DEPTH DISTRIBUTIONS OF RBE-WEIGHTED DOSE AND PHOTON-ISOEFFECTIVE DOSE FOR BORON NEUTRON CAPTURE THERAPY
DEPTH DISTRIBUTIONS OF RBE-WEIGHTED DOSE AND PHOTON-ISOEFFECTIVE DOSE FOR BORON NEUTRON CAPTURE THERAPY
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DOI：
10.1093/rpd/ncy235
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发表时间：
2019-05-01
影响因子：
1
通讯作者：
Hamada, Nobuyuki
中科院分区：
文献类型：
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作者：
Sato, Tatsuhiko;Masunaga, Shin-ichiro;Hamada, Nobuyuki
为表达硼中子俘获治疗（BNCT）的高相对生物学效应（RBE），提出了两种用于BNCT治疗计划的剂量。一方面，RBE加权剂量是BNCT各剂量分量按固定RBE加权的吸收剂量之和。另一方面，光子等效剂量是考虑到RBE的剂量依赖性和不同类型辐射之间的协同效应而计算的产生相同生物效应的光子剂量。在这项研究中，两种类型的剂量的深度分布的体模放置在加速器为基础的BNCT领域使用粒子和重离子传输代码系统，PHITS，加上扩展的随机微剂量动力学模型计算。与相应的RBE加权剂量相比，计算的光子等效剂量在低吸收剂量时较大，在高吸收剂量时较小，主要是由于考虑了RBE的剂量依赖性。此外，我们的计算表明，细胞间B-10浓度的大的变化大大降低了光子等效剂量。这些结果表明，考虑到RBE的剂量依赖性以及B-10分布的细胞间异质性，BNCT的生物效应的精确估计是必不可少的。
Two types of dose were proposed for use in the treatment planning of boron neutron capture therapy (BNCT) for expressing its high relative biological effectiveness (RBE). On one hand, the RBE-weighted dose is the sum of the absorbed doses weighted by fixed RBE for each dose component of BNCT. On the other hand, photon-isoeffective dose is the photon dose to give the same biological effect calculated considering the dose dependence of RBE and the synergetic effect between different types of radiation. In this study, the depth distributions of the two types of dose in a phantom placed at an accelerator-based BNCT field were calculated using Particle and Heavy Ion Transport code System, PHITS, coupled with an extended stochastic microdosimetric kinetic model. Compared with the corresponding RBE-weighted dose, the calculated photon-isoeffective dose was larger at lower absorbed dose and was smaller at higher absorbed dose, primarily due to the consideration of the dose dependence of RBE. In addition, our calculation revealed that the large variance of the intercellular B-10 concentration greatly reduces the photon-isoeffective doses. These results suggest that the considerations of the dose dependence of RBE as well as the intercellular heterogeneity in B-10 distribution are indispensable for the precise estimate of the biological effect of BNCT.