基于简化机头模型与筒串卷积算法的调强计划独立三维剂量验算

目的 建立医用直线加速器的双点源机头模型,结合筒串卷积算法实现调强治疗计划三维独立剂量验算。 方法 分别对瓦里安、医科达直线加速器建立双点源机头模型,结合筒串卷积剂量算法计算三维剂量分布。与电离室水箱扫描数据比较规则野的Scp、PDD、离轴剂量分布确认计算模型。两种加速器分别各选取 12例共 24例调强治疗计划进行比较,对TPS计算结果进行独立验算,并且与探测器矩阵测量结果进行比较。 结果 矩形野中心点剂量偏差均<1%,射野内相同位置二者剂量偏差≤1%,半影区域位置偏差≤1 mm。采用3%/3 mm标准γ通过率均>90%。 结论 建立了基于双点源机头模型结合筒串卷积算法实现调强治疗计划三维独立剂量验算,对规则射野及调强治疗计划的验证比较,表明该方法和计算模型可用于临床计划的三维独立剂量验算。

Independent 3D dose calculation for IMRT based on simplification of beam model and collapsed-cone convolution/superposition algorithm

Objective To realize independent 3D dose calculation for intensity-modulated radiotherapy (IMRT) by building a two-source beam model of medical linear accelerator combined with a collapsed-cone convolution/superposition (CCCS) algorithm.Methods Two-source beam models of medical linear accelerators (Varian and Elekta) were built to calculate the 3D dose distributions using the CCCS algorithm.Scp,percent depth dose,and off-axis dose distribution were compared with the scanning data of ion chamber to confirm the calculation model.Twelve intensity-modulated treatment plans from each accelerator (a total of 24 plans) were selected for comparison.The calculation results of treatment planning system (TPS) were independently validated,and further compared with the measurement results of detector matrix.Results The dose deviations at the center of rectangle fields were lower than 1%,the deviation between doses at the same position in the field was not higher than 1%,and the positional deviation in the penumbra region was not higher than 1 mm.Gamma analysis based on 3%/3 mm standard was used to compare the results calculated by detectors and TPS.The pass rates were higher than 90%.Conclusions The independent 3D dose calculation for IMRT based on two-source beam model combined with CCCS algorithm has been successfully set up.The comparison between regular field and IMRT plan indicates that this method and calculation model can be used for independent 3D dose calculation of clinical plan.