Individual volume-based 3D gamma indices for pretreatment VMAT QA.
Although gamma analysis is still a widely accepted quantitative tool to analyze and report patient-specific QA for intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT), the correlation between the 2D percentage gamma passing rate (%GP), and the clinical dosimetric difference for IMRT and VMAT has been questioned. The purpose of this study was to investigate the feasibility of individual volume-based 3D gamma indices for pretreatment VMAT QA. Percentage dosimetric errors (%DE) of dose-volume histogram metrics (includes target volumes and organ at risks) between the treatment planning system and QA-reconstructed dose distribution, %GPs for individual volume and global gamma indices, as well their correlations and sensitivities were investigated for one- and two-arc VMAT plans. The %GPs of individual volumes had a higher percent of correlation with individual 15 %DE metrics compared with global %GPs. For two-arc VMAT at 2%/2 mm, 3%/3 mm, and 4%/4 mm criteria, individual volume %GPs were correlated with 9, 12, and 9 out of 15 %DE metrics, while global %GPs were correlated with only 2 out of 15 %DE metrics, respectively. For one-arc VMAT at 2%/2 mm, 3%/3 mm, and 4%/4 mm criteria, individual volume %GPs were correlated with 18, 16, and 13 out of 23 %DE metrics, and global %GPs were correlated with 19, 12, and 1 out 23 %DE metrics, respectively. The area under curves (AUC) of individual volume %GPs were higher than those of global %GPs for two-arc VMAT plans, but with mixed results for one-arc VMAT plans. In a conclusion, the idea of individual volume %GP was created and investigated to better serve for VMAT QA and individual volume-based %GP had a higher percent of correlation with DVH 15 %DE metrics compared with global %GP for both one- and two-arc VMAT plans.
Department of Radiotherapy and Chemotherapy, The 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
Jinling
J
Yi
Department of Radiotherapy and Chemotherapy, The 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
Ce
C
Han
Department of Radiotherapy and Chemotherapy, The 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
Xiaomin
X
Zheng
Department of Radiotherapy and Chemotherapy, The 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
Yongqiang
Y
Zhou
Department of Radiotherapy and Chemotherapy, The 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
Zhenxiang
Z
Deng
Department of Radiotherapy and Chemotherapy, The 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
Congying
C
Xie
Department of Radiotherapy and Chemotherapy, The 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
Xiance
X
Jin
Physics Unit, Department of Radiation Oncology, Chongqing Cancer Hospital & Institute, Chongqing, China.
Fu
F
Jin
D005240:Feasibility Studies; D005720:Gamma Rays; D006801:Humans; D058958:Organs at Risk; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated
percentage dosimetric errors; percentage gamma passing rate; quality assurance; volumetric-modulated arc therapy