Experimental characterization of lateral profiles of scanned proton and carbon ion pencil beams for improved beam models in ion therapy treatment planning
Experimental characterization of lateral profiles of scanned proton and carbon ion pencil beams for improved beam models in ion therapy treatment planning
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DOI：
10.1088/0031-9155/56/24/009
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发表时间：
2011-12-21
影响因子：
3.5
通讯作者：
Parodi, K.
中科院分区：
文献类型：
--
作者：
Schwaab, J.;Brons, S.;Parodi, K.
扫描离子笔束带有一个低剂量包络线，该包络线可以从单个离子束中心轴延伸至几厘米。根据光束的能量和种类，该光晕主要由目标中的核相互作用产生的二次粒子或在光束线分量中经历多次库仑散射的粒子组成。当前治疗计划系统中的单高斯光束建模经常忽略这种光环。提高治疗计划准确性的一种可能性是通过添加低剂量包络线的描述来升级所使用的笔形射束模型。但与此同时，将治疗计划的计算时间和复杂性保持在合理的范围内也至关重要。作为第一种方法，我们在海德堡离子束治疗中心测量了水和空气中不同能量和深度的扫描质子和碳离子笔形束的横向束剖面。然后，我们尝试通过向我们的治疗计划系统目前使用的标准单高斯模型添加补充高斯函数来描述它们的光束光晕。该分析有助于确定描述横向光束展宽的参数趋势，以支持其建模。最后，结果表明，通过所提出的笔形射束模型升级可以提高治疗计划的准确性。特别是，所提出的实验数据可以直接用作剂量计算的输入，也可以用于与计算模型的结果进行代表性比较，例如蒙特卡罗模拟，用于生成要输入到治疗计划系统的升级射束模型中的横向基本数据。
Scanned ion pencil beams carry a low-dose envelope which can extend up to several centimeters from the individual beam central axis. Depending on the energy and species of the beam, this halo consists mainly of secondary particles produced by nuclear interactions in the target or of particles undergoing multiple Coulomb scattering in the beam line components. This halo is often neglected by single Gaussian beam modeling in current treatment planning systems. One possibility of improving the accuracy of treatment planning is to upgrade the used pencil beam models by adding a description of the low-dose envelope. But at the same time it is crucial to keep the calculation time and the complexity for treatment planning in reasonable limits. As a first approach we measured the lateral beam profiles of scanned proton and carbon ion pencil beams at different energies and depths in water and air at the Heidelberg Ion Beam Therapy Center. Then we tried to describe their beam halo by adding a supplementary Gaussian function to the standard single Gauss modeling which is used at the moment by our treatment planning systems. This analysis helped to identify trends in the parameters describing the lateral beam broadening to support its modeling. Finally, it is shown that the accuracy of treatment planning could be improved by the proposed upgrade of the pencil beam model. In particular, the presented experimental data can be either used directly as input for dose calculation or serve for representative comparison with the results of calculation models such as Monte Carlo simulations for the generation of lateral basic data to be input in upgraded beam models of treatment planning systems.