Rat cerebral ischemia induced with photochemical occlusion of proximal middle cerebral artery: a stroke model for MR imaging research.

A stroke model in rats with photochemically induced thrombosis (PIT) of proximal cerebral middle artery (MCA) is introduced for magnetic resonance imaging (MRI) study. Thirty-seven rats subjected to surgical and optical procedures for inducing the PIT models were scanned using a 1.5-T scanner with T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI), and contrast-enhanced perfusion-weighted imaging (PWI) at 1 h and 24 h after MCA occlusion. The penumbra evolution and PWI-derived parameters including relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) were monitored; and the relative lesion size (RLS) was compared with the final RLS on the gold standard triphenyl tetrazolium chloride (TTC) staining at 24 h. The results showed that the focal cerebral ischemic lesions were detectable in all rats with different MR approaches. The lesion on PWI at 1 h and on all MR images at 24 h was matched well with that seen on TTC staining; the peri-infarct area decreased from 6.2 +/- 7.2% of the brain volume at 1 h to 0.3 +/- 5.6% at 24 h. Compared to that in the contralateral hemisphere, rCBV in ischemic region was 52.6 +/- 21.4 and 40.0 +/- 15.8% (p > 0.05), and rCBF was 64.6 +/- 11.2 and 47.3 +/- 11.1% (p < 0.05) at 1 h and 24 h respectively. The present PIT model in rats has been successfully adopted for MRI research, which might be feasible for certain stroke studies and should be beneficial for the evaluation on effects of potential diagnostic and therapeutic approaches.