Radiation-shielding of healthy tissue is mandatory in breast intraoperative electron radiotherapy (IOERT). In this regard, dedicated radioprotection disks have been introduced. The aim of this study was to evaluate and compare the performance of three radioprotection disks widely used for breast IOERT. A Monte Carlo simulation approach was used for this purpose. The considered disks included Al + Pb, PMMA + Copper, and PTFE + Steel. They were stimulated by means of the MCNPX Monte Carlo code at depths around R100 and R90 of different electron energies in a water phantom, and their impact on the dosimetric properties of the therapeutic beam was evaluated in both correct and upside down disk placements. The electron energy spectrum immediately above and below each disk was calculated and analyzed. Furthermore, performance characteristics of the studied disks such as backscatter factors (BSFs) and transmission factors (TFs) at different electron energies were determined and compared. The results show that the Al + Pb disk most effectively attenuates the beam, while at the same time exhibits maximum BSF values. Employing the PMMA + Copper disk can minimize the BSF value but at the expense of an increased TF. The Al + Pb disk showed the best performance from the radiation protection viewpoint, while its highest BSF values could lead to perturbation of dose homogeneity within the target volume. PTFE + Steel disk showed an intermediate performance regarding the electron backscattering and transmission among the studied disks. The reverse placement of each disk can substantially increase the BSF value as compared to the correct situation but had less impact on the TF value.

中文翻译：

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比较某些专用的放射防护盘在乳房术中电子放射治疗中的性能：蒙特卡洛研究。

乳房术中电子放疗（IOERT）必须对健康组织进行辐射屏蔽。在这方面，已经引入了专用的防辐射盘。这项研究的目的是评估和比较三种广泛用于乳房IOERT的放射防护盘的性能。为此使用了蒙特卡洛模拟方法。所考虑的磁盘包括Al + Pb，PMMA +铜和PTFE +钢。它们通过MCNPX蒙特卡罗代码在水模型中不同电子能量的R100和R90附近的深度受到刺激，并在正确和上下颠倒的磁盘放置中评估了它们对治疗束剂量特性的影响。计算并分析了每个磁盘正上方和正下方的电子能谱。此外，确定并比较了所研究磁盘的性能特征，例如在不同电子能量下的背向散射因子（BSF）和传输因子（TFs）。结果表明，Al + Pb圆盘最有效地衰减了光束，同时展现出最大的BSF值。使用PMMA +铜盘可以最大程度地降低BSF值，但要以增加TF为代价。从辐射防护的角度来看，Al + Pb圆片表现出最佳性能，而其最高BSF值则可能导致目标体积内剂量均匀性的扰动。PTFE +钢盘在所研究的盘之间显示出关于电子反向散射和传输的中间性能。