| Background and purpose: Cerebral infarction was a universal brain vessel disease which had a significant morbility, deformity and mortality. In order to increase survival rate and to decrease deformity and mortality, it was important to diagnose and treat this disease earlier. MR diffusion weighted imaging (DWI) and perfusion weighted imaging (PWI) sequence provided a new method to early diagnose cerebral infarction. After infarction, the water diffusion in focal ischemic brain tissue was limited. By measuring the changing of Brown movement of the water, DWI can detect changes of signal intensity within 5 minutes after the occurrence of ischemia, and decrease of the apparent diffusion coefficient (ADC). The lesion showed high signal intensity on DWI and dark area on ADC mapping. By using echo planar imaging sequence to perform susceptibility contrast agent PWI which can alter the magnetic ratio of the focal tissue and MR signal intensity, hence it can evaluate the state of the hemodynamics of brain tissue noninvasively and the activity of the focal brain tissue. PWI was an important functional imaging technique. After ischemia, the signal intensity of normal brain tissue decreased very fast because its speed of blood flow was faster than the abnormal brain tissue, whose signal intensity did not decrease or did not decrease obviously, therefore the ischemic brain tissue showed relatively high signal intensity, which suggested abnormal hypoperfusion area. With the combination of these two techniques, MRI can assess the position and the area of theischemia, and may detect ischemic penumbra (IP). The purpose of our research was to establish an easy and stable middle cerebral artery occlusion model (MCAO) in rabbit, using DWI and PWI sequence study the model within 24 hours. We may evaluate thediagnostic value of the cerebral infarction in vivo, and compare with pathomorphology to provide theoretical foundation of diagnosing acute ischemia by using DWI and PWI.Objects and methods: 44 New Zealand rabbits regardless of male or female were randomized into two groups, 36 rabbits were included in the experimental group and 8 rabbits were classified as control group. For the experimental group, a transobital electrocoagulation was carried out to occlude the middle cerebral artery, whereas control group only exposed the middle cerebral artery, but no electrocoagulation was performed.After MCAO, the rabbits of experimental group and control group were examined by MR scanner in 0.5h, Ih, 2h, 4h, 6h, 8h, 12h and 24h. The scan sequences included SE sequence TjWI, T2WI, FLAIR sequence, DWI and PWI. Specimens of the brain tissue which were obtained correspondently to MRI scan were observed by microscopy and electrical microscopy. The two Specimens of the brain tissue which were obtained correspondently to MRI scan were stained by TTC. The experimental group animals were examined by blood biochemistry to show the changes of PO2, PCC>2, PH, plasma glucose and ractal temperature before and after MCAO 4h, 8h, 12h and 24h.All of the MR images were processed in the work station and ADC, rADC values and changes of the infarction volume were measured according to MR DWI and PWI. The statistical analysis was executed by SPSS 10.0 software, statistical methods were t-test and analysis of variance.Results: 1. After MCAO, the position of the infarction was mostly located in the basal ganglia, hippocampal and cortical areas. 2. The value of ADC began to decreased in 0.5h (lesion6.41+0.72x104mm2/s, control 8.80+47x104mm2/s, t=924, P<0.05), rADC value was 0.6 1+0.07, and decreased to foe lowest in 8h (lesion 4.73+0.51 x104mm2/s, control 8.81i0.60xl04mm2/s, 1=12,05, p<0.05), rADC value was 0.56HX05, and returned in 24h (lesion 6.17+0.45xl04mm2/s, cortral 922+027x104mm2/s, t=3.01, p<0.05), rADC value was 0.64+0.06. 3. The infarction volume showed abnormal high signal intensity on DWI and hypoperfusion on PWI, whereas the hypoperfusion areamostly showed larger than the abnormal high signal intensity area, as sugge...
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