The application and correlation study of γ rule and DVH evaluation for VMAT dose verification evaluation of cervical cancer patients
10.3760/cma.j.cn113030-20200927-00480
- VernacularTitle:宫颈癌VMAT剂量验证的γ与DVH评估及两者与剂量偏差相关性研究
- Author:
YangGuang MA
1
;
Rizhen MAI
;
Yuntong PEI
;
Fangna WANG
;
Lele LIU
;
Yuexin GUO
Author Information
1. 郑州大学第一附属医院放射治疗部，郑州 450052
- Keywords:
Dose volume histogram;
Gamma rule;
Dose verification;
Volumetric modulated arc therapy
- From:
Chinese Journal of Radiation Oncology
2022;31(5):450-455
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To evaluate the volumetric modulated arc therapy (VMAT) dose verification of cervical cancer based on γ rule and dose volume histogram (DVH) and to perform correlation analysis between the evaluation results and the dose differences.Methods:Twenty cervical cancer VMAT plans were selected and performed on TrueBeam Linac. The delivered point and surface dose was measured by FC-65 G and ArcCheck and the results were compared to those calculated by Eclipse. The dose of patients was reconstructed by 3DVH. Then, differences between the reconstructed and plan value of D mean, D 95%, D 98% and D 2% of PTV, V 20Gy of left and right femoral head, V 40Gy of rectum, D 1cm 3 of cord, D 98%, D 2% and D 50% of the 50% prescription iso-dose volume (IDV), were evaluated and 3-dimensional (3D) γ was assessed for each organ. Lastly, Pearson’s correlation coefficient was used to analyze the relationship between point dose difference, 2D γ pass-rate (γ%), γ mean and 3D γ% of each organ and the dose difference. Results:Small differences were found between the point dose measured, reconstructed and the plan value. Differences between D mean of PTV, all dose parameters of IDV and plan values were all within 3% and V 40Gy of rectum showed the largest difference. As for the 3D γ%, the maximum pass rate was found for the left and right femoral head and the maximum variance for cord D 1cm 3. There was a moderate correlation between measured and reconstructed point dose deviation and dose difference of each organ, while no significant correlation was found for 2D γ%. Strong correlation was found between 3D γ% of target and D 50% of PTV/IDV and no correlation was found for other organs. Conclusion:The performance of both γ-and DVH-based evaluation can reveal dose error for dose verification, but both of them have some limitations and should be combined in clinical practice.
