An Experimental Study On Cerebral Hemodynamics And Ischemia Penumbra In Rabbits By Multislice CT Perfusion Imaging

IntroductionTraditional CT perfusion imaging in the past was limited by single section. Multi — slice CT combined with dynamic perfusion imaging extended the domain of Z axle, which could obtain the perfusion parameter of different sections in once perfusion imaging, making the evaluation of the lession more objective and accurate. Multislice spiral CT imaging has a rapid, high spatial resolution and scanning larger domain method, but little is known about which is used in cerebral hemodynamics, especially in the study of animal experiment. So we present the use of a noninvasive CTPI method in animals for the study of hemodynamics, which can lay a good foundation to the CTPI of human brain ischemia and brain tumors.It is important to establish a reliable and repreduciable brain ischemia animal model to study physiopathologic mechanism and prevention and cure of human brain stroke. The domain of MCA is the predilection site of humain brain stroke, so MCAO model is considered the standard animal model of regional brain ischemia. The method of thread embolism that create regional MCAO brain ischemia model has been used in the mouse widespread, whereas the rate of success and the stability are both low when it was used to establish rabbits brain ischemia models.There is a low perfusion ischemia - penumbra between ischemia core and normal brain tissue after regional ischemia, which can be rescued by recovering blood or medicine intervention. Rescuing ischemia penumbra is the nuclear assignment of thrombolytic therapy. It is very important to judge brain ischemiapenumbra to evaluate brain hemodynamics accurately and determine infarction brain tissue correctly with CTPI.Judging ischemia penumbra with CTPI is in the study phase now. There is no reports about the hemodynamics parametres and dynamic change of ischemia penumbra and infarction in the domestic reports. At present, there is no general conclusions although some scholar aboard have explored.This research topic is about the problems of CTPI study. We analysed normal rabbits brain hemodynamics with MSCT, explore the technique of MSCTPI, established stable and reproducible rabbits MCAO models by interventional ways and judged brain ischemia penumbra preliminary with MSCTPI.Materials and MethodsThe study of brain hemodynamics in healthy New Zealand rabbits by multisection spiral CT perfusion imaging15 healthy New Zealand rabbits were used to perform the perfusion spiral CT scans. Centrifugate and puncture the reagents'femoral vein, then routine scaned the regents, choosed the section of optic chiasma as the central section of perfusion scans, at the same time bolus injected the contrast medium into the ear vein and femoral vein respectively at the rate of lml/s, 0. 5ml/s, and 0. 3ml/s. scans begined 25 minutes after the start of scanning. Then data were processed with perfusion software, including automatic definition of the image threshold, choosing the layers of which the basilar artery and superior saggital sinus were perfectly obtained as the comparited layer; choosing the basial artery as the input artery, and superior saggital as the output vein. After processing the data, we can obtain 8 continuous sections blood functional perfusion maps of cerebral blood flow ( CBF) , cerebral blood volume ( CBV ) and mean transmit time (MTT). Choose the region of interest ( ROI) in the functional perfusion maps and determined the values of the perfusion parameters, then process the data with SPSS12 statistical software. The data was demonstrated with averages add or plus standard deviations, the comparison of the groups was performed using a tow - tailed t - test and analysis of variance, p <0. 05 presented a statisticallysignificant result.To make the model of the acute middle cerebral artery occlusion by interventional waysChoose 24 healthy New Zealand rabbits, 19 of those were operated and 5 of those were not performed complete operation which will be the contrast team. The process of operation included: exposed the two - side femoral vein and artery, centrifugate the left femoral vein and artery, puncture the vein with tro-char, then centrifugate the right femoral artery. With the help of x - ray, seldingers centesis was adopted to puncture the femoral artery, and 3F SP catheter was used to catheterice right carotid artery, then at the branches of that process angiography, so that we can learn the anatomy and make sure where the middle cerebral artery was, then cathetize the start of right internal carotid arteries and send the super smooth micro - catheter to the start of middle cerebral artery , record the length of catheter in the head routine images. The contrast team wasnt send the super smooth micro - catheter into the imternal cartid arteries and middle cerebral arteries. We can obtain 3 groups along with different ische-mic time; 2hous, 4hous and 6hous, then kill the rabbits by injecting overdose pentobarbital. The brain slice were processed by TTC staining method, was fixed by 10% formaleehyde solution to make the paraffin wax slice and was fixed by 2% Glutaral solution to