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Effect of the rotation errors on the γ pass rate of volume-modulated arc therapy plan in rectal cancer
Qi Wang1, Lian Gong2, Wenguang Yan3
1Department of Oncology, Third Xiangya Hospital, Central South University, Changsha 410013. 15069436@qq.com.
Objectives:
To study the effect of rotation errors on the γ pass rate of volume-modulated arc therapy (VMAT) plan in rectal cancer based on the ArcCheck phantom.
Methods:
CT data from 20 rectal cancer patients underwent VMRT were selected randomly for this study. Targeting areas were selected, and clinical radiotherapy and validation plans were formulated. ArcCheck model was selected to validate the radiotherapy plans. The effect of the rotation errors on the dosimetric verification for VMAT in rectal cancer was simulated and analyzed with ArcCheck model software.
Results:
When there was no rotation errors, the γ pass rate of VMRT plans was more than 95%. When the absolute rotation angle was less than or equal to 1°, the γ pass rate of VMAT plans was more than 90%, meeting the clinical requirements. When the absolute rotation angle was greater than 1°, the γ pass rate was less than 90%, which did not meet clinical requirements.
Conclusions:
The rotation errors affect the γ pass rate of VMAT plans. The larger the rotation angle, the lower the γ pass rate. It meets clinical requirements when the rotation error is less than or equal to 1°.
