| Background and objectiveStroke includes two types: intracranial hemorrhage and brain infarction. It is one of the grisly killers of the people's health. And it is one of the most common and dangerous disease with very high mortality & disability rate in alive people. Early detection and diagnosis are the keys to increase the survival rate and decrease the complications of the intracranial hemorrhage (ICH). Following the development of medical imageology, especially the CT and MRI application, early diagnosis became easy and facility and strength assist the earlier treatment. Former viewpoint about the intracranial hemorrhage deemed that the process of the brain hemorrhage was a single vector course, and would stop quickly. But the newer viewpoint considered that this process might be a incessancy process or appear repeated, and those was be approved during the clinical experience. Therefore the repeated clinical symptom observed and assistants examined are obligatory. However, nowadays imaging facility (CT, MRI, TCD et al) only offers incontinuous data, and can not persistent offer the correlative data. During the period of former and latter CT scans, surgeons obtain the accurate clinical data only through the clinical syndromes and heart electricity and breath monitor system. It brings much inconvenient and might affect the treatment in time. Consequently it pressed for a new monitor system that could supply the hemorrhage process in real time in clinical.Electrical bio-impedance is one of the instinctual properties of the organism. Electrical Impedance Tomography (EIT) can provide the variety of the electrical impedance during the pathological process. For EIT technique has the advantages of harmless,low cost, easy to use and functional imaging. Those features make it more fit for long time imaging monitoring. Therefore, in this study, we arrange to image monitoring the intracranial hemorrhage animal model use EIT technique. And try to obtain a new system for monitoring the skull's impedance variation.Material and methodWe place a plaster hemispherical shell into a hemispherical container to simulate the skull layer and filling the container with CaSO4 saturated solution to simulate the scalp and the brain tissues. The resistivity disturbance was made by immersed an agar to simulate the disturbance caused by blood. In animal model experiment, we use animal model with the instrument of EIT to study the resistance changes of the brain in acute ICH. 28 piglets (weight 15 kg) were were deprived of food and water overnight before the experimental procedure. And all the animal were divided into four groups, one group including 4 animals infusing artery blood deprived the skull and scalp;the others group including 8 animals in each one: the second group infusing artery blood, the control groups infusing distilled water and saline separately. After anesthetized successes, a cranial burr hole (1.5 mm) was then drilled 10 mm to the right of the sagittal and 10 mm anterior to the coronal suture. A 7.5-gauge sterile plastic trocar (length 19 mm) was then placed stereotaxically into the center of the frontal cerebral white matter at the level of the caudate nucleus and cemented in place. An infusion pump was then connected, and 5 ml of blood (distilled water or saline) was infused into the brain tissue at a rate of 40μl per second within 3 minutes.16 Ag/AgCl electrodes were placed on the scalp of piglets annularly. The centre of a circle was located on the cross of the joining line of two lateral-canthi and the median line of the head. The semidiameter of the circle was 7-8cm. All of the electrodes were located on the circumference orderly. Before the blood infusing, we monitored the foreground at least for 60 frames. After the blood infusion was finished, we continuously collected the data for at least 30 minutes. After EIT monitor finished, we had an X-ray CT (GE Company) scan to validate the model. At the same time, the volume of the hematoma was calculated according to the CT imaging. All surgical procedures were performed with the use of aseptic techniques. Core temperature was measured with a rectal thermistor probe and was maintained at 38.5±0.5°C with the use of a warm water blanket.ResultThe results in physical model show that the skull handicapped the detection of resistivity disturbance inside cranial greatly. And in animal model expericment, in the group of infusing blood with deprived the skull and scalp, the resisitivity decreased rapidly, and after the stopping the infusing the resistivity increased slowly; in the distilled water, the resisitivity iecreased rapidly, and after the stopping the infusing the resistivity decreased slowly. In the saline group, the resisitivity decreased rapidly, and after the stopping the infusing the resistivity increased slowly.In exam group, the region of hematoma can represent clearly higher impedance variation. And during infusing blood, the resisitivity increased rapidly, and after a little decreasing the resistivity increased slowly.ConclusionAlthough the configuration of human head is so complex which limited the application of EIT on the head, it could obtain the definition imaging by polar driver pattern. In the forepart of the ICH, resistivity configuration increased at the region of the hematoma, and the resistivity configuration of the whole head increased too. The mechanism of the resistivity variation might be related with the cerebral-spinal fluid shifting to the further region following the intracranial pressure increasing. Although the detail of the changing rule is still not clear, it might have a widely application in early diagnosis and assistant treatment in clinical. |
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