[A study of ischemic penumbra by perfusion and diffusion-weighted imaging at high-field MRI (7.0 T)].

OBJECTIVE: To approach the value of perfusion-weighed and diffusion-weighted imaging at high field intensity (7.0 T) MR in research of the ischemic penumbra in acute cerebral infarction of rats. METHODS: Acute cerebral infarction of rat was induced by occluding middle cerebral artery (MCAO) with suture. Sixty SD rats were divided into six groups randomly of ten including sham operation group, and groups of MCAO for 0.5, 1.5, 3, 6, 24 h. Then all rats were examined by PWI, DWI, T1WI, T2WI and MRA at corresponding time point. Regional cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), mean transit time (MTT) topographical maps were reconstructed and the relative values of rCBV, rCBF, MTT, DWI-derived (rVD) and PWI-derived (rVP) lesion volume were calculated. The outcomes of serial MRI were compared with TTC stain and pathological findings. RESULTS: Neither abnormal signal of MRI nor TTC stain or pathological changes were found in sham operation group. The rCBV, rCBF was significantly decreased but rMTT obviously extended of the area of middle cerebral artery blood-supply of each group of MCAO. The core of infarction was more serious than the edge of infarction. Abnormal signals were found in the MCA-supplying regions in the DWI and PWI of all of the groups of MCAO. The size of rVD became bigger with the time going on but no significant difference of rVP. The size of rVP was larger than rVD before MCAO of 6 h (P < 0.05). There was no significant difference between PWI and DWI after 6 h (P > 0.05) and also between TTC at 24 h and DWI after 3 h (P > 0.05). CONCLUSION: Perfusion-weighed and diffusion-weighted imaging at high field intensity (7.0 T) MR dynamic displaying the existence and the process of ischemic penumbra in acute cerebral infarction of rats provides a basis for further study.