ABSTRACT
Objective To study the immobilization effect and keep the accurate treating position of Body-Fix (R) device in the patients with vertebral metastatic tumor treated by hypofractionated intensitymodulated radiotherapy.Methods From October 2008 to February 2010,six nasopharyngeal carcinoma patients with 10 treated lesion with vertebral metastasis who were treated by hypofractionated intensitymodulated radiotherapy and immobilized by the Body-Fix (R) device were enrolled in this study.Three sets cone beam CT images were taken and recorded when patient was underway the initial setup,position correction and after radiation delivery.Comparing these images with the planning CT images to get the setup errors and the intrafractional position shifting,and the immobilization effect of Body-Fix (R) device was analyzed.Results In the upper,middle and lower sections of the vertebrae,the intrafractional setup errors in the left-right direction were (-0.6±0.5) mm,(-0.1 ±1.0) mm,(0.0±0.4) mm,with in the superior-inferior direction (1.0 ± 1.4) mm,(4.8 ± 5.7) mm,(0.0 ± 0.3) mm and in the anterior-posterior direction (1.2 ± 5.2) mm,(-0.3 ± 0.3) mm,(0.0 ± 0.5) mm,respectively.Conclusions With Body-Fix (R) device,the intrafractional setup errors can be minimized within 2 mm which make the accurate spinal radiosurgery technique possible.