Research On Detection And Imaging Methods Of Impedance Topographic Map Of Brain Functional Area

Electromagnetic detection provides an important research method for brain functional activity and state monitoring.The neural activity of the brain is often accompanied by the rapid increase of local cerebral blood flow.Because the conductivity of blood is higher than that of other brain tissues,the change of local cerebral blood flow will lead to the change of electrical impedance in the corresponding region of the brain.Therefore,the impedance measurement of the regulation process of cerebral blood circulation can indirectly characterize the functional neural activity of the brain.Based on the related research of cerebral impedance,aiming at the defects of the existing brain function detection technology,such as lack of comprehensive,continuous and certain depth detection ability,this paper proposes a cerebral blood flow impedance detection and imaging method based on distributed electrode array.The characteristics of cerebral blood flow impedance are characterized by topographic map method and the reconstruction of distributed cerebral blood flow impedance image is realized.Firstly,according to the regulation mechanism of cerebral nerve blood flow,the mathematical model between cerebral vascular volume,vascular compliance and blood flow impedance were established.Based on the principle and method of cerebral blood flow impedance detection,the brain simulation model and electrode array model were established.According to the different segmentation methods and electrode grouping methods of the model,the dynamic impedance simulation experiment of cerebral blood flow was designed to simulate the dynamic regulation process of cerebral blood flow when vascular compliance changes in different brain functional areas.Secondly,the cerebral blood flow impedance data were calculated through the simulated potential results,the characteristic parameters were extracted and analyzed,and the dynamic change process of the characteristics of cerebral blood flow impedance signal was characterized by topographic map method.The simulation results showed that the differential peak value and impedance change of cerebral blood flow impedance signal are not suitable for topographic map imaging,and the peak time interval between impedance differential and conduction pressure can be used as an effective feature to detect the process of cerebral blood flow neuroregulation.Mapping this feature to topographic map can obtain the position information of blood flow change under neuroregulation.Thirdly,the problem of distributed cerebral blood flow impedance image reconstruction was studied,and the corresponding sensitivity matrix solution method was proposed for the simplified linear model of the positive problem.Based on the measurement results of brain impedance static simulation experiment,the inverse problem of distributed cerebral blood flow impedance imaging was solved by Landweber algorithm,Tikhonov algorithm and IHT algorithm,and the quality of the reconstructed image was analyzed.Imaging results showed that the three algorithms can realize distributed impedance image reconstruction,and Tikhonov combine with IHT algorithm has better image quality and less artifacts.Finally,the images obtained by topographic map and image reconstruction are compared and analyzed.The experimental results showed that the impedance detection and imaging method proposed in this paper can detect the neural activity process of cerebral blood flow,which provides a safe and continuous detection method for the study of brain function.The combination of the two imaging methods can provide more comprehensive characteristics of cerebral blood flow impedance signal and locate the change area of cerebral blood flow impedance,which is of great significance for brain function imaging and real-time continuous monitoring of cerebral blood flow.