Tanaka Kenichi, Kobayashi Tooru, Bengua Gerard, Nakagawa Yoshinobu, Endo Satoru, Hoshi Masaharu
Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
Phys Med Biol. 2005 Jan 7;50(1):167-77. doi: 10.1088/0031-9155/50/1/013.
The dependence of boron-dose enhancer (BDE) characteristics on dose protocol and 10B concentration was evaluated for BNCT using near-threshold 7Li(p,n)7Be direct neutrons. The treatable protocol depth (TPD) was utilized as an evaluation index. MCNP calculations were performed for near-threshold 7Li(p,n)7Be at a proton energy of 1.900 MeV and for a polyethylene BDE. The effect of dose protocol on BDE characteristics was reflected in terms of the optimum BDE thickness needed for maximum TPD which was found to be independent of the treatable dose but was observed to vary for different combinations of the tolerance doses for heavy charged particles and gamma rays. For the 10B concentration dependence, the TPD was increased by increasing the T/N ratio, i.e., the ratio of the 10B concentration in the tumour (10B(Tumour)) to that in the normal tissue (10B(Normal)), and by increasing 10B(Tumour) and 10B(Normal) at constant T/N ratio. It was found that the use of BDE becomes unnecessary from the viewpoint of increasing the TPD, when 10B(Tumour) is over a certain level which is decided by the conditions of the dose protocol.
使用近阈能7Li(p,n)7Be直接中子进行硼中子俘获疗法（BNCT）时，评估了硼剂量增强剂（BDE）特性对剂量方案和10B浓度的依赖性。将可治疗方案深度（TPD）用作评估指标。针对质子能量为1.900 MeV的近阈能7Li(p,n)7Be以及聚乙烯BDE进行了蒙特卡罗N粒子输运代码（MCNP）计算。剂量方案对BDE特性的影响体现在最大TPD所需的最佳BDE厚度方面，发现其与可治疗剂量无关，但对于重带电粒子和γ射线的耐受剂量的不同组合，该厚度会有所变化。对于10B浓度依赖性，通过增加T/N比（即肿瘤中10B浓度（10B(肿瘤)）与正常组织中10B浓度（10B(正常)）之比）以及在恒定T/N比下增加10B(肿瘤)和10B(正常)，TPD会增加。结果发现，当10B(肿瘤)超过由剂量方案条件决定 的某个水平时，从增加TPD的角度来看，使用BDE变得不必要。
