Experimental Study On Quantitative Detection And Type Distinction Of Cerebral Edema Based On The Magnetic Induction Phase Shift

Cerebral edema is a fatal pathological condition secondary to traumatic brain injury(TBI)and Cerebral Stroke(CS).After the occurrence of cerebral edema,the excessive accumulation of extracellular fluid causes an increase of in intracranial pressure,which leads to damage to nerve function and even death.Therefore,real-time monitoring of cerebral edema has a positive effect on the treatment and prognosis of patients with TBI and CS.In clinical practice,the most commonly used method for cerebral edema monitoring are imaging methods and invasive ICP monitoring.Imaging equipment such as CT and MRI obtain image data whereas these machines are bulky and have low time resolution which may delay the timing of treatment.However,invasive ICP monitoring has the risk of infection and bleeding,and is likely to cause secondary trauma to patients.The magnetic induction phase shift(MIPS)method focuses on the electrical properties of biological tissues,which has advantages of non-invasive,non-contact,high time resolution.By applying an excitation signal of a certain frequency,the main magnetic field generated by the signal to induce an induced magnetic field in the measured object.Consequently,the induced magnetic field is related to the electrical conductivity of the measured object,and changes in electrical conductivity can reflect the pathophysiological changes of biological tissues.In this study,two cerebral edema models were established to simulate the secondary cerebral edema after TBI and CS,separately.Then,we built a cerebral edema detection system based on MIPS technology to conduct the 24-hour real-time continuous monitoring experiments,through which we explored the feasibility of MIPS method for the quantitative detection and type distinction of cerebral edema.The main research work is as follows:(1)Study on the relationship between MIPS and pathological indexes of cerebral edema(ICP and BWC).In order to further investigate the relationship between MIPS and pathological changes of cerebral edema,this study explored the feasibility of using MIPS method for quantitative detection of cerebral edema.Based on MIPS method,we built an experimental platform for the single-channel detection of cerebral edema,which can realize non-invasive,non-contact and real-time continuous monitoring.In this study,we conducted a24-hour synchronous monitoring experiment on MIPS and ICP in rabbits with whole cerebral edema induced by epidural freezing.In the parallel experiment,the Brain Water Content(BWC)was measured by dry and wet weight measurement.Based on our previous researches,this study conducted in-depth data analysis and established the relationship model between MIPS and common pathological indicators(BWC and ICP).Based on the ICP data and the compensation mechanism,the entire 24-hour experimental process was divided into:compensation period(0-6h),decompensation period(6-18h),and terminal period(18-24h).Combined with the theory of relationship analysis,we studied the relationship between the MIPS and BWC through correlation analysis and fitting method,as well as the relationship between the MIPS and ICP.(2)The establishment of MIPS dual-channel synchronous detection system.A dual-channel synchronous detection system was established for the focal cerebral edema in rabbits induced by ischemia.Due to the slight induced magnetic field and phase shift caused by focal edema lesions,it was necessary to improve the detection sensitivity of the monitoring system.Therefore,we carried out dual-channel synchronous detection of the left and right cerebral hemispheres in rabbits.The system had one excitation port and two detection ports.The phase shift of normal brain hemisphere was used as reference to the phase shift of ischemic brain hemisphere,which eliminated the interference of induced magnetic field in normal tissues,thereby improving the detection sensitivity.(3)The experimental study on MIPS continuous monitoring of focal cerebral edema in rabbits induced by ischemia.Cerebral edema secondary to ischemic stroke is dominated by cytotoxic edema in the early stage and dominated by vasogenic edema in the later stage.This model is suitable for studying the feasibility of type distinction of cerebral edema by MIPS.Differentiating different types of cerebral edema can guide clinicians to implement symptomatic treatment.In order to study the feasibility of MIPS technology for the identification of cerebral edema types,a non-invasive,non-contact,real-time continuous dual-channel synchronous monitoring system was built based on MIPS method.15 rabbits were enrolled in the 24-h MIPS monitoring experiment(10 in the experimental group and 5 in the control group).The thrombin induction method,which conformed to the clinical pathological development process of ischemic stroke,was used to construct an acute focal cerebral ischemia model of rabbits.Brain tissues were taken from seven rabbits for 2%triphenyl tetrazolium chloride staining for verification of the animal model.A symmetric cancellation-type magnetic induction sensor was used to improve the sensitivity and antijamming capability of phase detection.The nonparametric independent-sample rank sum test showed significant differences(p < 0.05)between the MIPS data in experimental group and the control group.Results showed that the MIPS presented a declining trend at first and then an increasing trend in the experimental group,which may reflect the pathological development process of cerebral ischemic stroke.Moreover,TTC staining results showed that the focal cerebral infarction area increased with time.Based on the above research work,the following conclusions are drawn:1.By the study of the relationship between MIPS and BWC,as well as the relationship between MIPS and ICP,we realized the goal of non-invasive,non-contact and real-time quantitative detection of cerebral edema,which laid a foundation for the next clinical experiment.2.The experimental platform for dual-channel synchronous monitoring of cerebral edema based on MIPS in this paper can perform 24-hour real-time continuous monitoring in a wide frequency band,and its data collection,storage speed and phase accuracy meet the requirements of the experiment.3.Our experimental research shows that the application of MIPS method to real-time monitoring of ischemia-induced focal cerebral edema is feasible and has the potential to distinguish cytotoxic edema and vasogenic edema caused by cerebral ischemia.