Objective To compare the error differences of two position placement fixed way in the process of the application of CBCT image guided radiotherapy in patients with nasopharyngeal carcinoma(NPC).Methods112 cases of patients which were selected from March 2014 to June 2016 line with nasopharyngeal carcinoma radiotherapy,the objects were divided into A and B group according to the random number method,56 cases in each group. Two groups of patients were guided radiotherapy in CBCT images,IMRT position adopt fixed head and neck shoulder thermoplastic film,on the basis of group A fixed joint vacuum air cushion,B in combination with the traditional fixed headrest. The two groups of patients in three dimension beam position and rotating relative error and absolute error were compared,analysis of two groups of patients in four weeks the positioning error on the X axis relationship with the time was conducted.Results 1~2 weeks in group A(vacuum air cushion + head and neck shoulder thermoplastic film fixed)patients in the X,Y,Z three dimensions on bit error and rotation error were significantly less than group B(head + head and neck shoulder thermoplastic film fixed), difference had statistical significance(P<0.05). Two groups of patients with X dimension on bit error in 1~2 weeks had significant difference(P<0.05), there was no statistically significant difference in 3~4 weeks(P>0.05),trend chart visible observation group placement error increased gradually,the control group decreased gradually. The total effective rate(92.86%)was significantly higher in the group A than in the group B(78.57%),the difference was statistically significant(P=0.03).Conclusions Vacuum air cushion + head and neck shoulder thermoplastic film fixed can effectively reduce the positioning error in patients with nasopharyngeal carcinoma radiotherapy,its progress with time gradually rise,beam position error through effective intervention can improve the accuracy of radiotherapy,is worth popularizing in clinical.%目的 研究鼻咽癌(NPC)患者应用CBCT图像引导下放疗过程中两种体位固定方式摆位误差的比较差异.方法 选取2015年3月至2016年9月行放射治疗的NPC患者112例,依照随机数字法分为A、B组,每组各56例.两组患者均在CBCT图像引导下行放射治疗,IMRT体位均采用头颈肩热塑膜固定,在此基础上A组联合真空气垫固定,B组联合传统头枕固定.比较两组患者在三个维度摆位的摆位误差、摆位外扩边界值(MPTV)以及并发症.结果 A组(真空气垫+头颈肩热塑膜固定)患者在X、Y、Z三个维度上摆位误差显著小于B组(头枕+头颈肩热塑膜固定),旋转误差明显大于B组患者,差异比较有统计学意义(P<0.05);两组患者X维度上摆位误差在第1~2周均有显著差异(P<0.05),3~4周差异无统计学意义(P>0.05),趋势图可见观察组摆位误差逐渐增大,对照组逐渐减小.A组患者治疗总有效率(92.86%)明显高于B组(78.57%),差异有统计学意义(P=0.03).结论 真空气垫+头颈肩热塑膜固定能有效降低NPC患者放疗的摆位误差,其X轴摆位误差随时间进展逐渐上升,值得在临床推广.
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