Simultaneous dose and dose rate optimization (SDDRO) for FLASH proton therapy
Simultaneous dose and dose rate optimization (SDDRO) for FLASH proton therapy
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DOI：
10.1002/mp.14531
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发表时间：
2020-11-08
期刊：
影响因子：
3.8
通讯作者：
Bradley, Jeffery
中科院分区：
文献类型：
--
作者：
Gao, Hao;Lin, Bowen;Bradley, Jeffery
目的：闪光放射疗法（RT）可以潜在地降低正常的组织毒性，同时保留肿瘤的有效性以提高治疗比率。用于保留正常组织的闪光灯的关键是用超高剂量速率（即> = 40 gy/s）照射组织，可以使用质子RT。但是，当前可用的治疗计划优化方法仅优化剂量分布，并且不会直接优化剂量率。这项工作对闪光质子RT的贡献是一种新型治疗优化方法的开发，即同时剂量和剂量率优化（SDDRO），以优化组织引起的剂量率分布和剂量分布。现有方法，SDDRO考虑剂量率约束并优化剂量率分布。在数学配方方面，SDDRO是剂量分布的剂量限制，对剂量平均组织剂量剂量速率的最低剂量率约束，最小剂量率的限制，最小监测剂对点重量的最小监测单位约束以及对光束强度的最大强度约束对剂量率的最低限制，对光束强度的最小监测剂限制，对光束强度的最小限制，对剂量率的最低限制，以及。在优化算法方面，通过迭代凸松弛和乘数交替方向方法来解决SDDRO。将SDDRO算法用于恒定或可变光束强度的两种情况。分子：SDDRO与强度调制的质子治疗（IMPT）（单独优化剂量优化，无剂量率优化），使用三个肺病例进行了比较。与IMPT相比，SDDRO显着提高了剂量速率分布，例如，增加利益区域（ROI）体积（ROI = CTV_10MM：由10 mm外部和CTV边界的内部扩张夹住的环）至少收到40 Gy /s从相似至30-50％至至少98％，肺部量至少40 Gy/s从相似到30-40％到类似70-90％。此外，SDDRO的剂量和剂量率分布均通过次级使用和多种光束进一步改善。结论：我们已经开发了一种闪光灯质子RT的关节剂量和剂量速率优化方法，即SDDRO，即首先是SDDRO - 据我们所知。结果表明，与IMPT相比，（例如，就剂量率量直方图而言），SDDRO可以实质上改善闪光剂量的覆盖率（例如，就剂量率量直方图而言），同时保留了剂量分布，并且（b）组合的组合是正常组织的差异。高剥离和多个光束可以从剂量和剂量率分布方面进一步改善SDDRO计划质量。 （c）2020美国医学物理学家协会[https://doi.org/10.1002/mp.14531]
Purpose: FLASH radiotherapy (RT) can potentially reduce normal tissue toxicity while preserving tumoricidal effectiveness to improve the therapeutic ratio. The key of FLASH for sparing normal tissues is to irradiate tissues with an ultra-high dose rate (i.e., >= 40 Gy/s), for which proton RT can be used. However, currently available treatment plan optimization method only optimizes the dose distribution and does not directly optimize the dose rate. The contribution of this work to FLASH proton RT is the development of a novel treatment optimization method, that is, simultaneous dose and dose rate optimization (SDDRO), to optimize tissue-receiving dose rate distribution as well as dose distribution.Methods: Distinguished from existing methods, SDDRO accounts for dose rate constraint and optimizes dose rate distribution. In terms of mathematical formulation, SDDRO is a constrained optimization problem with dose-volume constraint on dose distribution, minimum dose rate constraint on dose-averaged tissue-receiving dose rates, minimum monitor unit constraint on spot weight, and maximum intensity constraint on beam intensity. In terms of optimization algorithm, SDDRO is solved by iterative convex relaxation and alternating direction method of multipliers. SDDRO algorithms are presented for both scenarios with either constant or variable beam intensity.Results: SDDRO was compared with intensity modulated proton therapy (IMPT) (dose optimization alone, and no dose rate optimization) using three lung cases. SDDRO substantially improved the dose rate distribution compared to IMPT, for example, increasing of the region-of-interest (ROI) volume (ROI = CTV_10mm: the ring sandwiched by 10 mm outer and inner expansion of CTV boundary) receiving at least 40 Gy/s from similar to 30-50% to at least 98%, and the lung volume receiving at least 40 Gy/s from similar to 30-40% to similar to 70-90%. Moreover, both dose and dose rate distributions from SDDRO were further considerably improved via the combined use of hypofractionation and multiple beams.Conclusions: We have developed a joint dose and dose rate optimization method for FLASH proton RT, namely SDDRO, which is first-of-its-kind to the best of our knowledge. The results suggest that (a) SDDRO can substantially improve the FLASH-dose rate coverage (e.g., in terms of dose rate volume histogram) compared to IMPT for the purpose of normal tissue sparing while preserving the dose distribution and (b) the combination of hypofractionation and multiple beams can further considerably improve the SDDRO plan quality in terms of both dose and dose rate distribution. (c) 2020 American Association of Physicists in Medicine [https://doi.org/10.1002/mp.14531]