The Primary Study Of Evaluating The Precision Of Image Registration Between MRI Simulation And CT Simulation

Objective:To evaluate the precision of image registration between MRI simulation(MRIsim)and CT simulation compared to MRI diagnosis(MRIdiag)and further find the dosimetric effects on target and organs at risk to provide reference for clinical application of MRIsim.Methods:24 patients who underwent both MRIsim and MRIdiag were selected,including 8 gliomas,8 nasopharyngeal carcinomas and 8 prostate cancers.MRIsim and MRIdiag images of each patient were fused with CT respectively.The OARs were delineated on three modalities of images and targets were delineated on fusion image of MRIsim and CT(F_CTMsim)and fusion image of MRIdiag and CT(F_CTMdiag)respectively.The consistency index(CI),shape similarity index(DSC)of OARs and image similarity index(S)of images from MRIsim,MRIdiag and CT were evaluated.IMRT plans were designed based targets from F CTMsim、F CTMdiag and OARs from CT,dosimetric differences of targets and OARs were evaluated subsequently.Results:Volumes of most OAR from three modalities of images showed no significant difference.The CI and DSC of Most OARs from MRIsim compared with CT were significantly higher than those of MRIdiag.The S values of MRIsim and MRIdiag compared with CT were 0.89 and 0.83,respectively(p=0.000,0.000).MRIsim improved the S value by 10%(2%-56%)compared with MRIdiag.No further dosimetric differences were found on all OARs and targets in the three cancers.Conclusions:The precision of image registration can be significantly improved by introducing MRIsim into radiotherapy Compared with MRIdiag.However,no dosimetric differences were found on targets produced by rigid registration and manual adjustment method.