Analysis Of The Setup Error Of Radiotherapy After Breast Conserving Surgery For Breast Cancer Guided By CBCT Image

Objective :The setup error of breast cancer patients in IGRT was measured by CBCT,and the analysis was carried out.Of cone beam CT in breast cancer protection in radiation therapy after breast conserving surgery application value,the basis for breast cancer radiotherapy provides quality assurance and quality control,to achieve precise radiotherapy to provide technical support.Methods:Application of CBCT in 20 patients with breast cancer before and after radiotherapy.According to the actual situation of patients choose appropriate standard headrest,supine position,crossed hands hold the elbow placed in the forehead,the vacuum negative pressure pad is fixed,in the surface marked breast,and paste the wire marker,surgical scar also posted wire marker.To use wire were labeled supraclavicular margin and breast folds 2cm,select setup center,general for center,papillary layer and axillary midline interchange and in three dimensional cross laser indicator on the body surface annotation the center point of the three "+" words,then the three opaque lead bit attached to the three "+" word Center,Using Philips large aperture of 16 row spiral CT simulation location machine down CT scan of the chest,so that patients in the quiet breathing CT scans were performed in,layer spacing 3mm,the scanning range for thyroid cartilage on the margin to the breast folds under 2.0cm.Then the patients were scanned image is transmitted to the XIO treatment planning workstation,registration confirmation by the clinicians were the outline of the target area and normal organs.After inverse planning design,were calculated for set up three dimensional coordinates;output three-dimensional direction,(x axis)shifted to the right for "+" shift to the left "-",(Y axis)move to the "+" downward to "-",before and after(Z axis)before moving to the "+" downward to "-",and for the record.Transfer treatment plan to Varian linear accelerator for radiation therapy.Will get the CBCT image and plan CT image matching,get around(X),head and foot(Y),and after(Z)3 directions of the position error,the error is corrected after the exact treatment.Results :Patients after verification of IGRT,mean errors were reduced.The results show that X and Z axes is similar,the Y axis different different weeks of treatment for IGRT treatment before average pendulum position error in X,y and Z axis are similar to,no significant difference(P > 0.05).20 cases of patients after verification of IGRT,all directions before treatment,the results showed that,after X and Z axes is similar,Y axis different(P = 0.00),which with each IGRT treatment front and back swinging bit error results are similar.In this study,the X axis(4.60 ± 0.18)was reduced to(1.64 ± 0.16)(P = 0.83),and the Y axis(5.57±0.57)was reduced to(1.73±0.17),(P=0.00),The Z axis was reduced to(0.31±0.31)(P=0.86),Thus it can be seen that the Y axis direction error is the biggest,the X,z direction of the position error is small.Conclusion :CBCT image guided radiation therapy for breast cancer after breast conserving surgery can be performed in a timely manner to correct the error.CBCT image guided to adjust the position error is significant,can improve the precision of treatment,breast cancer breast conserving surgery in the direction of the error with the Y axis of the most significant.