Objective:To analyze the verification of Trilogy Varian linear accelerator system on tumor position of head and neck,chest and abdomen under electronic portal imaging device (EPID) mode and cone beam computed tomography (CBCT) mode of intensity modulated radiotherapy (IMRT),so as to confirm the most suitable body parts of verification plan of tumor position. Methods:The case data of 48 patients with tumor who underwent IMRT treatment on tumor at the Second Affiliated Hospital of Xi'an Jiaotong University from October 2022 to October 2023 were selected,which could be divided into tumor at head and neck (16 cases),tumor at chest (16 cases) and tumor at abdomen (16 cases),and all of them were intervened 5 times per week by IMRT. They received 3 times of verification of EPID and CBCT modes per week. The positioning deviation on three dimensional (3D) axis position included x (left and right),y (up and down) and z (head and foot) was evaluated. The verification of CBCT mode conducted automatic registration of grayscale registration method for receiving irradiation area (target area) with dose through the corresponding registration software of OBI system,and the target area and the adjacent area were registration area,and the diagnostic CT image obtained from the design of radiotherapy plan was used as reference image. The positioning deviations on 3D axis positions (x direction,y direction and z direction) of referred image and collected image were calculated by using statistic method. The application values of two verification plans of EPID and CBCT modes on tumor positions were compared. Results:There was no statistically significant in the verification effect of the position of patients with tumor on head and neck between CBCT and EPID of IMRT (P>0.05). Compared with positioning error of EPID mode,that of CBCT mode on x axis was smaller,but the difference was not statistically significant (P>0.05). In the position verification of patients with tumor on chest,the positioning errors of x,y and z axis of CBCT mode of IMRT were respectively less than those of EPID mode,and the differences were significant (t=4.546,15.445,15.961,P<0.05). In the position verification of patients with tumor on abdomen,the positioning errors of x,y and z axis of CBCT mode of IMRT were respectively less than those of EPID mode,and the differences were significant (t=30.402,11.766,12.047,P<0.05). Conclusion:EPID and CBCT modes have equal positioning errors in position verification of IMRT for tumor of head and neck,and the CBCT verification should be prioritized for tumors of chest and abdomen.
Intensity modulated radiotherapy (IMRT)Electronic portal imaging device (EPID)Cone-beam computed tomography (CBCT),Verification of tumor position
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