| Part I : A New Embolism Model of Canine Cerebral InfarctionObjective: The experiment is to establish a new canine model of focal cerebral infarction suitable for the study of medical imaging especially.Method: 10 anaesthetized dogs were selected into the study, among them seven dogs were included in experiment group and another three belonged to sham-operation group. The right femoral artery was punctured in the inguinal region and a catheter was introduced and advanced under DSA fluoroscopic until the tip was in the cavity of internal carotid arteria after passing through aortic arch and abdominal aorta, then cerebral infarction was produced by injection 3-5 polyvinyl alcohol ( PVA) particles with diameter of 800um into internal carotid arteria. The sham-operation group underwent the same process except injection of embolus. The model was evaluated by DSA, MR-PWI and MR-DWI, neurological deficit score and light microscopy after being stained with H&E.Results: The second day after anaesthesia, all experimental dogs showed neurological deficit ranging frommind hemiparesis to death (n=2) and ischemic morphology changes such as swollen of tissue, shrunking of neurons or degeneration of nucleus were observed under light microscopy, . High signal and decreased blood perfusion were observed in four dogs at MCA supplement on MR imaging and the blood vessel in the corresponding area was seen discontinue on DSA. Another three experimental animals showed complicated or independent ischemic lesions on areas outside MCA supplement region. No ischemic lesions could be found via pathological examination and MR imaging in animals of sham-operation group.Conclusion: A reliable canine stroke model with minimal trauma and high survival rate could be produced by this method, which provides an opportunity for medical imaging study and subacute, chronic clinical follow-up study for investigation of therapeutic interventions.Part II: Evaluating the Effectiveness of VEGF Gene Therapy of Canine Brain Infarction by MRI.Objective: Vascular endothelial growth factor (VEGF) is considered to have the ability to expedite angiogenesis and augment collateral vessel formation, which have strong clinical therapeutic potential to stroke patients. In order to impel the clinical study of VEGF, we make an experimental research to evaluate the effectiveness of gene therapy of ischemic infarction model of canine by VEGF plasmid, usingMR-PWI and MR-DWI as a repeatable and unhurt follow-up examination method.Method: 18 adult dogs were included in the experiment and the focal cerebral ischemic infarction model was produced as described in part I of the thesis. Animals were divided into three groups according to the different time of sacrifice: the next day, n=3; the first week, n=7; the second week, n=8. Each group was divided into two subgroups, the experimental group which was given pcD2/hVEGFm plasmid 600 u g by drilling on skull and the control group which was given the same amount of saline in the same way(n=3). The three dogs sacrificed next day all belonged to control group and was given no experimental handle.MR imaging of the 18 dogs was conducted at 1,2,3,4 and 24 hours after thrombosis and was repeated on the 3rd, 7th, and 14th day. The neurology defect score was accessed as Purdy P had done. After various survival time, dogs were sacrificed by intracardiac injection of 2.5% formaldehydum plus 1.5% glutaraldehyde and the perfusion fixed brain was removed by craniectomy, specimens were selected based on the abnormal manifestations on MR images and stained with HE or immunohistochemistry, examined by light microscopy. Other specimens were disposed respectively and observed by electro microscopy. The microbloodvessel count (MVC) and VEGF immunostained cells were calculated after immunohistochemistry staining.Lesion-to-normal tissue signal intensity ratio on ADC maps (ADCr), echo-planar T2-weighted images(T2r), relative CBV(relCBV) and MTT were calculated after MR scan. The evolution rates of infarction... |
