AbstractID: 7666 Title: A quality index for the quality of softcopy display in PACS?
A quality index for the quality of softcopy display in PACS?
Jihong Wang, Ph.D.
Radiology Department
University of Texas Southwestern Medical Center
Dallas, Texas 75390-9071
It has been known that contrast sensitivity of human viewer depends on many factors such as the brightness
of the target and its surroundings. This fact has made the judgement of softcopy display quality more
complex. For instance, a softcopy display may have better performance at higher luminace areas while
another may be better at darker areas for a radiographic image. Based on the contrast threshold
measurements using an interactive tool on several softcopy display devices, a strong correlation was found
between the slope of the Look-Up table (LUT) and the contrast threshold. Also a cutoff value in the slope
was found that when the slope at any point on the LUT is larger than this value, the contrast threshold
becomes one digital input value. In other words, all inherent contrast contained in the digital image should
be visible if proper adaptation is achieved by the viewer. In addition, based on this finding and the digital
nature of the images displayed on monitors one can calculate the required maximum to minimum
luminance ratio on monitors in order to make all contrasts visible.