Evolution of hyperacute stroke over 6 hours using serial MR perfusion and diffusion maps

Purpose: To develop an appropriate method to evaluate the time-course of diffusion and perfusion changes in a clinically relevant animal model of ischemic stroke and to examine lesion progression on MR images. An exploration of acute stroke infarct expansion was performed in this study by using a new methodology for developing time-to-infarct maps based on the time at which each voxel becomes infarcted. This enabled definition of homogeneous regions from the heterogeneous stroke infarct. Materials and Methods: Time-to-infarct maps were developed based on apparent diffusion coefficient (ADC) changes. These maps were validated and then applied to blood flow and time-to-peak maps to examine perfusion changes. Results: ADC stroke infarct showed different evolution patterns depending on the time at which that region of tissue infarcted. Applying the time-to-infarct maps to the perfusion maps showed localized perfusion evolution characteristics. In some regions, perfusion was immediately affected and showed little change over the experiment; however, in some regions perfusion changes were more dynamic. Conclusion: Results were consistent with the diffusionperfusion mismatch hypothesis. In addition, characteristics of collateral recruitment were identified, which has interesting stroke pathophysiology and treatment implications