Moghaddasi Leyla, Bezak Eva
Department of Physics, University of Adelaide, Adelaide, SA, Australia.
Department of Medical Physics, Adelaide Radiotherapy Centre, Adelaide, SA, Australia.
Australas Phys Eng Sci Med. 2018 Mar;41(1):129-141. doi: 10.1007/s13246-018-0617-z. Epub 2018 Jan 23.
Boron neutron capture therapy (BNCT) is a biochemically-targeted type of radiotherapy, selectively delivering localized dose to tumour cells diffused in normal tissue, while minimizing normal tissue toxicity. BNCT is based on thermal neutron capture by stable [Formula: see text]B nuclei resulting in emission of short-ranged alpha particles and recoil [Formula: see text]Li nuclei. The purpose of the current work was to develop and validate a Monte Carlo BNCT beam model and to investigate contribution of individual dose components resulting of neutron interactions. A neutron beam model was developed in Geant4 and validated against published data. The neutron beam spectrum, obtained from literature for a cyclotron-produced beam, was irradiated to a water phantom with boron concentrations of 100 μg/g. The calculated percentage depth dose curves (PDDs) in the phantom were compared with published data to validate the beam model in terms of total and boron depth dose deposition. Subsequently, two sensitivity studies were conducted to quantify the impact of: (1) neutron beam spectrum, and (2) various boron concentrations on the boron dose component. Good agreement was achieved between the calculated and measured neutron beam PDDs (within 1%). The resulting boron depth dose deposition was also in agreement with measured data. The sensitivity study of several boron concentrations showed that the calculated boron dose gradually converged beyond 100 μg/g boron concentration. This results suggest that 100μg/g tumour boron concentration may be optimal and above this value limited increase in boron dose is expected for a given neutron flux.
硼中子俘获疗法（BNCT）是一种生化靶向放疗方法，可将局部剂量选择性地传递至扩散于正常组织中的肿瘤细胞，同时将正常组织毒性降至最低。BNCT基于稳定的¹⁰B核俘获热中子，从而发射短程α粒子和反冲⁷Li核。当前工作的目的是开发并验证蒙特卡洛BNCT束流模型，并研究中子相互作用产生的各个剂量成分的贡献。在Geant4中开发了一个中子束流模型，并根据已发表的数据进行了验证。从文献中获取的回旋加速器产生的束流的中子束流能谱，被照射到硼浓度为100μg/g的水体模上。将体模中计算得到的百分深度剂量曲线（PDD）与已发表的数据进行比较，以在总剂量和硼深度剂量沉积方面验证束流模型。随后，进行了两项敏感性研究，以量化：（1）中子束流能谱，以及（2）各种硼浓度对硼剂量成分的影响。计算得到的和测量得到的中子束流PDD之间取得了良好的一致性（在1%以内）。由此产生的硼深度剂量沉积也与测量数据一致。对几种硼浓度的敏感性研究表明，计算得到的硼剂量在硼浓度超过100μg/g后逐渐收敛。这些结果表明，100μg/g的肿瘤硼浓度可能是最佳的，对于给定的中子通量，超过该值后硼剂量的增加有限。
