Digital Breast Tomosynthesis: Three-Dimensional Measurement of Breast-Absorbed Dose Distribution

BACKGROUND: The dose exposure associated with digital breast tomosynthesis (DBT) is evaluated by multiplying the mean glandular dose (MGD) of mammography (MMG) with the correction coefficient of the angle of X-ray incidence. However, it has been pointed out that there are various problems when using the MGD as a standard for risk assessment in breast cancer screening. Therefore, the aim of this study was to assess the breast-absorbed dose for different breast sizes for dose assessment. Furthermore, in this study, by measuring the dose distribution three-dimensionally, we aimed to examine the MGD correction method using the breast size as a factor. METHODS: A simulated breast phantom with a diameter of 40–160 mm and a total thickness of 40 mm, made with polymethyl methacrylate, was created by simulating the phantom shape used in the simulation calculation for calculating the MGD. It was made with polymethyl methacrylate. Radiochromic films were placed at different depths, which measured the breast-absorbed dose distribution three-dimensionally. The MGD was calculated from the breast-absorbed dose distribution obtained. RESULTS: The three-dimensional dose distribution revealed that there was a difference in the distribution of MMG and DBT with increasing depth. In addition, a lower X-ray energy and a smaller breast size resulted in a greater difference in the absorbed dose between DBT and MMG. CONCLUSION: Incorporating the DBT correction according to the breast size into the MGD improves the accuracy of dose evaluation by the MGD. Additionally, a corrected MGD provides useful information for risk assessment when DBT is used for breast cancer screening.