MR Image Technology Evaluation Of The Protective Function Of NO Precursor/Donator On Cerebral Ischemia Injury By Interventional Therapy

Objective: To establish a rat model of middle cerebral artery occlusion(MCAO) by the blockage or obstruction of middle cerebral artery(MCA). NO precursor L-Arginine(ARG) and NO donator Nitroglycerine(NG) are administrated by interventional therapy. T1-weighted imaging(T1WI), T2-weighted imaging(T2WI), Diffusion weighted imaging(DWI) and Perfusion weighed imaging(PWI) are applied to evaluate blood circulation and brain injury of the effected brain region to elucidate the protective function of ARG and NG in the early stage of brain damage.Methods: The MCA was occluded by insertion of a suture through the internal carotid artery(ICA) of SD male rats to duplicate ischemia-reperfusion model. Reperfusion was established by suture withdrawal. After 2h of blockage, reperfuse and administrate ARG(0.12ml/kg), NG(0.06ml/kg) by interventional therapy through the ICA simultaneously. Imageology indexes such as T1WI, T2WI, DWI, PWI are utilized to assess the changes in 2 hours after ischemia, 3 hours after reperfusion and 24 hours after reperfusion, respectively. Compare the results by Longa score, TTC stain and pathological observation.Results:(1) Statistic significance(p<0.025) has been seen between drugs groups and MCAO group in 3 hours after ischemia-reperfusion by Longa score. Motor function of animal models has restored after 24 hours and differences between groups disappear.(2) Obvious decrease of DWI high signal region and TTC pale region in drugs groups manifests significant difference with MCAO group.(3) The value of Apparent Diffusion Coefficient(ADC) and relative ApparentDiffusion Coefficient(rADC) in caudate putamen(CP) region increase gradually from 2 hours after ischemia to 24 hours after reperfusion in each group. More obvious increase can be seen in drugs groups than MCAO group. ADC, rADC value in CP region of the drugs groups have manifested significant difference(p<0.01) from MCAO group.(4) We can see directly from ADC shape in 3 hours after reperfusion, focus of injury which locates in caudate nucleus and dorsal caudate putamen, part of which spreads to neighbor subcortex, is the smallest in ARG group. The affected area is even bigger in GBE group and spreads to parietal lobe and temporal lobe cortex. The affected area, which is the biggest, is the tributary area of MCA in MCAO group.(5) Intensity-time curve tells the signs of ischemia-reperfusion induced brain injury and recirculation. PWI intensity-time curve shows descending amplitude of peak value in 2 hours after ischemia has diminished, and the curve manifests more decrease in descending amplitude of peak value, which indicates successful reperfusion in 3 hours after reperfusion.(6) MCAO group lost large sums of neurons in caudate putamen(CP) region. The loss of neurons can also be seen in drugs groups with different degrees.(7) Positive correlation(r=0.67, p<0.05) exists between infarction area in 3 hours after reperfusion and Longa score, which shows negative correlation(r=-0.75, p<0.05) with rADC value.(8) No statistic difference can be seen in blood pressure decrease between drugs groups and control group.Conclusion:(1) Interventional therapy with NO precursor/donator has showed significant protective function in the early stage of brain ischemia and avoid the severe side effects accompanied with the blood pressure plummet.(2) DWI, ADC and PWI intensity-time curve provide the precise neuroradiological indexes to help further explore the protective mechanism.