Comparison Of Difference Registration Landmarks For CT/MRI Image Fusion And Radiation Plan Forthe Different Target Volume Delineated By CT Or CT/MRI Fusion In The Radiotherapy For Lung Cancer With Post-obstructive Lobar Collapse

ObjectiveTo investigate the impact of anatomical landmarks on registration in CT/MRI image fusion and to study the potential of delineating the target volumes using CT/MRI in the radiotherapy for lung cancer patients with post-obstructive lobar collapse(POLC).MethodsFifty-five lung cancer patients with post-obstructive lobar collapse were enrolled in studyI.Before radiation plan,two sets of simulating images,according to spine registration and pulmonary artery registration,were obtained for each patient using CT/MRI fusion.Comparing the difference of geometric center between the two sets of image by the mean displacement in X,Y,Z directions(X,Y,Z respectively represent the directions of body with left to right,superior to inferior,anter to poster).Thirty-eight patients with enhanced CT sim image can be identified the boundary of tumor.Respectively delineate target volumes and OARs on CT image and optimized CT/MRI fusion image,including GTVct and GTVfu,PTVct and PTVfu.PlanCT and PlanFU were carried out on CT sets with same beam number and direction.Dose distributions of OARs were showed on the basis of DVH.Compare volume target,dose distribution of target and OAR.Results1.The difference inX,Y,Z directions in two sets of simulating images,were 0.283cm,0.255cm,0.175cm.The mean displacement in image according to pulmonary artery less than in image according to spine registration(p<0.05)2.The mean of GTVfu,GTVct is 93.572cm3,120.027 cm3;The mean of PTVfu,PTVct was 490.985cm3,587.811cm3.GTVfu and PTVfu delineated in CT/MRI fusion image less than GTVct and PTVct delineated in CT image(P= 0.000)?3.The DVH comparison showed OARs of PlanFU got less exposure compared to those of PlanCT.In PlanFU,the mean V5,V10 of total lung were 47.377%,37.227%,mean lung dose(MLD)was 1239.847cGy,V30 of heart was 20.612%;In PlanCT,the mean V5,V10 of total lung were 49.623%.38.740%.mean lung dose(MLD)was1289.529 cGy,V30 of heart was23.145%.PlanFU is better than PlanCT(p<0.05).The mean V20 in PlanFU was 20.392%,that was 20.293%in PlanCT(p=0.909).4.GTVfu/LV was 0.032,lessing than GTVct/LV 0.041(p=0.000).Conclusion1.The mean displacement of geometric center in image according to pulmonary artery less than in image according to spine registration.The technology of CT/MR image fusion according to pulmonary artery can help to confirm target volume.2.The mean volume of GTVf was significantly smaller than GTVct,and the outline in the field of GTVct.Confirmed that image fusion quality is better,the images according to pulmonary artery compared with the images according to spine registration.3.CT/MRI fusion is more competent than CT simulation alone,in identifying and defining the borderlines of tumor masses and reducing the exposure of OARs.4.In PlanFU,GTV/LV ratio is smaller than that in PlanCT,lower the risks of RP?2.