Spatiotemporal characterization of brain infarction by sequential multimodal MR imaging following transient focal ischemia in a Rat model of intra-arterial middle cerebral artery occlusion

Objectives To assess spatiotemporal brain infarction evolu- tion by sequential multimodal magnetic resonance (MR) im- aging in an endovascular model of acute stroke in rats. Materials and methods A microwire was selectively placed in the middle cerebral artery (MCA) in 16 consecutives rats dur- ing 90 minutes occlusion. Longitudinal 7-T MR imaging, in- cluding angiography, diffusion, and perfusion was performed during ischemia, immediately after reperfusion, 3 h and 24 h after subsequent reperfusion. Results MCA occlusion was complete in 75 % and partial in 18.7 %. Hypoperfusion (mean ± SD) was observed in all ani- mals during ischemia (-59 ± 18 % of contralateral hemisphere, area 31±5 mm2). Infarction volume (mean±SD) was 90 ± 64 mm3 during ischemia and 57 ± 67 mm3 at 24 h. Brain infarction was fronto-parietal cortical in five animals (31 %), striatal in four animals (25 %), and cortico-striatal in seven animals (44 %) at 24 h. All rats survived at 24 h. Conclusion This model is suitable to neuroprotection studies because of possible acute and close characterization of spatio- temporal evolution of brain infarction by MR imaging techniques, and evidence of ischemic penumbra, the target of neuroprotection agents. However, optimization of the brain infarct reproducibility needs further technical and neurointerventional tools improvements. Key points • Nitinol microwire is MRI compatible allowing spatiotempo- ral characterization of brain infarction in rats. • Microwire selective placement in middle cerebral artery al- lows complete artery occlusion in 75 %. • A diffusion/perfusion mismatch during arterial occlusion is observed in 77 % of rats.