Dosimetric verification of IMPT using a commercial heterogeneous phantom.
Dosimetric verification of IMPT using a commercial heterogeneous phantom.
复制标题
使用商业异质模型对 IMPT 进行剂量验证。
DOI：
10.1002/acm2.12535
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Ogino H.
中科院分区：
文献类型：
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作者：
Yasui K;Toshito T;Omachi C;Hayashi K;Kinou H;Katsurada M;Hayashi N;Ogino H.
本研究的目的是使用市售异质体模提出强度调制质子治疗（IMPT）的验证方法和结果。我们使用了一个简单的模拟头颈部和前列腺体模。用电离室和辐射变色胶片测量绝对剂量和相对剂量分布。使用治疗计划系统将测量的剂量与计算的剂量进行比较。我们定义电离室测量点的不确定度，由于室的有效点和机械设置误差为2 mm，估计剂量变化的基础上，2 mm的误差。我们准备了特定于异质体模的HU相对阻止本领转换表和通量校正因子。通量校正因子被确定为深度的函数，并从相同有效深度的水中和体模中的剂量比获得。在模拟前列腺计划中，测量和计算的复合剂量在±1.3%内一致，每个射野的最大局部剂量差异为10.0%。模拟头颈部计划中的复合剂量在4.0%范围内一致，每个射野的最大局部剂量差异为12.0%。在考虑测量不确定度的情况下，每个射野的剂量差异在2%以内。在复合计划中，模拟前列腺计划的最大剂量不确定性估计为4.0%，模拟头颈部计划的最大剂量不确定性估计为5.8%。胶片测量显示出良好的一致性，超过92.5%的点通过伽马值（3%/3 mm）。根据这些结果，通过使用体模特定HU相对阻止本领转换、通量校正因子和由于腔室有效点引起的剂量误差估计，异质体模应可用于验证IMPT。
The purpose of this study was to propose a verification method and results of intensity‐modulated proton therapy (IMPT), using a commercially available heterogeneous phantom. We used a simple simulated head and neck and prostate phantom. An ionization chamber and radiochromic film were used for measurements of absolute dose and relative dose distribution. The measured doses were compared with calculated doses using a treatment planning system. We defined the uncertainty of the measurement point of the ionization chamber due to the effective point of the chamber and mechanical setup error as 2 mm and estimated the dose variation base on a 2 mm error. We prepared a HU‐relative stopping power conversion table and fluence correction factor that were specific to the heterogeneous phantom. The fluence correction factor was determined as a function of depth and was obtained from the ratio of the doses in water and in the phantom at the same effective depths. In the simulated prostate plan, composite doses of measurements and calculations agreed within ±1.3% and the maximum local dose differences of each field were 10.0%. Composite doses in the simulated head and neck plan agreed within 4.0% and the maximum local dose difference for each field was 12.0%. The dose difference for each field came within 2% when taking the measurement uncertainty into consideration. In the composite plan, the maximum dose uncertainty was estimated as 4.0% in the simulated prostate plan and 5.8% in the simulated head and neck plan. Film measurements showed good agreement, with more than 92.5% of points passing a gamma value (3%/3 mm). From these results, the heterogeneous phantom should be useful for verification of IMPT by using a phantom‐specific HU‐relative stopping power conversion, fluence correction factor, and dose error estimation due to the effective point of the chamber.