自由呼吸状态下X线平片和CBCT在EB-PBI摆位误差测定与校正的比较研究

摘要

Objective To compare the differences in setup error (SE) assessment and correction between the orthogonal kilovolt X-ray images and CBCT in EB-PBI patients during free breathing.Methods Nineteen patients after breast conserving surgery EB-PBI were recruited.Interfraction SE was acquired using orthogonal kilovolt X-ray setup images and CBCT,after on-line setup correction,calculate the residual error and compare the SE,residual error and setup margin (SM) quantified for orthogonal kilovolt X-ray images and CBCT.Wilcoxon sign-rank test was used to evaluate the differences.Results The CBCT based SE (systematic error,∑) was smaller than the orthogonal kilovolt X-ray images based ∑ in AP direction (-1.2 mm vs 2.00 mm; P =0.005),and there was no statistically significant differences for three dimensional directions in random error (σ) (P =0.948,0.376,0.314).After on-line setup correction,CBCT decreases setup residual error than the orthogonal kilovolt X-ray imagesin AP direction (∑:-0.20 mm vs 0.50 mm,P =0.008 ; σ:0.45 mm vs 1.34 mm,P =0.002).And also the CBCT based SM was smaller than orthogonal kilovolt X-ray images based SM in AP direction (∑:-1.39 mm vs 5.57 mm,P =0.003 ;σ:0.00 mm vs 3.2 mm,P =0.003).Conclusions Compared with kilovolt X-ray images,CBCT underestimate the setup error in the AP direction,but decreases setup residual error significantly.An image-guided radiotherapy and setup error assessment using kilovolt X-ray images for EB-PBI plans was feasible.%目的 对比研究EB-PBI患者自由呼吸状态下正交X线平片和CBCT测得的摆位误差、摆位残差的差异.方法 选择保乳术后EB-PBI患者19例,基于校正前后CBCT图像、正交X线平片分别获取三维方向摆位误差及校正后摆位残差.Wilcoxon符号秩和检验两种方法差异.结果 CBCT、正交X线平片的分次间摆位误差的系统误差仅前后方向不同(-1.2、2.0 mm,P=0.005),随机误差在三维方向均相近(P=0.948、0.376、0.314).与正交X线平片相比CBCT降低了前后方向摆位残差(系统误差-0.2、0.5 mm,P=0.008,随机误差0.5、1.3 mm,P=0.002).校正前后CBCT的摆位误差在前后方向均明显小于X线平片(系统误差-1.4、5.6 mm,P=0.003,随机误差0.0、3.2mm,P=0.003).结论 与CBCT相比,正交X线平片增加了发现前后方向摆位误差的能力,但CBCT的摆位残差降低更明显.对EB-PBI患者X线平片获取时间短、辐射量低且摆位验证精度可信,适用于IGRT或摆位误差分析.