Abstract：ObjectiveTo analyze the inter-and intra-fractional setup errors of thoracic tumors using kilovolt-image guided radiotherapy (kV-IGRT),and to study the influence of kV image guidance on the accuracy of intensity modulated radiotherapy(IMRT)of thoracic tumors.Methods10 patients with thoracic tumors in our hospital from March to October in 2016 were selected,and the Varian Novalis Tx Linear Accelerator with on board image (OBI)system was used for daily image scanning before radiotherapy,if the bed needs to be moved,image scanning after the moving bed and scanning after radiotherapy was carried out.After the automatic reconstruction of the scanned image,the CT image of the treatment plan was registered,and the setup error of the patient′s Vrt,Lng,Lat were obtained and analyzed statistically.Results688 sets of images were obtained,the pre-radiotherapy setup error of Vrt,Lng,Lat were (-0.03±2.06),(0.16± 2.69),(0.18±2.28)mm,respectively.The setup error after the moving bed were(0.65±0.92),(0.65±0.93),(0.61±0.80)mm,respectively.The post-radiotherapy setup error were (-0.08±1.12),(0.32±1.13),(0.16±1.08)mm,respectively.ConclusionDaily kV-IGRT can significantly reduce the setup error of radiotherapy for thoracic tumors,and is of great significance for improving the accuracy of IMRT for thoracic tumors.
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