Experimental Study Of Electrical Impedance Tomography On Early Cerebral Ischemia Monitoring

Background:Ischemic cerebrovascular disease seriously influences human beings'health and shows detrimental effects on people, family and society for its high incidence and morbidity. Up to now, our knowledge of its physiopathology is still incomplete, and a secure and effective method for real time dynamic monitoring is insufficient. In recent years, electrical impedance tomography(EIT) becomes a popular technique studied by different countries. EIT is a new imaging technique that targets the internal electric impedance distribution and variance as image forming objective; its merits include functional imaging and dynamic image monitoring. Our study aims to establish an animal model of cerebral ischemia and apply the EIT technique on monitoring the early process of cerebral ischemia, in order to discuss its change pattern and value in clinical application. Methods:(1) 30 rabbits; make a skull hole (d = 5 mm) in with outer plate and diploe removed, only inner plate maintained; inject photosensitive agent from the ear-edge vein and cast light from the LG-150B cold light source onto the skull hole for 30 min; observe and evaluate the clinical performance caused by neurological impairments after 24 h of model establishment; put the rabbits to death after 48 h and obtain the brain to make regular pathological section; (2) 6 rabbits; the focal cortex ischemia model was established by photochemical method and the whole dynamic process was monitored by electrical impedance tomography system for 90 min; 2 of the model rabbits were put to death immediately after monitoring and their illuminated area of brain tissue were separated for electron microscope observation; illuminated area of brain tissue in other 4 model rabbits separated for regular pathological section; (3) 10 rabbits; One internal carotid artery were separated and exposed in order to ligate for 10 minutes; the whole process of reversible occlusion of internal carotid artery was monitored by the electrical impedance tomography system.Results:(1) Successful reproducible rate of the model is 96.3%. Pathological analysis shows that typical cerebral infarction was observed with lamellar necrotic tissue; (2) The cerebral electrical impedance tomography system successfully monitored distinctive image of cortical spreading depression occurred in the early rabbit cerebral cortical infraction induced by photochemical method; (3) The cerebral electrical impedance tomography system showed that the resistivity of the target brain area which was supplied by the occluded internal carotid artery increased persistently during the reversible occlusion. After reconstruction of cerebral blood flow, the resistivity of the target area fell a little, but did not reach incipient level.Conclusion:The animal model of focal cerebral cortical infarction in rabbit induced by photochemical method without craniectomy is conveniently established and proved to be valid. It caused less injury to the test animals so that the inner skull environment is comparably stable, which makes a much better representative model for real cerebral infarction situation. Cerebral electrical impedance tomography system could monitor distinctive image occurred in different types of early cerebral ischemia and has orientating function on ischemic area, which showed its potential value in clinical treatment.