应用锥形束CT校正宫颈癌调强放疗摆位误差的研究

目的 应用锥形束CT实时在线校正宫颈癌调强放疗的摆位误差,确定宫颈癌患者外照射治疗计划中外扩边界值的范围,并分析体质量差别对摆位的影响.方法 调强放疗的宫颈癌患者按体质量指数(body mass index,BMI)分为A组(BMI≥24)和B组(BMI＜24),将所获得锥形束CT(cone-beam computer tomography,CBCT)与计划CT图像进行灰度自动配准,计算摆位误差并进行在线评价.结果37例患者在X轴(左右)、Y轴(头脚)、Z轴(前后)方向摆位误差分别为(1.1±2.3)、(2.1±5.0)、(-1.1±2.2)mm,外扩边界分别为5.2、11.0 、5.6 mm.A组患者在Y轴方向摆位误差较B组增大,差异有统计学意义(P＜0.05).而两组在X轴、Z轴方向差异无统计学意义(P＞0.05).结论 应用锥形束CT在线校正可减小宫颈癌患者摆位误差、提高放疗的精确性,可利用摆位误差估算放疗摆位外扩边界值.体质量指数大者应适当增加外扩边界.

Study on Setup Errors Correction Using Cone-beam Computer Tomography in Intensity Modulated Radiotherapy for Cervical Cancer

ObjectiveTo study setup errors correction through the image guided real-time online in intensity-modulated radiotherapy,calculate external radiation therapy the margin ranges,and analyze weight difference influence on setup in cervical cancer patients.MethodsCervical cancer patients treated by Intensity-modulated radiotherapy,were divided into group A (BMI≥24) and group B (BMI＜24)according to the body mass index.Obtained CBCT and planning CT images were automatically registered in gray scale,and setup errors were calculated and evaluated online..ResultsSetup errors of 37 patients in the X axis (left-right),the Y axis (head-foot) and Z axis (superior-inferior) direction were (1.1±2.3),(2.1±5.0) and (1.1±2.2) mm respectively,and the margins in X,Y and Z axis were 5.2mm,11.0mm and 5.6 mm respectively.Setup errors in group A in the Y axis direction was larger than those in group B,P＜0.05.And the differences in both X axis and Z axis were not statistically significant between two groups (P＞0.05).ConclusionCBCT online correction could reduce the cervical cancer patients setup errors,improve the accuracy of radiotherapy and estimate the margins.In patients with increased Body mass index,radiotherapy margins should be appropriately expanded.