title: Viewing angle performance of medical liquid crystal displays.
abstract: Cathode-ray tube (CRT) and liquid crystal display (LCD) are currently two main technologies for displaying medical images. LCDs possess a number of advantages, but their performance varies as a function of viewing angle. Our purpose in this study was to characterize the angular response performance of five medical-grade LCDs, and to substantiate their impact on their compliance with the DICOM gray scale display function (GSDF). Furthermore, the study aimed to test a framework to define an angular acceptance range for medical LCDs based on the recent AAPM TG18 guidelines. Measurements were made on five calibrated dual-domain LCDs, including two 3 megapixel monochrome LCDs, two 5 megapixel monochrome LCDs, and one 9 megapixel color LCD. The luminance performance of each display device was measured as a function of the viewing angle at 17 discrete levels using TG18-LN test patterns and a Fourier-optics-based luminance meter. The luminance data were analyzed according to the AAPM TG18 methodology. The displays showed notable variation in luminance and contrast performance as a function of the viewing angle, particularly in diagonal viewing orientations. Overall, the luminance ratio remained greater than 175 within +/-20 degrees and +/-33 degrees viewing angle cones (beta175 = 20 degrees-33 degrees). Aiming to maintain a maximum deviation from the GSDF contrast less than 0.3, i.e., kappa17 < or = 0.3, acceptable viewing angle cones of +/-22 degrees and +/-35 degrees were indicated (alpha 0.3= 22 degrees-35 degrees). The findings demonstrate the significant impact of angular response on image contrast, and the utility of alpha 0.3 and beta175 quantities for defining the viewing angle cones within which a medical LCD device can be effectively utilized.
authors.affiliation: Duke Advanced Imaging Laboratories, Department of Radiology, Duke University, Durham, North Carolina 27710, USA.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Samei
authors.forename: Steven L
authors.initials: SL
authors.lastname: Wright
mesh_terms: D001610:Beta Particles; D002138:Calibration; D015350:Contrast Sensitivity; D003626:Data Display; D003952:Diagnostic Imaging / Q000295:instrumentation / Q000379:methods*; D008029:Lighting; D050866:Liquid Crystals; D049449:Luminescence; D055095:Optics and Photonics; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity