Experiential Study Of Perfusion Imaging Using Arterial Spin Labeling In Dynamic Evaluation Of Acute Cerebral Infarction In Rabbits

Objective To assess the value of arterial spin labeling(ASL)and magnetic resonance multi-sequence in dynamic evaluation of acute cerebral infarction.Methods Ischemic cerebral infarction was induced in 42 New Zealand White rabbits by embolizing the middle cerebral artery using autologous clot emboli.7 groups of rabbits were studied.In group 0,ADC and CBF thresholds were established.Routine MR imaging and ASL perfusion imaging were performed 6h before occlusion and at lh,3h,4.5h,6h,7.5h,12h after that.After the scan at each time point after occlusion,the brain was removed,cut and stained with 2,3,5-triphenyltetrazolium chloride(TTC)to evaluate lesion volumes.The abnormal ADC and CBF thresholds derived by group 0 were applied to evaluate lesion volumes of the abnormal signal on the DWI and ASL at each time point in group 1 to 6.Statistical analysis,such as Student’s t tests,repeated-measures analysis and linear-regression analysis,was performed to analyze the TTC-,ADC-and CBF-defined lesion volumes.Results 1 hour after occlusion,the abnormal signal could be observed on both the DWI and the ASL,mainly at cerebral cortex.As the time went on,the abnormal signal became apparent,ADC-and CBF-defined volumes increased and were relatively stable.And CBF-defined lesion volumes were found larger than ADC-defined’s early after occlusion.In group 0,ADC and CBF thresholds of abnormality were derived by adjusting the respective threshold values so that the ADC-and CBF-derived lesion volumes at 3 hours were equal to the TTC-infarct volume at 12 hours,while compared with the corresponding part before occlusion,the thresholds were 0.575±0.02 and 0.437±0.08,respectively.These thresholds were applied to evaluate lesion volumes,ADC-and CBF-defined lesion volumes.There was no statistical difference between The CBF-and TTC-defined lesion volumes at each time point for all 6 groups(P>0.05).In group 6,the CBF-defined lesion volumes were larger than ADC-defined’s at early 1h,3h,4.5h after occlusion,while no significant difference was detected at the next 3 time points;the CBF-defined lesion volumes had statistical differences at all time points,but not any closed two of them.Similar to the former,the ADC-defined lesion volumes kept increased at early 1h,3h in group 6.Conclusion The ASL can sensitively reveal cerebral perfusion impairments for hyperacute cerebral infarction in permanent MCAO model in rabbits by displaying abnormal signals and quantifying the the ischemic lesions.With the use of quantitative perfusion and diffusion imaging,CBF and ADC abnormal thresholds help in mapping three different clusters,cerebral infarction,ischemic penumbra and normal tissue,making it possible to evaluate the spatiotemporal ischemic progression in a living animal.The approach demonstrated useful for monitoring the dynamic changes in cluster membership as a function of therapeutic intervention.