Comparison of orthogonal kilovolt X-ray images and cone-beam CT matching results in setup error assessment and correction for EB-PBI during free breathing
Wang Wei*, Li Jianbin, Hu Hongguang, Ma Zhifang, Xu Min, Fan Tingyong, Shao Qian, Ding Yun
*Departmentof Radiation Oncology, Shandong Cancer Hospital& Institute, Ji′nan 250117, China
Abstract：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, Σ) was smaller than the orthogonal kilovolt X-ray images based Σ 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 (Σ:－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 (Σ:－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.
Wang Wei,Li Jianbin,Hu Hongguang et al. Comparison of orthogonal kilovolt X-ray images and cone-beam CT matching results in setup error assessment and correction for EB-PBI during free breathing[J]. Chinese Journal of Radiation Oncology, 2014, 23(2): 147-149.
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2014, Vol. 23 
