Comparison between electronic portal imaging device (EPID) and cone-beam CT (CBCT) in image-guided thoracic tumor radiotherapy

Objective To compare the set-up error detected by electronic portal imaging device (EPID) with cone-beam CT (CBCT) for patients with thoracic tumor, and to explore the impact on the workflow of different imaging-guided device. Methods From Mar 2007 to Jan 2008, 17 patients with pathologically confirmed thoracic tumor, including lung, esophagus and thymoma, were included in this study. Each patient received both EPID based-CBCT based-imaging-guided analysis once a week. Results A total of 81 pairs of EPI and CBCT scan from 16 patients except one case were obtained during treatment. Compared with EPID based-imaging guided analysis, CBCT based-imaging guided analysis did not increase the total treatment time significantly. The average set-up error of EPID was (- 0.1 ± 3.2), (1.3 ± 3.7) and (-0.2 ± 3.1) mm in the left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions, respectively ( ± SD). But the average set-up error,while that of CBCT was (0.1 ± 4.6), (0.6 ± 4.0) and ( - 0.9 ± 4.6) mm in the LR, SI and AP directions, respectively. Conclusions CBCT would be better than EPID in detecting set-up error of the thoracic tumor patients. Compared with EPID, CBCT based-imaging guided analysis could not influence the workflow of radiotherapy significantly. CBCT based-imaging guided analysis might be more efficient than EPID. Key words: Image-guided radiotherapy;  Electronic portal imaging device;  Kilovoltage cone-beam CT; Thoracic tumor;  Set-up error;  Workflow