Value of vacuum bag and set-up errors of two different immobilization techniques during pelvic irradiation

Objective: To investigate the value of vacuum bag and the effectiveness of two different immobilization techniques during pelvic irradiation. Methods: Thirty patients with malignant tumor were divided into three groups: non-immobilization group, pelvic immobilization group and legs immobilization group. Simulation films and portal films in anterior-posterior and lateral view were taken and compared. Results: Comparing with non-immobilization, vacuum bag device significantly reduced the set-up errors in left-right, antero-posterior and 3-dimensional vectors except the cranio-caudal vector (P < 0.05). Comparing with pelvic immobilization, legs immobilization significantly reduced the set-up errors of anterior-posterior vector (P < 0.05). Conclusions: Vacuum bag , especially by immobilizing the legs , is able to reduce the set-up error during pelvic irradiation