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Research for high-accuracy dose calculation methods for proton treatment planning

质子治疗计划高精度剂量计算方法研究

基本信息

批准号：
12670851
负责人：
TAKADA Yoshihisa
金额：
$ 2.18万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12670851/
关键词：
treatment planning proton beam pencil beam method broad beam method Monte Carlo method Modulated Pencil Beam Algorithm open beam incident beam model Modulated Pencil Beam Algorithng 陽子線治療有効線源モデル 2重散乱体ペンシルビーム

项目摘要

Dose-calculation methods for proton treatment planning has been improved to obtain more accurate dose prediction. We used phantoms to verify the accuracies. Pencil beam methods were found to be more effective than the broad beam method. An incident beam model has been improved to obtain more accurate dose prediction. We developed a Range-Modulated Pencil Beam Method (RMPBA) to reduce the calculation time by an order of magnitude yet keeping the accuracy. We verified that the pencil beam algorithms are effective to reproduce measured dose distributions in water of protons traversing the material including a range compensator (=bolus). In contrast, noticeable discrepancies between measurements and calculations made by the pencil beam method were found in media with large lateral heterogeneities. The reason for the discrepancies is due to the incorrect scattering model of the pencil beam method. Monte Carlo calculations are effective to improve the situation. However, full Monet Carlo calculations using GEANT3 or LAHET, etc, are time-consuming. We applied a simplified Monte Carlo (SMC) method to improve the calculation accuracy of dose distributions. It is found that reduction of calculation time is possible by the SMC method and parallel processing using several CPUs will enable dose calculation for realistic targets within thirty minutes. In conclusion, it is practical to use the pencil beam algorithm for dose calculations for targets with moderate lateral heterogeneities along the beam paths. For targets with large lateral heterogeneities along the beam paths, Monte Carlo calculations are strongly recommended.

质子治疗计划的剂量计算方法已得到改进，以获得更准确的剂量预测。我们用幻影来验证准确性。铅笔梁法比宽梁法更有效。对入射光束模型进行了改进，以获得更准确的剂量预测。提出了一种距离调制铅笔束法（RMPBA），在保持精度的前提下，将计算时间缩短了一个数量级。我们验证了铅笔束算法可以有效地再现水中质子穿过材料的测量剂量分布，包括范围补偿器（=bolus）。相比之下，在横向非均质性较大的介质中，铅笔束法的测量结果和计算结果之间存在明显差异。造成这种差异的原因是由于铅笔束法的散射模型不正确。蒙特卡罗计算有效地改善了这种情况。但是，使用GEANT3或LAHET等进行完整的莫奈卡罗计算非常耗时。为了提高剂量分布的计算精度，我们采用了一种简化的蒙特卡罗（SMC）方法。采用SMC方法可以缩短计算时间，使用多个cpu并行处理可以在30分钟内计算出实际目标的剂量。总之，对于沿光束路径具有中等横向非均匀性的目标，使用铅笔束算法进行剂量计算是可行的。对于沿光束路径具有较大横向非均匀性的目标，强烈建议使用蒙特卡罗计算。