The mean glandular dose (MGD) is the most suitable dosimetric quantity used in mammography to describe the absorbed dose by the breast, although it cannot be directly acquired. Studies have provided conversion factors widely implemented in international dosimetry protocols to estimate MGD, such as normalized glandular dose (DgN). Over time, the DgN estimation was refined by considering geometric models that approach a real clinical environment, such as new anode/filter combinations, compression plate and breast models. However, there is no detailed study of how the bucky (support plate, antiscatter grid and detector) can affect the DgN estimation. A modified PENELOPE Monte Carlo code was used for DgN estimation. The irradiation geometric model was built as a complete digital mammography system, considering a homogeneous breast and different typical bucky models in commercial mammography units. Simulations were carried out for mono and polyenergetic beams considering different imaging geometries. Studies with monoenergetic beams showed that the bucky presence affected DgN mainly for higher beam energies and thinner breasts. The breast support plate was the bucky component that most affected the DgN, followed by the antis-scatter grid and finally, the image detector. Studies with polyenergetic conventional (low-energy) spectra showed that the bucky exerted a minimal influence on DgN values (less than 1.0%). For high-energy spectra, mainly employed in modalities such as contrast-enhanced digital mammography, the DgN values were more affected by the bucky, increasing by 4.8% the DgN values for a 2 cm thick breast and a W/Cu 50 kV spectrum. Bucky inclusion in computer simulations is highly recommended mainly for thinner breasts and high-energy spectra. To simplify the simulations, we confirm that a homogeneous carbon fibre block support, with thickness between 3.9 and 4.1 mm, can be used as a good substitute for a complete bucky model.

中文翻译：

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数字乳腺X线摄影中巴基成分对标准化腺体剂量估计影响的计算评估

平均腺体剂量（MGD）是乳房X线照相术中最适合描述乳房吸收剂量的剂量学量，尽管它不能直接获得。研究提供了在国际剂量测定方案中广泛应用的转换因子来估计 MGD，例如标准化腺体剂量 (DgN)。随着时间的推移，通过考虑接近真实临床环境的几何模型（例如新的阳极/过滤器组合、压缩板和乳房模型），DgN 估计得到了完善。然而，目前还没有关于巴基（支撑板、防散射网格和探测器）如何影响 DgN 估计的详细研究。修改后的 PENELOPE Monte Carlo 代码用于 DgN 估计。考虑到商业乳房X光检查装置中的同质乳房和不同的典型巴基模型，将辐射几何模型构建为完整的数字乳房X光检查系统。考虑不同的成像几何形状，对单能光束和多能光束进行了模拟。单能光束的研究表明，巴基的存在对 DgN 的影响主要在于更高的光束能量和更薄的乳房。乳房支撑板是对 DgN 影响最大的巴基组件，其次是防散射网格，最后是图像检测器。多能常规（低能）光谱研究表明巴基对 DgN 值的影响很小（小于 1.0%）。对于主要用于对比增强数字乳房 X 线摄影等模式的高能光谱，DgN 值受巴基影响更大，对于 2 cm 厚的乳房和 W/Cu 50 kV 光谱，DgN 值增加了 4.8%。强烈建议在计算机模拟中加入巴基，主要针对较薄的乳房和高能谱。为了简化模拟，我们确认厚度在 3.9 至 4.1 毫米之间的均质碳纤维块支撑可以用作完整巴基模型的良好替代品。