Evaluation of depth dose and glandular dose for digital mammography

The purpose of this study is to evaluate the depth dose and mean glandular dose for the latest digital mammography. Depth doses were measured using GR-200F thin-film TLDs comprising LiF:Mg,Cu,P over three kinds of composition of mammographic phantom (glandular/fat: 30/70; 50/50; 70/30) under automatic exposure control by a digital mammographic unit (Novation DR, Siemens). Mean glandular doses were derived from entrance surface doses which were measured according to the Mammography Quality Control Manual of American College of Radiology. Two types of mean glandular dose calculation system were used and compared in this study. The depth dose could be established with thin-film TLDs and fitted by the model considered the primary and scatter radiation. The 50% depth dose falls at a depth of between 0.62 and 1.71 cm, which can represent the beam quality of X-ray spectra. The MGD calculated by Dance's method is 9-21% higher than that by Wu's method. Therefore, the difference should be considered by the Taiwan's regulation for Novation DR digital mammographic units.