Objective To analyze the set-up errors of EPID and CT on rail system in image-guided radiation therapy (IGRT) for cervical cancer and evaluate the application value of CT on rail system in IGRT for cervical cancer.Methods 15 patients with cervical cancer were selected in the study.EPID images and CT on rail images were taken once a week.We obtained different set-up errors in X,Y,Z axis though comparing EPID images with the DDR,matching CT on rail images with planned CT images by grey alignment and bone alignment.Finally,we had the three sets of data for statistical analysis.Results Compared with EPID group,the set-up errors of grey alignment group were significantly reduced (P<0.05),and those of bone alignment group in Y and Z axis were also significantly lessened (P<0.05).Besides,the set-up errors of grey alignment group in X,Y axis were less than those of bone alignment group,especially in Y axis (P<0.05).Conclusion CT on rail system is better than EPID in measuring the set-up errors in IGRT for cervical cancer,which made the target more accurate.During the IGRT for cervical cancer guided by CT on rail,grey alignment was better than bone alignment.%目的 比较宫颈癌图像引导放射治疗(IGRT)中滑轨CT(CT on rail)与电子射野影像(EPID)测量的摆位误差,评价CT on rail在宫颈癌IGRT中的应用价值.方法 选取进行宫颈癌IGRT的病人15例,每周扫描一次EPID正侧位片和CT on rail图像,将EPID拍摄的正侧位片与数字重建影像系统(DRR)进行配准,CT on rail图像进行灰度配准和骨性配准,得出三组X(左右)、Y(头脚)、Z(腹背)方向上的线性摆位误差,最终对三组数据进行统计学分析.结果 CT on rail灰度配准组所测摆位误差均明显小于EPID组 (P<0.05);骨性配准组Y、Z轴的摆位误差明显小于EPID组(P<0.05),灰度配准组在X、Y轴的摆位误差较骨性配准组缩小,尤其在Y轴上(P<0.05).结论 在宫颈癌IGRT中,CT on rail较EPID 能更好地测量摆位误差,使放疗靶区更精准;在采用CT on rail引导宫颈癌IGRT时,灰度配准优于骨性配准.
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