Quality Control evaluation of 37 liquid crystal displays used in diagnostic services

摘要

The performance of 37 primary class liquid crystal display devices (2, 3 and 5 Mpixel matrix size) used in 9 different diagnostic services in Spain has been determined in terms of 13 quantitative and visual evaluations. The equipment had never been subjected to calibration or to QC tests since commissioning by vendors, between 2 and 18 months before measurements. Tests, using calibrated luminance meters and TG 18 patterns, have evaluated ambient light conditions and other basic performance indicators, namely, display geometric distortion, artefacts, resolution and low-contrast visibility, contrast luminance response compliance to DICOM standard, luminance extreme values and uniformity between pairs of monitors associated to a same workstation. The principal sources of non-compliance are failures to visualize low-contrast test objects (73% of displays), excessive differences with the DICOM contrast response standard (57%), and nonuniform response of monitor pairs (54%). Also, 43% of LCD were found located in places with excessive illumination and presenting specular reflections from faceplates. The analysis of ten 5 Mpixel displays, of possible use in mammography services, indicates similar performance as the rest of monitors, except for the ambient luminance (100% complying with recommendations) and larger non-compliance with the DICOM response standard (80%). No correlation between image quality indicators and monitor hours of operation was found.