Microdosimetric quantities of an accelerator-based neutron source used for boron neutron capture therapy measured using a gas-filled proportional counter
Microdosimetric quantities of an accelerator-based neutron source used for boron neutron capture therapy measured using a gas-filled proportional counter
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DOI：
10.1093/jrr/rrz101
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发表时间：
2020-02
影响因子：
2
通讯作者：
N. Hu;Hiroki Tanaka;T. Takata;K. Okazaki;R. Uchida;Y. Sakurai
中科院分区：
文献类型：
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作者：
N. Hu;Hiroki Tanaka;T. Takata;K. Okazaki;R. Uchida;Y. Sakurai
摘要硼中子俘获治疗（BNCT）是一种新兴的放射治疗方式，具有选择性破坏癌细胞的潜力。目前，BNCT使用核反应堆进行。然而，未来的趋势是朝着在医院环境中使用的基于加速器的系统发展。典型的BNCT辐射场具有几种不同类型的辐射。应量化射束质量，以准确确定要输送到靶点的剂量。本研究利用组织等效正比计数器（TEPC）来测量基于加速器的中子源的微剂量和宏观剂量。与TEPC测量的微观和宏观剂量学量进行了比较，通过粒子和重离子输运代码系统（PHITS）的蒙特卡罗模拟。在空气中自由测量的>20 keV/μm事件1 h辐照的吸收剂量计算为1.31 ± 0.02戈伊。模拟结果为1.41 ± 0.07戈伊。实测值与计算值吻合良好。根据测得的微剂量谱评价的相对生物学有效性（RBE）计算为3.7 ± 0.02，与模拟值3.8 ± 0.1相似。这些结果表明，PHITS蒙特卡罗模拟可以准确地模拟微观和宏观剂量学量。RBE的计算使用单响应函数，结果与其他几个研究所使用类似的方法进行了比较。然而，在临床应用中使用这种单响应函数时必须小心，因为它仅对低剂量有效。对于临床剂量范围（即，高剂量），需要考虑目标内部的多事件分布。
Abstract Boron neutron capture therapy (BNCT) is an emerging radiation treatment modality, exhibiting the potential to selectively destroy cancer cells. Currently, BNCT is conducted using a nuclear reactor. However, the future trend is to move toward an accelerator-based system for use in hospital environments. A typical BNCT radiation field has several different types of radiation. The beam quality should be quantified to accurately determine the dose to be delivered to the target. This study utilized a tissue equivalent proportional counter (TEPC) to measure microdosimetric and macrodosimetric quantities of an accelerator-based neutron source. The micro- and macro-dosimetric quantities measured with the TEPC were compared with those obtained via the the particle and heavy ion transport code system (PHITS) Monte Carlo simulation. The absorbed dose from events >20 keV/μm measured free in air for a 1-h irradiation was calculated as 1.31 ± 0.02 Gy. The simulated result was 1.41 ± 0.07 Gy. The measured and calculated values exhibit good agreement. The relative biological effectiveness (RBE) that was evaluated from the measured microdosimetric spectrum was calculated as 3.7 ± 0.02, similar to the simulated value of 3.8 ± 0.1. These results showed the PHITS Monte Carlo simulation can simulate both micro- and macro-dosimetric quantities accurately. The RBE was calculated using a single-response function, and the results were compared with those of several other institutes that used a similar method. However, care must be taken when using such a single-response function for clinical application, as it is only valid for low doses. For clinical dose ranges (i.e., high doses), multievent distribution inside the target needs to be considered.