Storage phosphor and film-screen mammography: performance with different mammographic techniques

Abstract.

The aim of this study was to compare the image quality of storage phosphor plates with that in screen-film radiograms in mammography. Two anode/filter combinations were also compared – Mo/Mo and W/Rh. S Storage phosphor plates, generation IIIN (Fuji, Tokyo, Japan) and a conventional screen-film system (Kodak, Rochester, N. Y.) were evaluated using two mammographic units. One unit had a 0.6-mm focal spot, an anode/filter combination of Mo/Mo and no grid (A_Mo); the other had a 0.3-mm focal spot, a grid, and two possible combinations of anode/filter Mo/Mo (B_Mo) and W/Rh (B_W). Simulated tumours and microcalcifications were randomly positioned in an anthropomorphic breast phantom (RMI model 165, no. 210–009, Radiation Measurements Inc., Middleton, Wisconsin). The image quality was evaluated using a modified version of receiver operating characteristics analysis. Five observers evaluated 300 films and 300 hard copy images each. Radiation doses were also determined. The image quality of the conventional screen-film images was significantly better than that for the storage phosphor plate mammograms. The B_Mo system rated best, for the detection of both tumours and microcalcifications, although it was not significantly different from the B_W system. Systems B_Mo and B_W rated significantly better than the A_Mo system for both image receptors studied. The mean absorbed dose was twice as high for the B_Mo system as for the A_Mo and B_W systems for both conventional and digital technique. The mammograms produced with the screen-film combination gave a significantly better detectability than the storage phosphor plates used in this study. Substantial dose reduction could be achieved using an anode/filter combination of W/Rh instead of Mo/Mo with no significant loss of information in the images.