The DICOM Gray Scale Display Function (GSDF) relates display contrast to the contrast threshold derived from the Barton Model (C_BM) of the human visual system. We have measured the contrast threshold (C_T) using a monochrome medical LCD monitor and graphics card under the conditions defined by the DICOM standard and compared the results to the Barten Model. A two Alternative Forced Choice (2AFC) observer performance test was used to measure contrast threshold. The 2AFC tests were given once to a large group of observers with varied medical imaging experience. A small subset of this group was tested multiple times over several months in order to examine intraobserver variability. The mean relative contrast (C_T/C_BM) associated with a 75% detection rate was found to be 0.508, with a standard deviation of 0.176. For the intraobserver tests, results improved after the first 3 trials. The mean C_T/C_BM values (and standard deviation) for the next 9 tests were 0.0980 (0.107), 0.244 (0.0928), and 0.398 (0.0855). The results indicate that contrast substantially less than 1 C_T/C_BM is detected based on the statistical criteria used. This can be explained based on the criteria for detection used in the classical observer tests that form the basis for the Barten model. Additionally, our data indicates significant differences amongst observers.

Date Published: 4 May 2004
PDF: 9 pages
Proc. SPIE 5372, Medical Imaging 2004: Image Perception, Observer Performance, and Technology Assessment, (4 May 2004); doi: 10.1117/12.537079

Published in SPIE Proceedings Vol. 5372:
Medical Imaging 2004: Image Perception, Observer Performance, and Technology Assessment
Dev P. Chakraborty; Miguel P. Eckstein, Editor(s)