Computed radiography versus screen-film mammography in detection of simulated microcalcifications: A receiver operating characteristic study based on phantom images

The authors compare a 43 μm computed radiographic system with a mammographic screen-film system for detection of simulated microcalcifications in an observer performance study. The task of detecting microcalcifications was simulated by imaging aluminum wire segments (200–500 μm in length; 100, 125, or 150 μm in diameter) that overlapped with tissue background structures produced by beef brisket. A total of 288 such simulations were generated and examined with both computed radiography and conventional screen-film mammography techniques. Computed radiography was performed with high-resolution plates, a 43-μm image reader, and a 43-μm laser film printer. Computed radiographic images were printed with simple contrast enhancement and compared with screen-film images in a receiver operating characteristic study in which experienced reader detected and scored the simulated microcalcifications. Observer performace was quantitated and compared by computing the area under the receiver operating characteristic curve. Although the resolution of the computed radiography system was better than that of commercial systems, it fell short of that of screen-film systems. For the 100-μm microcalcifications, the difference in the average area under the curve was not statistically significant, but it was significant for the larger simulated microcalcifications: the average area under the curve was 0.58 for computed radiography versus 0.76 for screen-film imaging for the 125-μm microcalcifications and 0.83 versus 1.00, respectively, for the 150-μm microcalcifications. Observer performance in the detection of small simulated microcalcifications (100–150 μm in diameter) is better with screen-film images than with high-resolution computed radiographic images.