Linear energy transfer incorporated intensity modulated proton therapy optimization.
Linear energy transfer incorporated intensity modulated proton therapy optimization.
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DOI：
10.1088/1361-6560/aa9a2e
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发表时间：
2017-12-19
影响因子：
3.5
通讯作者：
Mohan R
中科院分区：
文献类型：
--
作者：
Cao W;Khabazian A;Yepes PP;Lim G;Poenisch F;Grosshans DR;Mohan R
本研究的目的是探讨将线性能量转移（LET）纳入强度调制质子治疗（IMPT）计划优化的可行性。由于LET增加与质子的生物有效性增加相关，因此在IMPT计划中，靶体积的高LET和关键结构和正常组织的低LET是首选。然而，如果没有明确纳入优化准则，不同的IMPT计划可能产生相似的物理剂量分布，但LET分布却有很大不同，特别是剂量平均LET分布。通常，IMPT优化准则（或成本函数）只包括基于剂量的目标，其中假定相对生物有效性（RBE）具有恒定值1.1。在这项研究中，我们增加了基于LET的目标，以最大化靶体积中的LET，并最小化关键结构和正常组织中的LET。由于结果模型的分数规划性质，我们使用了变量重新表述方法，以便优化过程在计算上等同于传统的IMPT优化。本研究选取5名在本院接受质子治疗的脑肿瘤患者。针对每位患者创建了两种方案，一种是拟议的let合并优化方案（LETOpt），另一种是传统的基于剂量的优化方案（DoseOpt）。在剂量（假设临床实践中采用恒定的RBE为1.1）和LET方面比较优化方案。两种优化方法都能产生相似的剂量分布。与传统的基于剂量的优化相比，纳入LET的优化不仅显著降低了脑干和视交叉等关键器官的LET值，而且增加了靶体积的LET。然而，有时需要权衡剂量和LET分布的可接受性。我们的结论是，在IMPT优化中纳入LET依赖标准可以导致与传统优化相似的剂量分布，但靶体积和正常组织中的LET分布更优。这可能在改善肿瘤控制和减少正常组织毒性方面具有实质性的优势。
The purpose of this study was to investigate the feasibility of incorporating linear energy transfer (LET) into the optimization of intensity modulated proton therapy (IMPT) plans. Because increased LET correlates with increased biological effectiveness of protons, high LETs in target volumes and low LETs in critical structures and normal tissues are preferred in an IMPT plan. However, if not explicitly incorporated into the optimization criteria, different IMPT plans may yield similar physical dose distributions but greatly different LET, specifically dose-averaged LET, distributions. Conventionally, the IMPT optimization criteria (or cost function) only includes dose-based objectives in which the relative biological effectiveness (RBE) is assumed to have a constant value of 1.1. In this study, we added LET-based objectives for maximizing LET in target volumes and minimizing LET in critical structures and normal tissues. Due to the fractional programming nature of the resulting model, we used a variable reformulation approach so that the optimization process is computationally equivalent to conventional IMPT optimization. In this study, five brain tumor patients who had been treated with proton therapy at our institution were selected. Two plans were created for each patient based on the proposed LET-incorporated optimization (LETOpt) and the conventional dose-based optimization (DoseOpt). The optimized plans were compared in terms of both dose (assuming a constant RBE of 1.1 as adopted in clinical practice) and LET. Both optimization approaches were able to generate comparable dose distributions. The LET-incorporated optimization achieved not only pronounced reduction of LET values in critical organs, such as brainstem and optic chiasm, but also increased LET in target volumes, compared to the conventional dose-based optimization. However, on occasion, there was a need to tradeoff the acceptability of dose and LET distributions. Our conclusion is that the inclusion of LET-dependent criteria in the IMPT optimization could lead to similar dose distributions as the conventional optimization but superior LET distributions in target volumes and normal tissues. This may have substantial advantage in improving tumor control and reducing normal tissue toxicities.
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DOI：
10.1016/j.ijrobp.2016.08.038
发表时间：
2016-12-01
影响因子：
7
作者：
Unkelbach, Jan;Botas, Pablo;Paganetti, Harald
通讯作者：
Paganetti, Harald
影响因子：
3.5
作者：
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通讯作者：
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影响因子：
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影响因子：
3.5
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通讯作者：
Paganetti, H.
影响因子：
3.5
作者：
Chan, TCY;Bortfeld, T;Tsitsiklis, JN
通讯作者：
Tsitsiklis, JN