Yongbao Li1, Bin Wang1, Shouliang Ding1, Hongdong Liu1, Biaoshui Liu1, Yunfei Xia1, Ting Song2, Xiaoyan Huang3. 1. Department of Radiation Oncology, Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, China. 2. School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China. Electronic address: tingsong2015@smu.edu.cn. 3. Department of Radiation Oncology, Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, China. Electronic address: huangxiaoy@sysucc.org.cn.
Abstract
PURPOSE: To validate the feasibility and accuracy of commonly used collapsed cone (CC) dose engine for Elekta Unity 1.5T MR-LINAC online independent dose verification. MATERIALS AND METHODS: The Unity beam model was built and commissioned in RayStation treatment planning system with CC dose engine. Four AAPM TG-119 test plans were created and measured with ArcCHECK phantom for comparison, another thirty patient plans from six tumor sites were also included. The dosimetric criteria for various ROIs and 3D gamma passing rates were quantitatively evaluated, and the effects of magnetic field and dose deposition type on the dose difference between two systems were further analyzed. RESULTS: ArcCHECK based measurement showed a clear magnetic field induced profile shift between CC with both measurement and GPUMCD. For clinical plans, gamma passing rates with criteria (3%, 3 mm) between GPUMCD and CC large than 90% can be achieved for most tumor sites except esophagus and lung cases, the mean dose difference of 3% can be satisfied for most ROIs from all tumor sites. The magnetic field caused a large dose impact on low density areas, the average gamma passing rates were improved from 85.54% to 96.43% and 87.40% to 99.54% for esophagus and lung cases when the magnetic field effect was excluded. CONCLUSIONS: It is feasible to use CC dose engine as a secondary dose calculation tool for Elekta Unity system for most tumor sites, while the accuracy is limited and should be used carefully for low density areas, such as esophagus and lung cases.
PURPOSE: To validate the feasibility and accuracy of commonly used collapsed cone (CC) dose engine for Elekta Unity 1.5T MR-LINAC online independent dose verification. MATERIALS AND METHODS: The Unity beam model was built and commissioned in RayStation treatment planning system with CC dose engine. Four AAPM TG-119 test plans were created and measured with ArcCHECK phantom for comparison, another thirty patient plans from six tumor sites were also included. The dosimetric criteria for various ROIs and 3D gamma passing rates were quantitatively evaluated, and the effects of magnetic field and dose deposition type on the dose difference between two systems were further analyzed. RESULTS: ArcCHECK based measurement showed a clear magnetic field induced profile shift between CC with both measurement and GPUMCD. For clinical plans, gamma passing rates with criteria (3%, 3 mm) between GPUMCD and CC large than 90% can be achieved for most tumor sites except esophagus and lung cases, the mean dose difference of 3% can be satisfied for most ROIs from all tumor sites. The magnetic field caused a large dose impact on low density areas, the average gamma passing rates were improved from 85.54% to 96.43% and 87.40% to 99.54% for esophagus and lung cases when the magnetic field effect was excluded. CONCLUSIONS: It is feasible to use CC dose engine as a secondary dose calculation tool for Elekta Unity system for most tumor sites, while the accuracy is limited and should be used carefully for low density areas, such as esophagus and lung cases.
Authors: Carolin Rippke; Oliver Schrenk; C Katharina Renkamp; Carolin Buchele; Juliane Hörner-Rieber; Jürgen Debus; Markus Alber; Sebastian Klüter Journal: J Appl Clin Med Phys Date: 2022-01-12 Impact factor: 2.102