Physics Department, Hakim Sabzevari University, Sabzevar, Iran.
Medical Physics and Radiological Sciences Department, Sabzevar University of Medical Sciences, Sabzevar, Iran.
Radiat Environ Biophys. 2020 May;59(2):265-281. doi: 10.1007/s00411-020-00836-z. Epub 2020 Apr 6.
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 R and R 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.
健康组织的辐射防护在术中电子放射治疗（IOERT）中是强制性的。为此，已经引入了专用的放射防护盘。本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。为此目的使用了蒙特卡罗模拟方法。所考虑的磁盘包括 Al+Pb、PMMA+铜和 PTFE+钢。在水模体中，用 MCNPX 蒙特卡罗代码在 R 和不同电子能量的 R 附近的深度对这些磁盘进行了模拟，并评估了它们在正确和颠倒的磁盘放置方式下对治疗束剂量特性的影响。计算并分析了每个磁盘上方和下方的电子能谱。此外，还确定并比较了研究磁盘的性能特征，例如不同电子能量下的反向散射因子（BSF）和传输因子（TF）。结果表明，Al+Pb 磁盘最有效地衰减了射束，同时表现出最大的 BSF 值。使用 PMMA+铜磁盘可以最小化 BSF 值，但代价是 TF 值增加。从辐射防护的角度来看，Al+Pb 磁盘的性能最好，但其最高的 BSF 值可能会导致靶区内部剂量均匀性的波动。PTFE+钢磁盘在研究磁盘的电子反向散射和传输方面表现出中等性能。与正确情况相比，每个磁盘的反向放置会大大增加 BSF 值，但对 TF 值的影响较小。
