Image-guided radiotherapy improves the precision of hypofractionated radiotherapy for thoracic and abdominal tumors / 中华放射肿瘤学杂志

ABSTRACT

Objective To study image-guided hypofractionated radiotherapy for thoracic and abdominal tumors,and to determine the margins extended from internal target volume(ITV) to planning target volume(PTV). Methods Twenty-four patients who received image-guided hypofractionated radiotherapy for thoracic and abdominal tumors were included in this study. X-ray cone beam CT was regularly performed before the treatment. The shift and Rotation in right-left ( R-L), superior-inferior(S-I) and anterior-posterior (A-P) directions were recorded and analyzed. The shift margin from ITV to PTV was calculated with the equation,margin =2'mean+0.7'standard deviation. Results Before online correction,the shift errors in R-L,S-I and A-P directions were [2.1±2.0] mm, [3.9±3.2] mm and [2.9±2.8] mm,and the corresponding margins were 5.6 mm, 10.2 mm and 7.7 mm. After the correction the shift errors were [0.8±0.7] mm, [0.9±0.7] mm and [0.9±0.7] mm, and the margins were 2.1 mm,2.3 mm and 2.3 mm. The set-up error was markedly decreased after the correction. There was no change in rotation after the correction. Conclusions The positioning error decreases after the correction in IGRT,and the precision of radiotherapy is improved. Measuring set-up error in radiotherapy can provide institution-specific margins for PTV designing.