| Objective to explore the way of identify the size and evolving process of reversible damaged region (RDR) and irreversible damaged region (IDR). Methods Focal iscemia was produced in 35 rabbits by transorbital ligation of left middle cerebral artery (MCA), compared with a sham-operated group of 5 rabbits. The rabbits received magnetic resonance examination of T2-weighted imaging (T2WI), diffusion weighted imaging (DWI) and perfusion weighted imaging (PWI). The evolution of the ischemic lesion was monitored at 0.5, 1, 3, 6, 9, 12, 48 hours after the onset. After decapitation,TTC staining was performed on the rabbits′brainslices.Using paired-T test to analyze the data acquired. Results DWI could identify definite IDR and PWI could identify the ischemic region within 30 min of onset, while T2WI couldn't manifest either until 3 hours. From 30 min to 9 hours, IDR expanded while RDR decreased with continuation. The apparent diffusion coefficient ratio (rADC) presented statistic significance between RDR(0.73±0.07) and IDR(0.53±0.07) (P<0.01).The rrCBV(0.29±0.16) and rrCBF(0.22±0.09) in IDR decreased sharply compared with those of the RDR(0.72±0.08,0.60±0.08 respectively) (p<0.01). The abnormal demonstrated by DWI/PWI showed no significant difference with TTC staining results, except for the 30 min after onset(P>0.05).Conclusions (1) IDR expanded while RDR decreased with time after MCAO. (2) rADC, rrCBV and rrCBF could be used to identify the IDR/RDR.(3) DWI/PWI was a reliable way to identify IDR/RDR. (4) The time window for neuroprotection and thromlytic therapy was 9 hours.
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