Diffusion and Perfusion MR Imaging of Acute Cerebral Ischemia with Reperfusion:A Experiment in Rats

Purpose:To assess the value of DWI and PWI in evaluating penumbra of acute cerebral ischemia.Materials and Methods:A total of 40 SD rats were randomly divided into four groups.Group A was sham-operated for control study,Group B,D were occluded for 2,6 hours and reperfused for 2,24 hours respectively.Group C was occluded for 2 hours and reperfused for 24 hours,7 days.DWI,PWI,T1WI,T2WI were performed before and 2,24 hours,7days after reperfusion.ADC,CBV,CBF,MTT topographical maps were reconstructed at the work station.The outcomes of serial MRI were compared with TTC stain and pathological findings.Results:In group A,neither abnormal signal of DWI,PWI nor pathological changes were found.In group B,C,D hyper-intensity signal occurred on DWI in the territory of middle cerebral artery after occlusion.The region of abnormal signal intensity on DWI was larger in group D when compared with group B,which corresponding intracellular edema revealed by electron microscopy.Twenty-four hours after reperfusion,the area of hyper-intensity in DWI was same as that before occlusion in group B and larger in group D.Seven days after reperfusion in group C,DWI showed abnormal in six rats but ADC returned to normal in all the 10 cases.Perfusion deficit maintained on PWI both in group B and D during occlusion,but the area was larger than that of DWI in group B and equal in group D.Conclusion:DWI can detect ischemic lesion sensitively and PWI can monitor hemodynamics change sensitively,so that combined DWI and PWI may define ischemic penumbra.