Dosimetric considerations in mammography

The aim of this study was to measure the absorbed dose to seven organs othe r than the breast in mammography in order to calculate their contribution t o the effective dose. The absorbed dose to these organs was measured using a lucite upper body anthropomorphic phantom, containing thermoluminescent d osimeters (TLD) at appropriate locations, exposed as in a mammographic exam ination. In addition, the dependence of the absorbed dose on kVp, mAs and b reast thickness was examined. The absorbed dose due to scattered radiation was found to be negligible to all organs except to the sternum red bone mar row (SRBM) and the thyroid. The mean doses to the SRBM and the thyroid, for a set of four exposures, one craniocaudal and one 90 degrees mediolateral per breast, simulating a complete breast screening examination, varied betw een 0.40 and 1.27 and 0.05-0.17 mu Gy mAs(-1), respectively, depending on t he breast thickness and the kVp selection. Effective dose from mammography was also calculated based on the absorbed dose to the breast, the SRBM and the thyroid and tissue-weighting factors. The effective dose was found to v ary between 0.66 and 0.85 mu Sv mAs(-1) depending on the breast thickness a nd the kVp value selected. The radiation dose to the breast contributes ove r 98% to the effective dose.