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The detectability of malignant tumor-derived microcalcifications with conventional mammography was compared to that with digital images (2000×2510 pixels by 10 bits) derived from a storage phosphor–based digital radiography system capable of 5 line pair/mm resolution at identical exposure factors (30 kVp, 250 mAs, 65 cm film–focus distance). Microcalcifications (50–800 microns in diameter) were randomly superimposed on a preserved human breast specimen. ROC analysis based on 480 observations made by four readers indicated that the ability to detect the calcifications with digital images (ROC area=0.871 ± 0.066) was equivalent to conventional mammography (ROC area=0.866 ± 0.075) despite lower spatial resolution. With digital mammography, 62% of all clusters were correctly localized, but only 23.6% of the individual calcifications were counted. With conventional mammography 61% of all clusters were correctly localized, but significantly more of the individual calcifications (31.5%) were counted.