The impact of electron transport on the accuracy of computed dose
The impact of electron transport on the accuracy of computed dose
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DOI：
10.1118/1.599004
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发表时间：
2000-06-01
期刊：
影响因子：
3.8
通讯作者：
Mohan, R
中科院分区：
文献类型：
--
作者：
Arnfield, MR;Siantar, CH;Mohan, R
这项工作的目的是研究由巴斯幂定律修正和两种考虑电子射程的模型预测剂量的准确性：叠加/卷积算法和蒙特卡罗算法。将这些模型的结果在具有空洞和低密度不均匀的体模中进行了比较。考虑了一种理想化的几何形状，用空气和肺等效物质的区域来表示不均匀。使用平行板电离室、薄层热释光剂量计和胶片进行测量。剂量计算采用广义Bathe模型、尖顶折叠圆锥卷积模型(CCC)和游程蒙特卡罗剂量计算算法。比较了不同深度相对于非均匀界面的绝对中心轴和离轴剂量数据。我们的结果证实，对于洗澡校正，计算的深度剂量中的剂量误差是由于忽略了电子输运引起的。这种效应随场大小的减小、不均匀密度的减小以及入射光子的能量的增大而增大。CCC的计算比BASH模型更接近实测值，但仍存在显著差异。蒙特卡罗结果在测量和计算不确定度范围内与测量结果一致。(C)2000年美国医学物理学家协会。[S0093-2405(00)00906-8]。
The aim of this work was to investigate the accuracy of dose predicted by a Bathe power law correction, and two models which account for electron range: A superposition/convolution algorithm and a Monte Carlo algorithm. The results of these models were compared in phantoms with cavities and low-density inhomogeneities. An idealized geometry was considered with inhomogeneities represented by regions of air and lung equivalent material. Measurements were performed with a parallel plate ionization chamber, thin TLDs (thermoluminescent dosimeters) and film. Dose calculations were done with a generalized Bathe model, the Pinnacle collapsed cone convolution model (CCC), and the Peregrine Monte Carlo dose calculation algorithm. Absolute central axis and off axis dose data at various depths relative to interfaces of inhomogeneities were compared. Our results confirm that for a Bathe correction, dose errors in the calculated depth dose arise from the neglect of electron transport. This effect increases as the field size decreases, as the density of the inhomogeneity decreases, and with the energy of incident photons. The CCC calculations were closer to measurements than the Bathe model, but significant discrepancies remain. Monte Carlo results agree with measurements within the measurement and computational uncertainties. (C) 2000 American Association of Physicists in Medicine. [S0093-2405(00)00906-8].