Effect of display luminance on the feature detection rates of masses in mammograms

Our purpose in this study was to determine the importance of the luminance range of the display system for the detection of simulated masses in mammog rams. Simulated masses were embedded in selected portions (512 x 512 pixels ) of mammograms digitized at 50 mu pixels, 12 bits deep. The masses were em bedded in one of four quadrants in the image. An observer experiment was co nducted in which the observer's task was to determine in which quadrant the mass is located. The key variables involved in each trial included the pos ition of the mass, the contrast level of the mass, and the luminance of the display. The contrast of the mass with respect to the background was fixed to one of four selected contrast levels. The digital images were printed t o film, and displayed on a mammography lightbox. The display luminance was controlled by placing neutral density films between the laser printed films of mammographic backgrounds and the lightbox. The resulting maximum lumina nces examined in this study ranged from 34 cd/m(2) to 2056 cd/m2. Twenty ob servers viewed 80 different images (20 observations at each of 4 different mass contrast levels) under each of the 5 luminance conditions for a total of 800 independent observations per observer. An analysis of variance yield ed no statistically significant correlation between the luminance range of the display and the feature detection rate of the simulated masses in mammo grams. However, the performance of the lower luminance display systems (les s than 300 cd/m(2)), may be reduced due to the high levels of ambient light found in many reading environments. (C) 1999 American Association of Physi cists in Medicine. [S0094-2405(99)01811-8].