摘要
Abstract
Objective To analyze the setup errors using on board imager(OBI) system in nasopharyngeal carcinoma treated by intensity modulated radiotherapy. Methods Varian-21EX linear accelerator was used for medical treatment of 38 nasopharyngeal carcinoma cases. Cone-beam computed tomography(CBCT) images were taken by OBI system before the first intensity modulated radiotherapy, once a day for the first 3 days, once a week later, and the translation and rotation errors between were obtained by matching the CBCT images and the planning CT images. Results The average errors obtained from the first scan included right-left (-0.49±1.90) mm, head-feet (0.64+1.36) mm, anteriority-posterior (-0.57± 1.78) mm, and rotation (0.05±0.11) °. After the correction for the first time, the setup errors were all reduced, including right-left (0.30±1.01) mm, head-feet (0.12±0.92) mm, anteriority-posterior (0.47 ±1.05) mm, and rotation (-0.02±0.03) °. Conclusion The setup errors verified by using OBI system can improve the positioning accuracy, and reduce the irradiation amount for surrounding normal tissues. For the intensity modulated radiotherapy of nasopharyngeal carcinoma, the putting boundary is about 2mm from the clinical target volume(CTV) to the planning target volume(PTV). [Chinese Medical Equipment Journal,2011,33(3):64-65]关键词
摆位误差/OBI/调强放射治疗Key words
setup error/on board imager/intensity modulated radiotherapy分类
医药卫生
