Assessment of flat panel LCD primary class display performance based on AAPM TG 18 acceptance protocol

Abstract

The image display is an important component of the Picture Archiving and Communication System (PACS) and of digital imaging in general. In this paper, we assess the display performance of 32 different flat panelLCD devices, in terms of their reflection, luminance response, luminance uniformity, resolution, noise, veiling glare and color uniformity included in the tentative guidelines of the AAPM TG18 document version 8.1. We also report on the angular dependencies of luminance and contrast, which constitute one of the miscellaneous tests. The tools used included a telescopic photometer, which was also used as a colorimeter, an illuminance meter, light sources for the reflection assessment, light-blocking devices, and digital TG18 test patterns. The luminance ratio (LR), maximum luminance difference (ΔLmax) and deviation of contrast response with respect to that of DICOM GSDF were 379.2±61.0, 1.6±1.1%, and 4.84±0.58%, respectively. The maximum luminance nonuniformity was 9.2±3.9% for the 10% luminance of the TG18-UNL10 test pattern. In the luminance-based resolution test, the percent luminance difference (ΔL) at the center was 0.78±0.42%. In all cases of noisetesting, the rectangular target in each square in the three quadrants was visible, as were all 15 targets, except for the smallest one, in each corner pattern and the center pattern. The glare ratio (GR) was 2350±1460. The average color uniformity parameter, Δ(u′,v′), across the display area of each display device was 0.002±0.001. Nevertheless, not all of the color uniformity parameters of the display devices associated with a workstation met the acceptance criteria. For 7 selected flat panel displays, the mean specular and diffuse reflection coefficients were 0.0061±0.0010 and 0.0017±0.0005 cd/m2 per lux, respectively. All of the test results conformed to the criteria recommended by AAPM TG18, indicating that the displays were fully acceptable for diagnosticimage interpretation. The maximum viewing angle conforming to the DICOM 3.14 standard luminance responses with a 10% tolerance was found to be approximately 50° in both directions along the vertical axis, 10° in the upper direction and 20° in the lower direction along the horizontal axis, and 20° in the upper direction and 10° in the lower direction along the diagonal axis. Therefore, a radiologist should interpret a displayed image by considering the physical characteristics of the narrow viewing angle of the AMLCD displays. The acceptance testing protocol described herein demonstrates the successful clinical implementation of the guidelines for the viewing conditions of medical displays, and if implemented with a QC program, can be used to determine when LCD devices used for diagnostic interpretation need to be upgraded.