MONTE CARLO SIMULATIONS OF SPATIAL LET DISTRIBUTIONS IN CLINICAL PROTON BEAMS
MONTE CARLO SIMULATIONS OF SPATIAL LET DISTRIBUTIONS IN CLINICAL PROTON BEAMS
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DOI：
10.1093/rpd/ncx272
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发表时间：
2018-08-01
影响因子：
1
通讯作者：
Bassler, Niels
中科院分区：
文献类型：
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作者：
Grzanka, Leszek;Ardenfors, Oscar;Bassler, Niels
线性能量传递（LET）通常用作描述快离子放射治疗中所应用辐射质量的一个参数。特别是在质子治疗中，大多数预测所应用射束放射生物学特性的模型都与剂量平均LET（LETd）相适配。相关的注量平均或径迹平均LET（LETt）这一参数使用频率较低。LETt尤其是LETd都在很大程度上取决于所遇到的次级粒子谱。对于包含所有次级粒子的质子束，在质子场的入射通道中LETd可能达到3 keV/μm以上。然而，通常带电粒子谱仅在初级和次级质子上取平均，对于同一区域约为0.5 keV/μm。这等同于假设来自较重离子的次级粒子谱对所产生的放射生物学无关，这是一个需要更深入研究的论断。依赖于LETd的模型也应该明确所使用的LETd类型，但情况并非总是如此。在这项工作中，我们扩展了蒙特卡罗粒子输运代码SHIELD - HIT12A，以便为离子放射治疗计划提供剂量平均和径迹平均的LET图。
The linear energy transfer (LET) is commonly used as a parameter which describes the quality of the radiation applied in radiation therapy with fast ions. In particular in proton therapy, most models which predict the radiobiological properties of the applied beam, are fitted to the dose-averaged LET, LETd. The related parameter called the fluence-or track-averaged LET, LETt, is less frequently used. Both LETt and in particular LETd depends profoundly on the encountered secondary particle spectrum. For proton beams including all secondary particles, LETd may reach more than 3 keV/um in the entry channel of the proton field. However, typically the charged particle spectrum is only averaged over the primary and secondary protons, which is in the order of 0.5 keV/um for the same region. This is equal to assuming that the secondary particle spectrum from heavier ions is irrelevant for the resulting radiobiology, which is an assertion in the need of closer investigation. Models which rely on LETd should also be clear on what type of LETd is used, which is not always the case. Within this work, we have extended the Monte Carlo particle transport code SHIELD-HIT12A to provide dose-and track-average LET-maps for ion radiation therapy treatment plans.