Image evaluation method for digital mammography with soft-copy reading using a digital phantom

ABSTRACT Mammograms are evaluated on soft-copy films or hard copies. In Japan, soft-copy diagnoses shift rapidly, and the method for facilities applying it is necessary for soft-copy diagnosis. Digital mammography has high resolution and a large matrix size. On a monitor, the image is either displayed partially at 1:1 pixel mapping or narrowed to fit the screen, resulting in loss of image quality. Therefore, we developed a digital phantom for soft-copy diagnosis in digital mammography.We developed the digital phantoms used by every mammographicdetector sold in Japan. For our digital phantom, we used C to create signals, which we converted to DICOM using Osirix. This phantom is like the Contrast Detail Phantom and comprises 12 different shapes and eight different brightness levels. It becomes one group of nine, and each signal is located at the prime number coordinate from a central signal coordinate. Visual evaluation refers to the visibility of the nine signal coordinates when the image is adjusted to fit the monitor’s display. A digital phantom is useful not only for evaluating display systems that feature reducing functions and monitor resolution but also for educational purposes such as confirming the effects of the monitor’s resolution and reducing functions as well as for precision management with regard to deterioration and malfunction. Although digital phantoms have been implemented at 120 facilities, at two other facilities, viewer problems were detected.