真空袋固定摆位两种方法在胸腹部放疗中的比较

Clinical application of vacuum bag immobilization of the trunk in the thorax and abdominal radiotherapy

目的比较放疗中在垂直方向上以升床高度进行摆位与仅以真空袋标识为参考进行摆位,两种方法在垂直方向上产生误差的大小。方法对80例胸腹部常规放疗真空袋固定的肿瘤患者,利用X线模拟定位机在首次放疗前拍摄侧位片为标准,并在放疗末段时分别利用真空袋标识(A组)和升床高度(B组)为摆位参数进行摆位并拍摄其侧位片,分别测量图像中心点与首次摆位时的垂直位移变化,并比较两种方法之间的中心点位移情况。结果以升床高度为参考进行摆位时在垂直方向上与首次模拟机拍摄的X线侧位片产生误差>5mm4例(5%),仅以真空袋标识为参考摆位时,垂直方向上产生误差>5mm14例(17.5%)。结论仅以真空袋标识为参考时摆位偏差明显大于以升床高度摆位偏差;说明在真空袋固定的肿瘤放疗摆位时必须验证升床高度的参数。

[Objective] The measurement error in vertical direction was compared between the immobilized methods of the trunk identified by vacuum bag and height of bed-lifted.[Methods] Lateral X films were taken by X-ray simulatedlocator to record the immobilized position of trunk using the parameters of vacuum bag identification（Group A）or bed-lifted height（Group B）before the first radiotherapy and at the end of radiotherapy in 80 cancer patients who accepted thorax and abdominal radiotherapy immobilized with vacuum bag.The variance of vertical movement were measured and compared before and after the setup.[Results] The variance of movement before and after the setup was 5%（4 cases）in the patients using the identified parameter of bed-lifted height（Group B）,while it was 17.5%（14 cases）in patients only using vacuum bag immobilization.[Conclusions] The variance of movement decreased significantly in the group combined with the identification of bed-lifted height in the clinical application of vacuum bag immobilization,which suggested that the testing of bed-lifted height be needed when using the vacuum bag immobilization in the thorax and abdominal radiotherapy.