Application of EPID-based in vivo dose verification in dynamic intensity-modulated radiotherapy for lung and esophageal cancers
10.3760/cma.j.cn112271-20230316-00078
- VernacularTitle:基于EPID在体剂量验证在肺癌和食管癌动态调强放疗中的应用研究
- Author:
Jia FANG
1
;
Wanli ZHU
;
Chunyan DAI
;
Xin YANG
;
Hongjuan SUN
;
Yingjie MEI
;
Yanfang LIU
;
Shubo DING
Author Information
1. 浙江省金华市中心医院放疗科，金华 321000
- Keywords:
Electronic portal imaging device;
In vivo dose verification;
Radiotherapy quality control;
Adaptive radiotherapy
- From:
Chinese Journal of Radiological Medicine and Protection
2023;43(9):705-711
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To investigate the factors affecting the accuracy of electronic portal imaging device (EPID)-based in vivo dose verification in radiotherapy for patients with lung and esophageal cancers, and to recommend the workflow and specifications for the application of the in vivo dose verification. Methods:This study randomly selected 32 patients who received radiotherapy for esophageal and lung cancers at the Department of Radiation Oncology, Jinhua Municipal Central Hospital from May to August 2022, including 14 lung cancer cases and 18 esophageal cancer cases. Using a uRT-linac 506c linear accelerator, these patients were treated according to the dynamic intensity-modulated radiotherapy (dIMRT) and EPID-based In vivo dose verification ( In vivo EPID) plans developed with the uRT-TPOIS planning system. The In vivo dose verification performed during the treatment included 238 fractions of In vivo EPID and 80 fractions of image-guided radiotherapy (IGRT) for the lung cancer cases, as well as 414 fractions of In vivo EPID and 105 fractions of IGRT for the esophageal cancer cases. The 2D γ passing rate for each irradiation field was obtained according to the set threshold value. Furthermore, fractioned irradiation fields with γ-passing rates below the threshold value were analyzed, and primary factors decreasing the γ-passing rate were further analyzed by combining the online CT images and 3D reconstruction-derived dose. Results:For lung and esophageal cancers, the mean γ-passing rates were 95.1% ± 5.7% and 96.5% ± 4.5%, respectively at 3 mm/5%; 91.5% ± 8.4% and 92.2% ± 4.9%, respectively at 3 mm/3%, and 79.1% ± 14.7% and 83.7% ± 8.2%, respectively at 2 mm/2%, indicating no statistically significant differences between two cancers ( P > 0.05). The average γ passing rate for beam orientations near 0°/180° (Group A) was higher than those near 90°/270° (Group B) 3 mm/5%: Z = -25.4, P < 0.05; 3 mm/3%: Z = -26.8, P < 0.05). The IGRT correction of setup errors significantly improved the γ passing rates (96.3% ± 5.1% and 96.4% ± 4.9%, respectively at 3 mm/5%, Z = -5.50, P < 0.05; 92.3% ± 8.0% and 91.3% ± 7.7%, respectively at 3 mm/3%, Z = -9.54, P < 0.05). The results of In vivo dose verification were affected by changes in the volumes and motion of tumors and normal tissues, radiotherapy positioning, and adequacy of pre-treatment preparation. Conclusions:EPID-based In vivo dose verification during radiotherapy can avoid incorrect irradiation. However, it is necessary to standardize the workflow of the EPID-based In vivo dose verification to avoid the decrease in the γ passing rate caused by artificial factors.
