Study on Hyperacute Cerebral Infarction and Reperfusion in Rat with Diffusion Weighted Magnetic Resonance Imaging

Objective To observe the appearance of hyperacute cerebral infarction and reperfusion in rat model after middle cerebral artery occlusion (MCAO) on diffusion weighted imaging and to study the relevant pathologic basis.Materials and Methods Twenty seven Wistar rats were divided into 5 groups: group 1 (n=6), non reperfusion; group 2, 3 and 4 (n=4 for each), reperfusion at 30min, 1h and 2h ofter MCAO, respectively; group 5 (n=9), sacrificed at different intervals after MCAO for histologic and electro microscopic examination. DWI and T 2WI at different intervals were performed in all rats of group 1～4. TTC was done after the last examination. Apparent diffusion coefficient (ADC), relative ADC (rADC) and the area of hyper intensity on DWI and T 2WI were measured.Results DWI demonstrated hyper intensity in the ipsilateral hemisphere at 30min after MCAO in all rats, while T 2WI showed normal. With the lapse of time, DWI signal intensity and the area of hyper intensity increased. ADC and rADC of abnormal areas continuously declined within 6 hours after MCAO. Microscopic changes varied from scattered neural cell necrosis at 30 min to diffuse histologic damages at 24h. After reperfusion, abnormal area recovered entirely or partially in both group 2 and group 3, but no obvious changes were found in the rats of group 4.Conclusion DWI is highly sensitive to hyperacute cerebral infarction, it is very helpful in guiding clinical therapy and in evaluating therapeutic effect.