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Mammography phantom utilizing free-response receiver operating characteristic methodology

We have developed a mammography phantom which is designed to take advantage of the recently developed Free-Response Receiver Operating Characteristic (FROC) methodology. This observer performance methodology allows for multiple abnormalities and observer responses per image and requires both detection and correct localization for a true positive event. The phantom is composed of several Lucite slabs and a series of 30 test plates to which were affixed simulated microcalcifications, fibrils and masses. The phantom also simulated a structured background. The series was radiographed using three different techniques (30 kVp with no grid, 28 kVp and 35 kVp). These three sets of 30 images were viewed by three medical physicists and one radiologist in the FROC manner. The analysis provided an index of performance for each reader and each set. As multiple abnormalities may appear on a single image, good statistics are achieved using relatively few images. Statistical comparison of the index values indicates that, with improvements in the phantom, the combination of the phantom with FROC methodology should be capable of detecting subtle changes in image quality and may be used on a regular basis as part of a detailed quality assurance program.