An Study Of The Evaluation Of Different Parameters Describing The Cerebral State At Superacute Phase Of Infarction Using7T MRI

Objective:To Compare the value of DWI,DTI,T2WI,MRA and DTT in the superacute phase of cereral infarction.Methods:Middle cerebral artery occlusion model of rats,perfoming the MRI examination including MRA,DWI,DWI,T2WI using the7.0T animal machine at30min,3h,6h,9h,12h after the surgery respectively.Then maps of the DCavg ang FA were obtained by using the software of Diffusion Toolkit0.6.2.1.Soon after finishing the MRI scanning head-breaking was proceeded for the acquisition of the brain of the rats, cerebella and the rhinencephalon wered removed,after the brain was freezed to adequte hardness,then the brain was coronally cut into2mm thick slices following TTC staining,10%formalin of fixation. After24hours later the postischemic changes were observed.Measureing the lesion volume of DWI,DCavg maps,T2WI using interactive segmentation algorithm,and comparing the lesion volume with the abnomal volume of TTC.The slice which contained the largest ischemic lesion represented as high signal in DWI was chosen,then thirteen lmm3ROIs at fixed positions were piched.From all the ROIs in the affected side2were chosen from core and margin respectively,then DCavg and FA were measured using the software MRIcrol,and the ralative value of the disease and nomal tissue were calculated.Using the software Track Vis Version0.5.1(Build2010.03.15) Public to analyze the change of the white matter fiber bundles.Results:MRA can display the occlusion of the left cerebral middle artery and disappearment of the normal vascular signal since30min after infarction, help to determine the model is successful or not.DWI,DCavg map and FA map can display ischemia clearly:the lesion is high sifnal in DWI,low signal in DCavg map and FA map.There was any abnomal signal30min and3h after infartion at T2WI,and began to appear high signal from6h.Infarction volume of DWI at any point,T2WI at6h,9h and12h obviously less than the volume of DCavg(P<0.05). Volume of DWI at6h is more than the volume of T2WI(P<0.05),the volume of DWI and T2WI at9h,12h has no significant difference(P>0.05).DCavg and FA of ROIs of core and margin at disease side and normal side have significant difference.DCavg decreased both core and margin from30min,and their minimum appeared at6h,when it came to9h there were a temper step-up and then decreased slightly at12h,and there was no significant difference between core and margin at9h(P<0.05).FA decreased both core and margin from30min,when it came to9h there were a temper step-up and then decreased slightly at12h,and there was no significant difference between core and margin at6h(P<0.05).DTT shows the white matter fiber bundles reduced,pressed and curly.Conclusions:MRA can display the interruption of the left middle cerebral artery, help to determine the model is successful or not.DWI,DCavg map and FA map can not only diagnose infarction early,but also evaluate the size of the infarction. DWI,DCavg map and FA map can display the size of the infarction and the evolution of the ischemic penumbra.T2WI can show high signal6hours after infarction,meaning irreversible damage.DWI,DCavg map,FA map and T2WI can display the abnormal signal of the infarction aera,but the volume obtained from the DCavg map is close to that obtained from TTC dying.DCavg map can not only display the infarction early and eveluate schemic penumbra existing or not,and can evaluate the infarction volume accurately,so it is the best way. DTT shows the white matter fiber bundles reduced,pressed and curly at the superacute phase of the infarction,and display the process morphologically and functionally.