COMPUTED RADIOGRAPHY VERSUS SCREEN-FILM MAMMOGRAPHY IN DETECTION OF SIMULATED MICROCALCIFICATIONS - A RECEIVER OPERATING CHARACTERISTIC STUDY BASED ON PHANTOM IMAGES

Rationale and Objectives. The authors compare a 43-mu m computed radio graphic system with a mammographic screen-film system for detection of simulated microcalcifications in an observer-performance study. Mater ials and Methods. The task of detecting microcalcifications was simula ted by imaging aluminum wire seg ments (200-500 mu m in length; 100, 1 25, or 150 mu m in diameter) that overlapped with tissue background st ructures produced by beef brisket. A total of 288 such simulations wer e generated and examined with both computed radiography and convention al screen-film mammography techniques. Computed radiography was perfor med with high-resolution plates, a 43-mu m image reader, and a 43-mu m laser film printer. Computed radiographic images were printed with si mple contrast enhancement and compared with screen-film images in a re ceiver operating characteristic study in which experienced readers det ected and scored the simulated microcalcifications. Observer performan ce was quantitated and compared by computing the area under the receiv er operating characteristic curve. Results. Although the resolution of the computed radiography system was better than that of commercial sy stems, it fell short of that of screen-film systems. For the 100-mu m microcalcifications, the difference in the average area under the curv e was not statistically significant, but it was significant for the la rger simulated microcalcifications: the average area under the curve w as 0.58 for computed radiography versus 0.76 for screen-film imaging f or the 125-mu m microcalcifications and 0.83 versus 1.00, respectively , for the 150-mu m microcalcifications. Conclusion. Observer performan ce in the detection of small simulated microcalcifications (100-150 mu m in diameter) is better with screen-film images than with high-resol ution computed radiographic images.