Experimental and Monte Carlo evaluation of Eclipse treatment planning system for lung dose calculations
Experimental and Monte Carlo evaluation of Eclipse treatment planning system for lung dose calculations
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DOI：
10.1016/s1507-1367(06)71057-4
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发表时间：
2006-01-01
影响因子：
1.2
通讯作者：
Reilly, Andrew J.
中科院分区：
文献类型：
--
作者：
Mesbahi, Asghar;Thwaites, David I.;Reilly, Andrew J.
背景在这项研究中的笔形射束为基础的治疗计划系统（TPS）的准确性进行了评估肺剂量计算的比较与测量和蒙特卡罗（MC）method.Aim在目前的研究中，我们评估的Eclipse治疗计划系统在胸部区域的电离室测量和蒙特卡罗计算的性能。本文研究了两种胸部辐照度的分析方法：改进的组织空气比（MB）法和等效组织空气比（ETAR）法。对于胸部体模中的蒙特卡罗计算，我们对Varian Clinac 2100 EX直线加速器进行了建模。在对我们的模型与水模测量进行基准测试后，我们使用该模型进行胸部模calculation.Materials/Methods 8和15 MV光子束的Varian 21 EX直线加速器用于辐照。利用MANP 4C蒙特卡罗程序对直线加速器头部的几何形状进行了模拟。在调试“MC”束流模型后，用蒙特卡罗（MC）方法计算肺剂量。辐照病例为：（1）单肺后野，野径为4 × 4和10 × 10 cm（2）;（2）胸部侧野，野径为4 × 4和10 × 10 cm（2）。对于4x 4cm（2）的射野大小，TPS计算和测量之间的局部剂量最大差异为+33%（MB）和+28%（ETAR）。此外，他们忽略了由于小射野尺寸的横向电子平衡导致的肺剂量降低。对于实施这些算法的其他TPS，预期会有类似的结果。MC计算与测量结果非常一致，显示所有测量点的局部差异不超过2%。结论我们的研究结果显示，肺内4x 4cm（2）射野大小点的分析方法和测量结果之间存在很大差异。我们的研究建议使用MC方法进行小野肺剂量计算。
Background In this study the accuracy of a pencil beam based treatment planning system (TPS) was evaluated for lung dose calculations by comparison with measurement and the Monte Carlo (MC) method.Aim In the current study we assessed the performance of the Eclipse treatment planning system in the thorax region by ionization chamber measurements and Monte Carlo calculations. We examined two analytic methods: modified Batho (MB) and equivalent tissue-air ratio "ETAR" methods for thorax region irradiadons. For Monte Carlo calculations in the thorax phantom, we modelled a Varian Clinac 2100EX linac. After benchmarking our model with water phantom measurements we used this model for thorax phantom calculations.Materials/Methods 8 and 15MV photon beams of Varian 21EX linac were used for irradiations. Using MANP4C Monte Carlo code, the geometry of the linac head was simulated. After commissioning "MC" beam models, lung doses were calculated by the Monte Carlo (MC) method. Irradiation cases were: ( I) posterior fields of single lung with field sizes of 4x4 and 10x10cm(2) (2) lateral fields of thorax with 4x4 and 10x 10cm(2) field sizes.Results TPS calculations involving ETAR and MB methods were in close agreement with Monte Carlo results and measurements for a 10x10 cm(2) field size at both energies. For a field size of 4x4cm(2) the maximum differences in local dose between TPS calculations and measurement were +33% (MB) and +28% (ETAR). Also, they ignored lung dose reduction due to lateral electronic equilibrium for small field size. Similar results would be expected for other TPSs implementing these algorithms. MC calculations were in excellent agreement with measurement, showing local differences of no more than 2% for all measured points.Conclusions Our study findings showed great differences between both analytical methods and measurements for 4x4cm(2) field sizes for points in the lung. Our study recommends using the MC method for small-field lung dose calculations.