Technology Department, Scientific Instrumentation Division, Medical Applications Unit, Centro de Investigaciones Energéticas, MedioAmbientales y Tecnológicas (CIEMAT), Madrid, Spain.
Phys Med Biol. 2018 Jan 25;63(3):035007. doi: 10.1088/1361-6560/aaa2b0.
We have verified the GAMOS/Geant4 simulation model of a 6 MV VARIAN Clinac 2100 C/D linear accelerator by the procedure of adjusting the initial beam parameters to fit the percentage depth dose and cross-profile dose experimental data at different depths in a water phantom. Thanks to the use of a wide range of field sizes, from 2 × 2 cm to 40 × 40 cm, a small phantom voxel size and high statistics, fine precision in the determination of the beam parameters has been achieved. This precision has allowed us to make a thorough study of the different physics models and parameters that Geant4 offers. The three Geant4 electromagnetic physics sets of models, i.e. Standard, Livermore and Penelope, have been compared to the experiment, testing the four different models of angular bremsstrahlung distributions as well as the three available multiple-scattering models, and optimizing the most relevant Geant4 electromagnetic physics parameters. Before the fitting, a comprehensive CPU time optimization has been done, using several of the Geant4 efficiency improvement techniques plus a few more developed in GAMOS.
我们通过调整初始束参数的过程来验证了一个 6 MV 的瓦里安 Clinac 2100 C/D 线性加速器的 GAMOS/Geant4 模拟模型，以拟合水模中不同深度处百分深度剂量和横截面剂量的实验数据。得益于使用了从 2×2cm 到 40×40cm 的大范围射野尺寸、小体模体素大小和高统计量，我们实现了对束参数的精细精确确定。这种精度使我们能够深入研究 Geant4 提供的不同物理模型和参数。我们将三种 Geant4 电磁物理模型集，即标准、利弗莫尔和佩内洛普，与实验进行了比较，测试了四种不同的角韧致辐射分布模型以及三种可用的多次散射模型，并优化了最相关的 Geant4 电磁物理参数。在拟合之前，我们使用了几种 Geant4 效率改进技术以及在 GAMOS 中开发的一些技术，进行了全面的 CPU 时间优化。
