| Objective:By analyzing the error value of image timing for different anatomical structures selected during image-guided radiotherapy for lung cancer patients,the anatomical structure more suitable for online image timing for central and peripheral lung cancer was explored,providing reference for the selection of image timing for lung cancer image-guided radiotherapy image.Methods:43 patients with lung cancer who received chest radiotherapy in our hospital from June 2021 to August 2022 were selected as subjects.All patients were treated with intensity modulated radiotherapy guided by CBCT images.According to the definition of central and peripheral types of lung cancer in the second edition of tumor radiotherapy,they were divided into central and peripheral types of lung cancer according to the distance between tumor location and bronchial tree,great blood vessels,esophagus,trachea,heart,pericardium and vertebral body.Then large aperture CT was used to acquire positioning images and outline target areas in the Eclipse planning system,and the radiotherapy plan was prepared by the physicist.Before treatment,image registration was performed between the images collected by CBCT and planned CT images in the treatment position.29 patients with central lung cancer used thoracic vertebrae,sternum,trachea,tracheal carina,and tumor as anatomical structures,while 14 patients with peripheral lung cancer used thoracic vertebrae,tumor,affected side ribs,and tumor combined with nearby ribs as anatomical structures.Automatic and manual registration methods were used in both groups for offline registration of the first conical beam CT image and location CT image before treatment.The error values of target center position in X(left and right),Y(head and foot),Z(front and back)directions in planned CT image and CBCT image were recorded respectively.One-way analysis of variance and LSD-t test were used for statistical analysis.Results:1.In peripheral lung cancer,the error values on X axis,Y axis and Z axis for image registration with tumor combined with nearby rib,affected side rib,thoracic vertebra and tumor as anatomical structure are as follows:(0.03±0.12),(0.01±0.25),(0.01±0.08);(0.09±0.22),(-0.07±0.14),(-0.02±0.12);(-0.09±0.17),(-0.05±0.16),(-0.16±0.35);(-0.12±0.25),(-0.12±0.13),(-0.17±0.29).The error values of each anatomic marker in X,Y and Z directions were analyzed by one-way variance.The results showed that the error values in X and Z directions were statistically different(F=3.630,P=0.019;F=2.889,P=0.044),there was no significant difference in Y direction(F=1.443,P=0.241).The further analysis of LSD-t test in X and Z directions showed that the differences were mainly reflected in:(1)the tumor group and the affected side rib group,and the rib group near the tumor combination(P < 0.05);(2)Between thoracic vertebra group and affected side rib group(P < 0.05).Pairwise comparison among other groups showed no significant difference(P > 0.05).2.In central lung cancer,the error values of different anatomical markers on X axis,Y axis and Z axis after image registration were as follows:tumor group:(-0.00±0.12),(-0.00±0.14),(-0.00±0.17);Tracheal protrusion group:(0.01±0.10),(0.02±0.10),(-0.00±0.17);Thoracic vertebra group:(0.01±0.12),(-0.02±0.11),(0.03±0.10);Tracheal group:(-0.02±0.16),(0.06±0.20),(-0.04±0.17);Sternum group:(0.06±0.25),(-0.10±0.27),(0.11±0.27).The error values of each anatomic marker in the X,Y and Z directions were analyzed by one-way variance analysis.The results showed that there was no statistical difference in the X direction(F=1.289,P=0.277),but there were differences in the Y and Z directions(F=3.329,P=0.012;F=2.956,P=0.022).Further statistical analysis results of LSD-t test in the Y and Z directions showed that there were statistical differences between the sternum group,tumor group,tracheal group and tracheal carina group(P < 0.05),while pairwise comparison of other groups showed no statistical differences(P > 0.05).Conclusions:1.For peripheral lung cancer,the anatomical structure of tumor combined with nearby ribs was the preferred choice.2.Tracheal carina,thoracic vertebra and trachea can all be used as anatomical structures for central lung cancer images,and tracheal carina or thoracic vertebra are preferred. |
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