Detection of subtle microcalcifications: comparison of computed radiography and screen-film mammography

Observer performance tests were conducted to compare the effects of image-processing technique (unsharp mask filtering) on the diagnostic accuracy of computed radiography (CR) with storage phosphors in the detection of microcalcifications. Comparison of detectability of microcalcifications with CR and with screen-film mammography was also performed. Clusters of microcalcifications (125-250 microns in diameter) were randomly superimposed on human breast specimens. Observer performance tests were carried out with receiver operating characteristic (ROC) analysis. The area under the ROC curve and the cumulative true-positive-localization fraction were both used as indexes of performance. Observer performance experiments with nine observers indicated that the two types of screen-film images used provided higher detectability than the CR images. The detectability of microcalcifications on the CR images improved slightly with use of the unsharp masking technique. However, no statistically significant difference was found between processed and unprocessed CR images, and detectability still did not reach the level achieved with the screen-film images.