Sadoughi Hamid-Reza, Nasseri Shahrokh, Momennezhad Mahdi, Sadeghi Hamid-Reza, Bahreyni-Toosi Mohammad-Hossein
Department of Medical Physics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
Department of Medical Physics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran ; Medical Physics Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
J Med Signals Sens. 2014 Jan;4(1):10-7.
Radiotherapy dose calculations can be evaluated by Monte Carlo (MC) simulations with acceptable accuracy for dose prediction in complicated treatment plans. In this work, Standard, Livermore and Penelope electromagnetic (EM) physics packages of GEANT4 application for tomographic emission (GATE) 6.1 were compared versus Monte Carlo N-Particle eXtended (MCNPX) 2.6 in simulation of 6 MV photon Linac. To do this, similar geometry was used for the two codes. The reference values of percentage depth dose (PDD) and beam profiles were obtained using a 6 MV Elekta Compact linear accelerator, Scanditronix water phantom and diode detectors. No significant deviations were found in PDD, dose profile, energy spectrum, radial mean energy and photon radial distribution, which were calculated by Standard and Livermore EM models and MCNPX, respectively. Nevertheless, the Penelope model showed an extreme difference. Statistical uncertainty in all the simulations was <1%, namely 0.51%, 0.27%, 0.27% and 0.29% for PDDs of 10 cm(2)× 10 cm(2) filed size, for MCNPX, Standard, Livermore and Penelope models, respectively. Differences between spectra in various regions, in radial mean energy and in photon radial distribution were due to different cross section and stopping power data and not the same simulation of physics processes of MCNPX and three EM models. For example, in the Standard model, the photoelectron direction was sampled from the Gavrila-Sauter distribution, but the photoelectron moved in the same direction of the incident photons in the photoelectric process of Livermore and Penelope models. Using the same primary electron beam, the Standard and Livermore EM models of GATE and MCNPX showed similar output, but re-tuning of primary electron beam is needed for the Penelope model.
对于复杂治疗计划中的剂量预测，放射治疗剂量计算可通过蒙特卡罗（MC）模拟进行评估，其精度可接受。在本研究中，将GEANT4断层发射应用程序（GATE）6.1的标准、利弗莫尔和佩内洛普电磁（EM）物理包与蒙特卡罗N粒子扩展程序（MCNPX）2.6在6 MV光子直线加速器模拟中进行了比较。为此，两个代码使用了相似的几何结构。使用6 MV医科达紧凑型直线加速器、扫描电子束水模体和二极管探测器获得了百分深度剂量（PDD）和射野轮廓的参考值。分别由标准和利弗莫尔EM模型以及MCNPX计算得到的PDD、剂量分布、能谱、径向平均能量和光子径向分布未发现显著偏差。然而，佩内洛普模型显示出极大差异。所有模拟中的统计不确定性均<1%，即对于10 cm(2)×10 cm(2)射野尺寸的PDD，MCNPX、标准、利弗莫尔和佩内洛普模型的统计不确定性分别为0.51%、0.27%、0.27%和0.29%。不同区域的能谱、径向平均能量和光子径向分布之间的差异是由于不同的截面和阻止本领数据，以及MCNPX和三个EM模型的物理过程模拟不同。例如，在标准模型中，光电子方向是从加夫里拉 - 绍特分布中采样的，但在利弗莫尔和佩内洛普模型的光电过程中，光电子沿入射光子的相同方向移动。使用相同的初级电子束，GATE的标准和利弗莫尔EM模型与MCNPX显示出相似的输出，但佩内洛普模型需要重新调整初级电子束。
