Stratification of Heterogeneous Diffusion MRI Ischemic Lesion With Kurtosis Imaging Evaluation of Mean Diffusion and Kurtosis MRI Mismatch in an Animal Model of Transient Focal Ischemia

Background and Purpose-Ischemic tissue damage is heterogeneous, resulting in complex patterns in the widely used diffusion-weighted MRI. Our study examined the spatiotemporal characteristics of diffusion kurtosis imaging in an animal model of transient middle cerebral artery occlusion. Methods-Adult male Wistar rats (N = 18) were subjected to 90 minutes middle cerebral artery occlusion. Multiparametric MR images were obtained during middle cerebral artery occlusion and 20 minutes after reperfusion with diffusion-weighted MRI obtained using 8 b-values from 250 to 3000 s/mm(2) in 6 diffusion gradient directions. Diffusion and kurtosis lesions were outlined in shuffled images by 2 investigators independently. T-2 MRI was obtained 24 hours after middle cerebral artery occlusion to evaluate stroke outcome. Results-Mean diffusion lesion (23.5% +/- 8.1%, percentage of the brain slice) was significantly larger than mean kurtosis lesion (13.2% +/- 2.0%) during middle cerebral artery occlusion. Mean diffusion lesion decreased significantly after reperfusion (13.8% +/- 4.3%), whereas mean kurtosis lesion showed little change (13.0% +/- 2.5%) with their lesion size difference being insignificant. Conclusions-We demonstrated that mean diffusion/mean kurtosis mismatch recovered reasonably well on reperfusion, whereas regions with concurrent mean diffusion and mean kurtosis deficits showed poor recovery. Diffusion kurtosis imaging may help stratify heterogeneous diffusion-weighted MRI lesions for enhanced characterization of ischemic tissue injury. (Stroke. 2012; 43: 2252-2254.)