Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, Ibaraki Prefecture, Japan.
Asian Pac J Cancer Prev. 2023 Mar 1;24(3):953-960. doi: 10.31557/APJCP.2023.24.3.953.
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.
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.
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.
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.
数字乳腺断层摄影术（DBT）的剂量暴露通过将乳腺摄影（MMG）的平均腺体剂量（MGD）乘以射线入射角度的校正系数来评估。然而，已经指出，在使用 MGD 作为乳腺癌筛查风险评估的标准时存在各种问题。因此，本研究旨在评估不同乳房大小的乳腺吸收剂量以进行剂量评估。此外，在本研究中，通过三维测量剂量分布，我们旨在检查使用乳房大小作为因素的 MGD 校正方法。
使用聚甲基丙烯酸甲酯模拟直径为 40-160 毫米且总厚度为 40 毫米的模拟乳房体模，该体模模拟了用于计算 MGD 的模拟计算中使用的模拟体模形状。使用聚甲基丙烯酸甲酯制造。放置在不同深度的放射色胶片三维测量乳腺吸收剂量分布。从获得的乳腺吸收剂量分布中计算出 MGD。
三维剂量分布表明，随着深度的增加，MMG 和 DBT 的分布存在差异。此外，较低的 X 射线能量和较小的乳房尺寸导致 DBT 和 MMG 之间的吸收剂量差异更大。
将根据乳房大小的 DBT 校正纳入 MGD 可以提高 MGD 剂量评估的准确性。此外，校正后的 MGD 为使用 DBT 进行乳腺癌筛查时的风险评估提供了有用的信息。
