A Monte Carlo study for the calculation of the average linear energy transfer (LET) distributions for a clinical proton beam line and a radiobiological carbon ion beam line
A Monte Carlo study for the calculation of the average linear energy transfer (LET) distributions for a clinical proton beam line and a radiobiological carbon ion beam line
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DOI：
10.1088/0031-9155/59/12/2863
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发表时间：
2014-06-21
影响因子：
3.5
通讯作者：
Varisano, A.
中科院分区：
文献类型：
--
作者：
Romano, F.;Cirrone, G. A. P.;Varisano, A.
利用蒙特卡罗程序Geant 4（GEometry ANd Tracking）研究了质子和碳离子束的注量、深度吸收剂量和线性能量转移（LET）分布。开发了一个开源应用程序，旨在模拟两个典型的传输光束线，一个用于眼部治疗和质子细胞照射，另一个用于碳离子细胞照射。该工具允许评估初级和总剂量平均LET，并预测其在体素化或切片几何形状中的空间分布。为了真实地再现LET分布，计算中考虑了次级粒子对核相互作用的贡献。考虑到质子和碳离子束的原始和扩展布拉格峰，最大能量为62 MeV/n。深度剂量分布与实验数据进行了比较，显示出良好的一致性。分析了初级和总LET分布，以研究不同深度区域中次级粒子贡献的影响。一个不可忽略的影响，高LET组件被发现在入口通道的质子束，确定总剂量平均LET的因子3高于主要的。对于碳离子，情况完全不同。在这种情况下，二次粒子主要贡献于峰后的尾部。结果表明，轻和重的二次离子的重量可以显着影响的LET深度分布的计算。这在解释来自放射生物学实验的结果中具有重要作用，因此，在强子治疗计划程序中具有重要作用。
Fluence, depth absorbed dose and linear energy transfer (LET) distributions of proton and carbon ion beams have been investigated using the Monte Carlo code Geant4 (GEometry ANd Tracking). An open source application was developed with the aim to simulate two typical transport beam lines, one used for ocular therapy and cell irradiations with protons and the other for cell irradiations with carbon ions. This tool allows evaluation of the primary and total dose averaged LET and predict their spatial distribution in voxelized or sliced geometries. In order to reproduce the LET distributions in a realistic way, and also the secondary particles' contributions due to nuclear interactions were considered in the computations. Pristine and spread-out Bragg peaks were taken into account both for proton and carbon ion beams, with the maximum energy of 62 MeV/n. Depth dose distributions were compared with experimental data, showing good agreement. Primary and total LET distributions were analysed in order to study the influence of contributions of secondary particles in regions at different depths. A non-negligible influence of high-LET components was found in the entrance channel for proton beams, determining the total dose averaged LET by the factor 3 higher than the primary one. A completely different situation was obtained for carbon ions. In this case, secondary particles mainly contributed in the tail that is after the peak. The results showed how the weight of light and heavy secondary ions can considerably influence the computation of LET depth distributions. This has an important role in the interpretation of results coming from radiobiological experiments and, therefore, in hadron treatment planning procedures.