Tanaka Kenichi, Kobayashi Tooru, Sakurai Yoshinori, Nakagawa Yoshinobu, Ishikawa Masayori, Hoshi Masaharu
Department of Nuclear Engineering. Kyoto University, Japan.
Phys Med Biol. 2002 Aug 21;47(16):3011-32. doi: 10.1088/0031-9155/47/16/315.
A calculation method for the dosage of neutrons by near-threshold 7Li(p, n)7Be and gamma rays by 7Li(p, p'gamma)7Li was validated through experiments with variable distance between the Li target and the phantom, focusing on large angular dependence. The production of neutrons and gamma rays in the Li target was calculated by Lee's method and their transport in the phantom was calculated using the MCNP-4B code. The dosage in intra-operative boron neutron capture therapy (BNCT) using near-threshold 7Li(p, n)7Be direct neutrons was evaluated using the validated calculation method. The effectiveness of the usage of the direct neutrons was confirmed from the existence of the region satisfying the requirements of the protocol utilized in intra-operative BNCT for brain tumours in Japan. The boron-dose enhancer (BDE) introduced in this paper to increase the contribution of the 10B(n, alpha)7Li dose in the living body was effective. The void utilized to increase the dose in deep regions was also effective with BDE. For the investigation of 1.900 MeV proton beams, for example, it was found that intraoperative BNCT using near-threshold 7Li(p, n)7Be direct neutrons is feasible.
通过在锂靶与体模之间改变距离进行实验，验证了一种通过近阈7Li(p, n)7Be反应计算中子剂量以及通过7Li(p, p'γ)7Li反应计算γ射线剂量的方法，重点关注大角度依赖性。利用Lee方法计算锂靶中中子和γ射线的产生，并使用MCNP - 4B代码计算它们在体模中的输运。采用经过验证的计算方法评估了术中使用近阈7Li(p, n)7Be直接中子进行硼中子俘获治疗（BNCT）时的剂量。从存在满足日本脑肿瘤术中BNCT所采用方案要求的区域，证实了直接中子使用的有效性。本文引入的硼剂量增强剂（BDE）可增加活体中10B(n, α)7Li剂量的贡献，是有效的。用于增加深部区域剂量的空隙配合BDE也有效。例如，对于1.900 MeV质子束的研究发现，术中使用近阈7Li(p, n)7Be直接中子进行BNCT是可行的。
