Spatial fractionation of the dose in heavy ions therapy: An optimization study
Spatial fractionation of the dose in heavy ions therapy: An optimization study
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DOI：
10.1002/mp.12902
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发表时间：
2018-06-01
期刊：
影响因子：
3.8
通讯作者：
Prezadoa, Y.
中科院分区：
文献类型：
--
作者：
Gonzalez, W.;Prezadoa, Y.
目的：带电粒子治疗和剂量空间分割的结合，如微型束或网格治疗，是提高放射抗性肿瘤治疗中治疗指数的创新策略。这项工作的目的是从离子种类、束宽、中心到中心距离和线性能量转移 (LET) 方面评估重离子空间分割放射治疗 (SFRT) 的最佳照射配置，这些信息可用于指导未来生物实验的设计。核碎裂导致峰区和谷区由不同的次级粒子组成，因此需要比 SFRT 中的经典剂量学描述更完整的剂量学描述。方法：进行蒙特卡罗模拟 (GATE 6.2)，以评估不同离子、束宽和间距的剂量分布。我们还评估了平均剂量 LET 的 3D 图，并提出了一个新参数，即峰谷 LET 比，以对该技术进行更彻底的物理评估。结果：我们的结果表明，需要大于 400 μm 的束宽，以保持入口剂量与目标剂量之间的比例与传统照射相同。大的 ctc 距离（3500 μ m）将有利于组织保护，因为它提供了更高的 PVDR，它导致较重的核碎片的贡献减少，并且谷中的 LET 值比 ctc 中的 LET 低 2 倍，从而导致目标中的均匀分布。结论：重离子 MBRT 提供有利的剂量分布。由于横向散射减少，使用亚毫米光束仍然可以保持入口剂量与目标剂量之间的比例与传统照射相同。应优先选择大的 CTC 距离（3500 μm），因为它们会导致由较轻的核碎片组成的谷剂量，从而导致正常组织中的剂量平均 LET 值大大降低，有利于其保存。在评估的不同离子种类中，Ne 是一种能够在正常组织中的高 PVDR 和 PVLR 与高 LET 值（接近 100 keV/μm）以及目标区域中有利的氧增强比之间实现最佳平衡的离子。 (c) 2018年美国医学物理学家协会
Purpose: The alliance of charged particle therapy and the spatial fractionation of the dose, as in minibeam or Grid therapy, is an innovative strategy to improve the therapeutic index in the treatment of radioresistant tumors. The aim of this work was to assess the optimum irradiation configuration in heavy ion spatially fractionated radiotherapy (SFRT) in terms of ion species, beam width, center-tocenter distances, and linear energy transfer (LET), information that could be used to guide the design of the future biological experiments. The nuclear fragmentation leading to peak and valley regions composed of different secondary particles, creates the need for a more complete dosimetric description that the classical one in SFRT.Methods: Monte Carlo simulations (GATE 6.2) were performed to evaluate the dose distributions for different ions, beam widths, and spacings. We have also assessed the 3D-maps of dose-averaged LET and proposed a new parameter, the peak-to-valley-LET ratio, to offer a more thorough physical evaluation of the technique.Results: Our results show that beam widths larger than 400 mu m are needed in order to keep a ratio between the dose in the entrance and the dose in the target of the same order as in conventional irradiations. A large ctc distance (3500 mu m) would favor tissue sparing since it provides higher PVDR, it leads to a reduced contribution of the heavier nuclear fragments and a LET value in the valleys a factor 2 lower than the LET in the ctc leading to homogeneous distributions in the target.Conclusions: Heavy ions MBRT provide advantageous dose distributions. Thanks to the reduced lateral scattering, the use of submillimetric beams still allows to keep a ratio between the dose in the entrance and the dose in the target of the same order as in conventional irradiations. Large ctc distances (3500 mu m) should be preferred since they lead to valley doses composed of lighter nuclear fragments resulting in a much reduced dose-averaged LET values in normal tissue, favoring its preservation. Among the different ions species evaluated, Ne stands out as the one leading to the best balance between high PVDR and PVLR in normal tissues and high LET values (close to 100 keV/mu m) and a favorable oxygen enhancement ratio in the target region. (c) 2018 American Association of Physicists in Medicine