Abstract

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Title:: Dosimetry Verification of Volume Modulated Radiotherapy Plans for Preoperative Rectal Cancer based on Monte Carlo Simulation

Author(s):: YAO Kaining1; YUE Haizhen1; WANG Ruoxi1; WANG Meijiao1; GONG Jian1; GONG Liqing2; ZHANG Yibao1; WU Hao1; 1. Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiotherapy, Peking University Cancer Hospital & Institute, Beijing 100142, China 2. Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Nutrition, Peking University Cancer Hospital & Institute, Beijing 100142, China

Keywords:: Monte Carlo simulation RapidPlan model Gamma 3D analysis volumetric modulated arc therapy anisotropic analytical algorithm

Abstract:: Purpose This work aims to carry out a Monte Carlo based investigation on the precision of dose estimation for Volumetric Modulated Arc Therapy (VMAT) plans based on anisotropic analytical algorithm, focusing on preoperative rectum tumor. Methods 20 VMAT plans of preoperative rectum tumor have been optimized using AAA and RapidPlan model. The precision of RapidPlan estimated dose estimations are evaluated via comparison with independent calculation of dose distribution based on Monte Carlo simulations. The comparison is carried out using several key parameters: mean DVH, Homogeneity Index (HI), Conformity Index (CI), 3D Gamma pass rate. Results 3D Gamma pass rate under two different criteria are 97.58±0.47%、92.46±1.76% for max dose and local dose, respectively，where the difference is statistically significant (P < 0.05) for parameters that do not conform with normal distribution (except for CI of PGTV and Dmin of PTV, where non-parametric test has shown statistical significant difference (P < 0.05) other parameters tested with pair sample t-test all reveal statistical significant difference (P < 0.05).Conclusion The RapidPlan estimation mainly differs in low dose region with MC simulation, which is related to the anisotropic analytical algorithm precision. Mean values of CI and HI in MC simulation are higher than those in RapidPlan estimation. In the meantime, RapidPlan model underestimates Dmean and D50% of femoral head and bladder