Abstract：Objective To study the role of KV CBCT on the geometrical accuracy of three-dimensional conformal radiotherapy (3DCRT) and to evaluate the margin of targets and peripheral OAR for thoracic carcinoma. Methods 34 patients with thoracic carcinoma were enrolled. Varian-IX liuac with OBI system was used to acquire CBCT scans before delivery in 3DCRT. The left-right (x), superior-inferior (y), anterior-posterior (z) setup errors of patients can be obtained from the tomography images automatically restructured by the system. Results According to 279 CBCT scans the systemic ±random error on x, y, z directions were (-0.16± 3.25) mm,(-1.36±5.43) mm,(－2.43±2.14) mm and (2.41±2.18) mm,(4.27±3.60) mm,(2.71±1.77) mm respectively if we do not consider the direction of setup errors. The margins of targets were calculated as 2.68 mm, 7.19 mm and 7.57 mm respectively. Conclusions Setup errors are unavoidable in thoracic carcinoma irradiation.We suggest a PTV margin of 2.68 mm, 7.19 mm and 7.57 mm in the left-right, superior-inferior and anterior-posterior directions respectively in our department.
Cao Xiaohui,Liu Ming,Zhai Fushan et al. Analysis of setup errors and margin for thoracic carcinoma radiotherapy with cone-beam CT-based image guidance[J]. Chinese Journal of Radiation Oncology, 2014, 23(1): 53-55.
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