Efficacy of robust optimization plan with partial-arc VMAT for photon volumetric-modulated arc therapy: A phantom study.
Efficacy of robust optimization plan with partial-arc VMAT for photon volumetric-modulated arc therapy: A phantom study.
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DOI：
10.1002/acm2.12131
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发表时间：
2017-09
影响因子：
2.1
通讯作者：
Nagata Y
中科院分区：
文献类型：
--
作者：
Miura H;Ozawa S;Nagata Y
本研究调查了使用全弧和部分弧体积调制弧治疗（VMAT）的基于计划靶体积（PTV）和稳健优化计划中的位置依赖性。外围、中间和中心CTV位置的机架角度为181°-180°（全弧VMAT）和181°-360°（部分弧VMAT）。基于PTV的优化计划通过将CTV边缘扩展5 mm至PTV体积来定义，并对其应用剂量约束。稳健优化计划包括在最大不确定度设置为5 mm的条件下直接优化CTV剂量。处方剂量标准化为CTV D99%（覆盖CTV体积99%的最小相对剂量）作为原始计划。在前-后（A-P）、上级-下（S-I）和右-左（R-L）方向上，等中心点以1 mm的间隔从原始位置刚性移动到原始计划中的最大不确定度设置5 mm，产生重新计算的剂量分布。结果发现，对于中间和中心位置，当比较基于PTV的优化计划和稳健优化计划时，所有方向CTV的D99%剂量的不确定性没有显著差异（P > 0.05）。对于外周位置，稳健优化计划的R-L方向CTV的D99%剂量的不确定性低于基于PTV的优化计划（P < 0.05）。我们的研究表明，使用部分弧VMAT的稳健优化计划的有效性取决于外周CTV位置。
This study investigated position dependence in planning target volume (PTV)‐based and robust optimization plans using full‐arc and partial‐arc volumetric modulated arc therapy (VMAT). The gantry angles at the periphery, intermediate, and center CTV positions were 181°–180° (full‐arc VMAT) and 181°–360° (partial‐arc VMAT). A PTV‐based optimization plan was defined by 5 mm margin expansion of the CTV to a PTV volume, on which the dose constraints were applied. The robust optimization plan consisted of a directly optimized dose to the CTV under a maximum‐uncertainties setup of 5 mm. The prescription dose was normalized to the CTV D99% (the minimum relative dose that covers 99% of the volume of the CTV) as an original plan. The isocenter was rigidly shifted at 1 mm intervals in the anterior‐posterior (A‐P), superior‐inferior (S‐I), and right‐left (R‐L) directions from the original position to the maximum‐uncertainties setup of 5 mm in the original plan, yielding recalculated dose distributions. It was found that for the intermediate and center positions, the uncertainties in the D99% doses to the CTV for all directions did not significantly differ when comparing the PTV‐based and robust optimization plans (P > 0.05). For the periphery position, uncertainties in the D99% doses to the CTV in the R‐L direction for the robust optimization plan were found to be lower than those in the PTV‐based optimization plan (P < 0.05). Our study demonstrated that a robust optimization plan's efficacy using partial‐arc VMAT depends on the periphery CTV position.
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