应用锥形束CT校正宫颈癌调强放疗摆位误差的研究

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

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 com-puter 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、5.6mm。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。

Objective To 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.Methods Cervical cancer patients treated by Intensity-modulated radiotherapy,were divided into group A（BMI≥24） and group B（BMI24）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..Results Setup 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）.Conclusion CBCT 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.