Measurement And Imaging Of Blood Flow Impedance In Functional Areas Of Cerebral Cortex

The detection of physiological states in cortical functional regions is of great importance for brain science research.Cortical blood flow regulation plays a key role in the measurement objects of the existing brain function detection methods.Cortical blood flow regulation plays a key role in changes in hemoglobin concentration.However,efficient methods to detect this process are still lacking.Therefore,the detection and imaging of cerebral cortex blood flow regulation is of great research value.Based on the electromagnetic characteristics associated with the cortical blood flow regulation process,this dissertation utilizes the advantages of bioimpedance technology in continuity and spatial distribution.A new method for detecting and imaging cerebral cortical blood flow impedance based on bioimpedance technology is proposed.This method can be used to detect and image the distribution of cerebral blood flow regulation.In this dissertation,the impedance measurement of cerebral blood flow regulation was studied.The simulation model of cerebral blood flow impedance was designed according to the brain structure,and the dynamic simulation calculation of cerebral cortex blood flow impedance was performed.Meanwhile,a cerebral flow impedance detection system has been studied and designed to obtain multi-channel synchronous signals of cerebral flow impedance.The method of cerebral blood flow impedance image reconstruction is studied to realize the image reconstruction of cerebral cortex blood flow regulation distribution.Finally,an experiment on blood flow impedance detection in cortical functional regions is designed to validate the proposed detection and imaging methods.The main content and innovation points of this dissertation are summarized as follows:(1)For the problem of detecting bioimpedance in cerebral cortical blood flow regulation,a new method for detecting cerebral blood flow regulation based on impedance differential phase shift is proposed.A correspondence between cerebral vascular compliance and vascular volume changes has been established based on the control of blood vessels by the nervous system in cerebral cortex blood flow regulation.The purpose of detecting blood flow regulation in functional regions of the cerebral cortex is achieved by analyzing the information of the blood flow impedance associated with the regulation of vascular compliance under the control of the nervous system.The differential phase shift of the impedance was 10.32-37.6% and 11.18-36.86% in the frontal and posterior brain regions,respectively.The results show that the proposed method is able to measure the blood flow regulation in cortical functional regions of the brain.It provides a foundation for subsequent studies of imaging detection systems and imaging methods.(2)For the dynamic simulation calculation problem of cerebral cortex functional area,a dynamic simulation model of blood flow impedance with cerebral cortex structure was designed based on the real brain structure.Compared with the traditional brain impedance simulation model,this model can simulate the dynamic impedance of cerebral blood flow regulation under the condition of blood supply.In the dynamical simulation study of cerebral cortex blood flow impedance,the electrical parameters of the cerebral cortex region are set to mimic the dynamic changes of the impedance during the blood flow regulation process.Finite element calculations of the electromagnetic field were performed to obtain simulation data for the continuum impedance of the brain model surface.Finally,the model is used to model the blood flow regulation impedance of each cerebral cortex region.Simulation results validate the sensitivity and differences of the brain surface impedance to blood flow regulation processes in different cortical regions.(3)In the process of studying the blood flow impedance detection system in functional regions of the cerebral cortex.In order to solve the problem of synchronous detection of cerebral blood flow impedance signals,a multi-channel synchronous detection system for cerebral blood flow impedance based on detection technology was designed.The system is based on the basic principles of bioimpedance detection.Combined with the characteristics of the electrode array distribution in dynamical simulations of cerebral blood flow impedance.The excitation source,amplification,detection and acquisition modules are designed to address the problem of high sampling frequency in multi-channel synchronous detection of cerebral blood flow impedance.The control software for cerebral cortex blood flow impedance data acquisition has been designed.A complete multi-channel cerebral impedance acquisition system is constructed by integrating various functional modules.The impedance detection performance of the system was tested.The accuracy and reliability of the system function module in impedance measurement was verified.Also,the frequency stability and multi-channel detection accuracy of the system are tested.The test results show that the system can achieve multi-channel synchronous measurements of cerebral cortex blood flow impedance.(4)In the process of studying the reconstruction of the distribution of blood flow regulation in cortical functional regions.The image reconstruction algorithm of cerebral blood flow regulation distribution based on impedance differential phase shift is studied.This algorithm solves the problem of imaging the distribution of cerebral blood flow regulation by impedance differential phase shift.To address the ill-posedness in image reconstruction,an image reconstruction method based on Tikhonov regularization is proposed.To verify the reliability of this approach,simulation experiments of blood flow regulation imaging in different cerebral cortex regions were designed.In this experiment,computed data from a dynamic simulation model of cerebral blood flow impedance are used for image reconstruction.The relative localization error is used to evaluate the localization accuracy of the reconstructed images.Simulation results show that the image reconstruction algorithm used in this dissertation can accurately image the distribution of blood flow regulation.Finally,to verify the feasibility of the proposed blood flow impedance detection and imaging method,a blood flow impedance detection experiment was designed in the cerebral cortex functional region.Neural regulation of blood flow in brain functional regions is achieved by stimulation of correlated events.The image reconstructed data were obtained using a multichannel synchrotron detection system.Experimental results show that the proposed method can achieve imaging of neural blood flow regulation in cortical functional regions.