Plan quality comparison between coplanar and non-coplanar VMAT for the whole brain radiotherapy with hippocampus and hypothalamic-pituitary axis sparing
10.3760/cma.j.cn113030-20231202-00185
- VernacularTitle:共面和非共面VMAT全脑放疗中保护海马及下丘脑-垂体轴的计划质量
- Author:
Keqiang WANG
1
;
Jie CHEN
;
Jianbo JIAN
;
Peng WANG
;
Xinshan ZHANG
;
Hongyang ZHANG
;
Wenxue ZHANG
Author Information
1. 天津医科大学总医院放射治疗科，天津 300052
- Keywords:
Radiotherapy, intensity-modulated;
Volumetric intensity modulated arc therapy;
Coplanar;
Whole brain radiotherapy;
Hippocampus and hypothalamic-pituitary
- From:
Chinese Journal of Radiation Oncology
2024;33(7):634-641
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To compare the plan quality between coplanar and non-coplanar volumetric modulated arc therapy (co-VMAT and nco-VMAT) techniques for the whole brain radiotherapy with hippocampus and hypothalamic-pituitary (HT-P) axis sparing.Methods:A total of 15 patients who underwent prophylactic cranial irradiation in Tianjin Medical University General Hospital from November 2021 to August 2023 were retrospectively selected. The hippocampus and HT-P axis were delineated according to Radiation Therapy Oncology Group (RTOG) 0933 and contouring guidelines for hypothalamus. Co-VMAT and nco-VMAT plans were generated for each patient with a prescription dose of 30 Gy in 10 fractions. Then, dosimetric parameters, plan robustness, plan complexity, and delivery efficiency for both plans were compared using paired t-test. Results:Both co-VMAT and nco-VMAT plans could achieve dosimetric objectives. There were no significant differences in D 2%, D 95% and conformity index (CI) of planning target volume (PTV) between the two plans. The D 98% and homogeneity index (HI) of PTV in co-VMAT showed a slight inferiority compared to that in nco-VMAT (D 98%: 26.37 Gy vs. 26.96 Gy, P=0.001; HI: 0.25 vs. 0.24, P=0.002). The D min of bilateral hippocampus in co-VMAT were 8.55 Gy (left) and 8.32 Gy (right), which were lower than 9.31 Gy (left) and 9.26 Gy (right) in nco-VMAT. In addition, the D mean of the hypothalamus and pituitary in the co-VMAT plan were lower than those in the nco-VMAT plan (hypothalamus: 11.54 Gy vs. 12.27 Gy; pituitary: 11.72 Gy vs.12.1 Gy, both P<0.001). The doses to the hippocampus and HT-P axis were highly sensitive to errors in both co-VMAT and nco-VMAT plans, while the sensitivity of dose to errors in the PTV and other organs at risk was low. The co-VMAT plan had lower complexity compared to the nco-VMAT plan, with γ passing rate at 3%/3 mm criteria of 99.06%±0.60% and 98.05%±2.89%, respectively. The average beam-on time of the co-VMAT plan was 4.8 min, approximately 2/3 of the time for nco-VMAT, while the average treatment time was 6.3 min, approximately half of the treatment time for nco-VMAT. Conclusions:Both co-VMAT and nco-VMAT can achieve hippocampus and HT-P axis sparing in the whole brain radiotherapy. In the co-VMAT plan, the D 98% of the PTV is slightly smaller, but it provides better protection for the hippocampus and HT-P axis. The doses to the hippocampus and HT-P axis are sensitive to errors in both plans. However, the co-VMAT plan has lower complexity, higher delivery efficiency, and is more suitable for clinical treatment.
