| Objective : Transient ischemia is one of the most common diseases endangering health seriously with features of high incidence, high disability rate and high relapse rate. Early diagnosis is the premise of early treatment, the purpose of early treatment is to retrieve ischemia penumbra (IP), and to prevent IP from developing into irreversible cerebral infarction. Therefore, identifying IP and understanding its developing process is very significant to guide clinical treatments. Diffusion weighted imaging (DWI), perfusion weighted imaging (PWI) and flow-sensitive alternating inversion recovery (FAIR) provide new methods for IP diagnosis and direct and individual imaging information as well.The study is to find one simple and lasting middle cerebral artery occlusion model in a rabbit. DWI, PWI and FAIR in 24 hours are performed to see whether IP exist or not and its existent time and area, and compare LM, immuno-histochemistry and cerebral pathologic change for studying developing process of IP, so as to provide theoretic basis for making therapeutic schedule, prognosis and judging curative effects. Method : 49 New-Zealand rabbits, male or female, 4-6 months old, weighted 2.5-3.5 kg, provided by Animal Center of Hebei Medical University. The experiment adopted completely randomized design. Rabbits were divided into ischemia-reperfusion group (n=35) and control group (n=14). Each group was divided into seven subgroups of ischemia 30 min and reperfusion 0.5 hour, 1hour, 2hour, 4hour, 6hour, 12hour, 24hour. 5 rabbits in every subgroup of I/R group and 2 rabbits in every subgroup of NC group. All rabbits were bred one week in the animal center after purchasing. And then were fasting for 12 hours but freely drinking water before operation. After being anaesthetised by 2% pentobarbital sodium 1ml/kg (20mg/kg) through slow ear vein injection, the rabbit was fixed on the operation table, remaining respiration free. Cervical part of rabbit was prepared and sterilized. We adopted median incision of cervical part, parted subcutis and muscle layer and then found left common carotid artery, internal carotid artery and external carotid artery. We selected 0.53 mm guide wire and inserted it into middle cerebral artery in order to cause MCAO. After that, the rabbit undertook MRI checking, to confirm model success. Following protocols were used : DWI checking before 15 min ischemia and MRI scanning after 30 min ischemia , 0.5 hour, 1 hour, 2 hour, 4 hour, 6 hour, 12 hour, 24 hour reperfusion. Scanning sequences consist of T1-FLAIR, T2-FLAIR, PROP-T2, DWI, PWI, FAIR. The utilizing of MR imaging, LM immuno-histochemistry can not only observe infarction area, nerve function absence, apparent dispersion coefficient ratio (ADCR), Cytc releasing and caspase-3 protein expressing but also evaluate the value of DWI,PWI and FAIR in IP diagnosis.Results : 1 49 rabbits were taken but 43 rabbits get into results analysis for 6 rabbits missed because of model failure or death. 2 There was no nerve function absence in group NC vs 2.28+-0.47 in I/R group.(p<0.001). 3 In I/R group , abnormality of DWI transienting vanished at the morning of reperfusion but it reappeared after 4-12 hours of reperfusion. On T2WI high signal emerged after 4-6 hours reperfusion. 4 The rADC at the center of focus in control group was normal in NC group. It was transient normal at the morning of reperfusion in I/R group, but it decreased again after 4-24 hours reperfusion. 5 The rADC of perimeter maintained normal level in NC group. But in I/R group , there was no change at 0.5-2 hours and descent in 2-6 hours and increase at 6-24 hours gradually. In comparison with rADC of every time point in center of focus and perimeter, there was no difference at every time point except 0.5 hour, 4 hour ,24 hour, (P<0.05). 6 T2WI signal intensity ratio of infarction area: maintaining normal level in NC group, but in I/R group slowly increasing at 0-4 hours and fast advancing at 4-24 hours. 7 PWI ischemia penumbra chart showed that the area of max-deck mismatch gradually diminished with the time going by. In the ischemia penumbra chart, the blue-marked area at center was infarction area, green-marked area in perimeter was demi-dark band , red-marked area was basi-normal area of reperfusion . NEI chart showed that signal intension was increasing progressively from center part of infarction to perimeter. 8 FAIR demi-dark band chart was coincident with PWI deni-dark band chart. The max-deck mismatch area had statistics significance at every time point (P<0.05) except 0.5 hour (P>0.05)between FAIR and PWI. But the observed area in FAIR was higher than in PWI. 9 LM observation : The neuron morphosis was normal in NC group , but in I/R group intercellular substance and cell was swelling, cellular structure was severely destroyed and some neuron was necrosis . Cytc and caspase-3 protein expressing was small in NC group vs generous at perimeter of reperfusion focus in I/R group (p<0.01).Conclusion : 1 With reperfusion after ischemia 30 min Secondary ischemia damage mainly emerged which showed reappearance of late onset focus at DWI. 2 DWI false color chart was helpful for confirming the existence of IP and its existent time and area. 3 Because the rADC of infarction center was different from rADC of IP , it was possible to infer wether IP exist or not by utilizing rADC. 4 PWI demi-dark band chart could sensitively ascertain IP existence , its existent time and area. 5 FAIR demi-dark band chart was helpful to diagnosize clinically IP existence, and guide treatments and observe effects. But FAIR overestimated IP existence easily. 6 The utilization of Demi-dark band chart was useful in judging patient's conditions directly and then adjusting therapeutic schedule and appraising its effect. 7 Cytc releasing and caspase-3 protein expressing played an important part in perimeter demi-dark band area of brain ischemia-reperfusion. |
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