食管癌患者螺旋断层治疗的摆位误差分析

摘要

目的 利用TOMO自带的MVCT图像引导系统,分析食管癌患者治疗摆位误差,指导计算CTV到PTV外扩间距.方法 随机抽取2016年间64例在我院接受TOMO治疗的食管癌患者,在每次摆位后行MvCT获得图像,并将其与定位时KVCT图像进行配准.记录患者在x、y、z轴平移和横截位旋转(roll)摆位误差并行t检验或单因素方差分析.利用M=2.5∑+0.78计算PTV的外扩间距.结果 颈段、胸上段、胸中段、胸下段的CTV-PTV外扩间距在x、y、z轴向略有不同;胸上段食管癌患者使用头颈肩膜固定在y轴向平均摆位误差低于体膜固定(P=0.000);体膜固定时第5、6周z轴摆位误差略小于前几周(P=0.036);3秘图像配准模式得出的摆位误差相近(x轴P=0.868,y轴P=0.491,z轴P=0.169,roll方向P=0.985).结论 食管癌患者摆位误差较大,TOMO自带的图像引导系统MVCT可以很大程度减少摆位误差,确保每次治疗精度.同时建议临床上在不同食管癌分段使用不同CTV-PTV外扩间距.胸上段食管癌患者建议使用头颈肩膜来固定.%Objective To analyze setup errors and guide the calculation of margins from clinical target volume (CTV) and planning target volume (PTV) in esophageal cancer patients treated with tomothcrapy by the MVCT image-guided system.Methods Sixty-four esophageal canccr patients trcated with tomotherapy in our hospital in 2016 were randomly selected.MVCT images were acquired after patients' positioning and co-registered with KVCT images.The setup errors of x,y,and z translations and roll rotation were analyzed with the t-test or one-way ANOVA.Meanwhile,PTV margin was calculated based on the formula of M =2.5 Σ + 0.7δ Results According to the formula,the CTV-PTV margins in the x,y and z directions are slightly different between cancers located in the cervical,upper thoracic,middle thoracic,and lower thoracic segments.In patients with upper thoracic esophageal cancer,the average setnp error in the yaxis was lower when the head-neck-shoulder thermoplastic film fixation was used than when somatic thermoplastic film fixation (P=0.000);the setup errors of z-axis with somatic thermoplastic film fixation in the fifth and sixth weeks were slightly less than those in the first several weeks (P =0.036);the setup errors acquired by three image registration patterns were similar (x-axis P=0.868,y-axis P=0.491,z-axis P=0.169,roll P=0.985).Conclusions In the treatment of patients with esophageal cancer,the setup errors are large,but the MVCT in the TOMO HD system can greatly reduce the setup errors,ensuring the accuracy of each treatment.It is further recommended that in clinical practice,different CTV-PTV margins should be used for the treatments of esophageal cancers located in different segments.Patients with upper thoracic esophageal cancer are advised to use the head-neck-shoulder thermoplastic film fixation.