A perceptually tempered display for digital mammograms

The cathode ray tube of a workstation for use with digital mammograms was c alibrated with a photometer to produce an input-output characteristic curve similar to the perceptually linear curve defined by a current display stan dard. Then, a test pattern consisting of bars of increasing intensity conta ining disks of decreasing contrast was used by an observer to estimate the minimal detectable contrast (MDC) at different levels of display luminance. The MDC was modeled by a parabola. The shape of the parabola was determine d by the observer's perceptual responses, and the range was determined by t he maximum and minimum pixel values of the breast parenchyma, As each mammo gram was displayed, the contour of the breast was automatically found and p ixels within the breast image were sampled to determine the pixel values th at were used to compute the maximum and minimum pixel values. The parabola was integrated to determine the look-up table for the initial MDC-tempered display of the mammogram, Preliminary observer performance tests showed no significant differences in the accuracy and speed of three radiologists who read a set of mammograms when the MDC-tempered display was compared with t he perceptually linear display.