make electron microscope specimenThe experimental study of the judgement of cerebral ischemia penumbra with multi - slice spiral CTThe rabbits MCAO infarct models were performed dynamic scans with multi - slice spiral CT. After unenhanced CT scans of the whole brain to decide the perfusion sections, MSCTPI scans was performed in 2cm domain with selecting eight adjacent 2.5- mm - thick sections centring at the level of the optic chi-asm. CT perfusion data was analyzed at an imaging workstation equipped with cerebral perfusion software. The maps of CBF, CBV and MTT of the rabbits brain were obtained after computing. We cut the heads of the rabbits and took off the brains after scanning, and the brain sections were performed TTC staining to decide the infarction tissue. We selected the section of optic chiasm to preparate paraffin sections with 10% formalin fixation, followed by immunohisto-chemical examination with heat shock protin HSP - 70 and Bel - 2 as first antibody. We selected ROI in the perfusion maps to decide the cerebral ischemia penumbra, and analyzed the hemodynamic parameter values changes in the hy-peracute brain ischemia and the hemodynamic characteristic of ischemia penumbra , analysis expression of HSP - 70 and Bel - 2 in each group, so that we can make sure whether the penumbra appeared or not.ResultsMultislice spiral CT perfusion in Healthy rabbits1. Scan range: 8 continuous sections were obtained in one time scan, those sections can cover most brain from frontal lobe to brain stem. The color of perfusion images is symmetrical, and there were no abnormal perfusion defect.2. The images of the group that was injected by the way of ear vein is defected . However, we got satisfactory images of the other group that were injected into femoral vein.3. There was no statistically significant result (p >0.05) between the parameters of rabbit hemodynamics obtained by injecting contrast medium into the femoral veins at different rates.Establishing a model of MCAO by intervention^ ways1. It was presented that the outernal carotid artery system of rabbits was developed, 7of 19 rabbits has occipital artery, 3of 19 rabbits'middle cerebral artery was supplied by two branches. Two anterior cerebral artery confluensed into each other with no frontal communicating branches, the basilar artery and posterior cerebral artery were more developed in the angiography, and the vertebral basilar system was displayed limpidly in the internal carotid artery angiography.2. There was greater resistance after the micro - filiaments reached middle cerebral artery. The length can arrive at 5.5cm 0.6cm from the start of internal carotid artery to the middle cerebral artery. The experimental group induded 19 rabbits, and 2 of them didnt permit minute guide wire to enter the carotid foramen , otherwise, 2 of them died of carotid artery angiography, the else were a-live well.3. TTC staining showed that ischemiaed for 2 hours had not staining defect, and the staining of 2 rabbits (total 5 ) is white in the area supplied by middle cerebral artery in group ischemiaed for 4 hours. Meanwhile, for the group that ischemiaed for 6 hours there were no exception, all of the 5 rabbits appeared infarction , which is stained pale defection, and wider than the former.4. Pnenomina of the changes in the period of hyperacute ischemia obtained by light microscope and electron microscope showed that in the first group cell endochylema rarefacted, nucleus anachromasis, the rough place of mitochondrion disappered, rough endoplasmic retiaulum degranulated; the second group: tigroid body vanished, neuroglia cells tumefacted, neure cells and heterochro-matin recreased, rough endoplasmic reticulum degranulated, part of mitochondrion became into vacuole; the third group: endochylema puffed into mesh, neure nucleus dissolved, heterochromatin in the nucleus was collected and hy-perplasy, oranelles decreased, mitochondrion became into vacule, blood - brain barrier was destructed.The study to research the range of penumbra and whether the penumbra appear or not in CT perfusion maps1. In the first group, CT perfusion functional maps displayed clear ische-mic area. The domain of color perfusion damage of the maps of CBF and MIT was identical with the tissue blood supplied with MCA. We found the blood low perfusion changed like stepladder, in which the core of ischemia had the lowest perfusion and higher gradually to periphery. The map of CBV showed few changes and TTC staining showed normal or and had not stain damages. In the group of ischemia for 4 hours, the perfusion damages of the maps of CBF and MTT were more obvious and some could be found small non - perfusion domain, some could be found reduced CBV but the domain was smaller than CBF and MTT. The TTC staining of the rabbits brain with CBV descend was damaged. In the group of ischemia for 6 hours, the map of CBF showed serious perfusion damage in which we could found plaque non - perfusion domain in the domain MCA blood supply. The map of MTT was the same as the map of CBF. The damaged domain was more extend in CBV, and the domain was identical with CBF and MTT. The results of TTC staining showed that the domain of MCA blood supply...