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.%目的 观察Body-Fix(R)装置用于脊椎转移瘤大分割调强放疗的误差改变,为广泛开展骨转移大分割治疗提供参考资料.方法 选择2008-2009年在本院接受大分割调强放疗的6例鼻咽癌椎体转移患者,均使用Body-Fix(R)装置进行固定、摆位和治疗.利用千伏级锥形束CT采集放疗前、摆位纠正后、放疗后图像,与计划CT图像进行配准,对摆位纠正后和放疗后位置误差变化情况(分次内误差)进行统计分析.结果 上、中、下段椎体左右方向分次内误差分别为(-0.6±0.5)、(-0.1 ±1.0)、(0.0±0.4)mm,头脚方向分次内误差分别为(1.0±1.4)、(4.8±5.7)、(0.0±0.3)mm,前后方向分次内误差分别为(1.2±5.2)、(-0.3 ±0.3)、(0.0±0.5)mm.结论 采用Body-Fix(R)装置后各节段椎体的分次内误差基本能控制在2 mm内,为采用大分割调强放疗治疗椎体转移瘤提供了良好的固定保障.
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