The application of 4D-CBCT on accurate radiotherapy of esophageal cancer

GE Xiaolin; LI Jinkai; WANG Peipei; LI Caihong; CHEN Jiayan; CAO Yuandong; ZHANG Sheng; YANG Yan; LI Danming; MU Qingxia; SUN Xinchen

Abstract：Objective To investigate the application of four dimension cone?beam CT( 4D?CBCT) on accurate radiotherapy of esophageal cancer, and provide basis for delineation of planning torget volume( PTV) . Methods Sixteen patients with pathologically confirmed esophageal cancer were included in this study.Each patient received 4D?CBCT based imaging guided analysis once a week. Online CBCT scan,image registration and setup correction were performed before and immediately after radiotherapy. The CBCT images were matched and compared with the images of planning CT automaticly and the setup errors were displayed in the superior?inferior ( SI) , left?right( LR) and anterior?post ( AP ) directions respectively. The setup errors were corrected with remote control before the treatment. Results A total of 166 CBCT scan from 16 patients were obtained during treatment.Under the condition of non?correction, the error were (5?6±0?4)mm,(3?4±0?5)mm, (2?2±0?2)mm in the SI, LR and AP directions, respectively.When the tumor was corrected in every fraction, the error were (1?6±0?2)mm, (0?2±0?1)mm, (0?3±0?2)mm respectively. The margins of target in the SI, LR and AP directions was 7?3mm, 9?4mm, 7?6mm before correction and 3?0mm, 4?6mm, 2?5mm after correction. Conclusion The use of 4D?CBCT correction markedly reduce the impact of setup error. It is feasible to deliver the online image guided radiation for patients with esophageal cancer.