A Performance Metric for Evaluating Conformanceof Medical Image Displays with the ProposedACR/NEMA Display Function Standard

ACR/NEMA (now DICOM) has released for public comment the Display Function Standard document. This standard, produced by ACR/NEMA Working Group XI, has been developed in order to solve the problem of standardizing the response of grey scale display systems . This paper presents a methodology proposed in the Display Function Standard for quantitatively calculating the conformance of a display device to the Standard Display Function based on statistical measures, which are referred to as the linearization uniformity measure s (LUM). There are two LUM measures, R2, or global uniformity, and Root Mean Square Error (RMSE), or local uniformity . The derivation of both measures is described. Two additional measures that provide a better description of the achievable dynamic range of a display device than simply its luminance range are also described, the theoretical number of Just Noticeable Differences (JNDS) of the display, and the realized number of JNDS of the display. Currently available medical image display systems are analyzed using each of these measures, to examine their shortcomings, and suggest what changes might be desirable in the design of medical image display systems in the future.