical evaluations of veiling glare. Minimum luminance, contrast ratios, and display uniformity improvements were noted in two separate display types. The only significant reduction in performance was noted for physical evaluations of veiling glare. The data presented show that calibration has a significant impact on the brightness and contrast of displays, and other display parameters are influenced by this. The amount of variation in performance that was still evident after calibration is of concern.