Reoptimization of Intensity Modulated Proton Therapy Plans Based on Linear Energy Transfer
Reoptimization of Intensity Modulated Proton Therapy Plans Based on Linear Energy Transfer
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DOI：
10.1016/j.ijrobp.2016.08.038
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发表时间：
2016-12-01
影响因子：
7
通讯作者：
Paganetti, Harald
中科院分区：
文献类型：
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作者：
Unkelbach, Jan;Botas, Pablo;Paganetti, Harald
目的：我们描述了一种用于强度调制质子治疗（IMPT）的治疗计划优化方法，该方法避免了位于靶体积内或附近的关键结构中的高线性能量传递（LET）值，同时限制了最佳可能物理剂量分布的退化。为了允许基于剂量和LET的快速优化，扩展了基于GPU的Monte Carlo代码，以提供除所有笔形射束的剂量之外的剂量平均LET。在基于物理剂量优化初始IMPT计划之后，使用优先优化方案来修改LET分布，同时将物理剂量目标约束为接近初始计划的值。LET优化步骤是基于针对LET和物理剂量（LET x D）的乘积评估的目标函数执行的。第一近似，LET × D表示的额外的生物剂量，是由高LET.Results：该方法是有效的治疗序列的关键结构与最大剂量的限制位于目标内或附近。我们报告了5例颅内肿瘤（高级别脑膜瘤、颅底脊索瘤、室管膜瘤），其靶体积与脑干和视神经结构重叠。在所有情况下，高LET x D在关键结构中可以避免，同时最小限度地损害物理剂量规划objectives.Conclusion：LET为基础的IMPT计划的再优化是一个务实的方法来弥合纯粹的物理剂量为基础的和相对生物学效应（RBE）为基础的规划之间的差距差距。该方法通过减轻由接近范围末端的质子束的RBE升高引起的副作用的潜在增加的风险，使IMPT治疗更安全。(C)2016 Elsevier Inc. All rights reserved.
Purpose: We describe a treatment plan optimization method for intensity modulated proton therapy (IMPT) that avoids high values of linear energy transfer (LET) in critical structures located within or near the target volume while limiting degradation of the best possible physical dose distribution.Methods and Materials: To allow fast optimization based on dose and LET, a GPU-based Monte Carlo code was extended to provide dose-averaged LET in addition to dose for all pencil beams. After optimizing an initial IMPT plan based on physical dose, a prioritized optimization scheme is used to modify the LET distribution while constraining the physical dose objectives to values close to the initial plan. The LET optimization step is performed based on objective functions evaluated for the product of LET and physical dose (LET x D). To first approximation, LET x D represents a measure of the additional biological dose that is caused by high LET.Results: The method is effective for treatments where serial critical structures with maximum dose constraints are located within or near the target. We report on 5 patients with intracranial tumors (high-grade meningiomas, base-of-skull chordomas, ependymomas) in whom the target volume overlaps with the brainstem and optic structures. In all cases, high LET x D in critical structures could be avoided while minimally compromising physical dose planning objectives.Conclusion: LET-based reoptimization of IMPT plans represents a pragmatic approach to bridge the gap between purely physical dose-based and relative biological effectiveness (RBE)-based planning. The method makes IMPT treatments safer by mitigating a potentially increased risk of side effects resulting from elevated RBE of proton beams near the end of range. (C) 2016 Elsevier Inc. All rights reserved.