Influence of film and monitor display luminance on observer performance and visual search

The purpose of this study was to measure the influence of display luminance on detection performance and visual search behavior. The results of the study should be helpful in establishing minimally acceptable display conditions for viewing radiographs on cathode-ray tube (CRT) monitors.

Two groups of six radiologists each viewed 50 pairs of mammograms. One group viewed film images on a standard mammographic view box; the other viewed images on a high-resolution CRT monitor. Two luminance levels were studied for each display type. Observers reported on the presence or absence of masses or microcalcification clusters and on their confidence in that decision. Confidence data were analyzed by using alternative free-response receiver operating characteristic (AFROC) techniques. Eye position also was recorded as observers viewed the images.

For both the film and monitor studies, detection performance (AFROC area under the curve) was not affected significantly by display luminance, but search behavior was. Total viewing and decision dwell times were shorter with the higher-luminance displays, especially for true-negative decisions. Significantly more fixation clusters were generated during the search of lesion-free than of lesion-containing images with the lower-luminance displays.

Display luminance affects visual search performance with both film and monitor displays without affecting detection performance significantly. Higher-luminance displays yield more efficient search performance. The true-negative dwell times and number of clusters are suggestive that lower-luminance levels prolong the search and recognition of normal, lesion-free areas compared with lesion-containing areas.