Research On Key Techniques For Multidimensional Detection Of Deep Intracranial Bioimpedance Magnetic Induction Signals

Magnetic induction tomography is a non-contact,non-invasive electrical impedance detection technology,which has a good application prospect in the detection of brain lesions.Aiming at the detection of deep craniocerebral tissue by the magnetic induction detection system,the research on the key technology of multi-dimensional detection of deep-brain impedance magnetic induction signals is conducted to improve the measurement system's excitation-detection depth and signal accuracy.First,the eddy current detection principle of magnetic induction detection technology and its development status at home and abroad are studied.In order to improve the detection accuracy of deep internal brain tissue by magnetic induction detection technology,a scheme with a focusing characteristic coil as the excitation coil of the magnetic induction system is proposed,and a simulation and experimental system of a double 8-shaped coil magnetic induction detection system is designed based on this.A multi-dimensional detection and evaluation method to verify the working performance of the system is given.Secondly,a magnetic induction simulation system model of a craniocerebral model and a double 8-shaped coil was established,and a circular coil simulation system was also established as a comparison scheme.The simulation calculations of the two detection system models were performed.By comparing the two system simulations,the driving electric field and magnetic field intensity and distribution generated by the system at the level of the craniocerebral brain were calculated.The detection effect of the lesion tissue at the location,and the magnitude of the phase difference of the lesion with different conductivity after the simulation system experiment,the results show that the double 8-shaped coil magnetic induction system has better performance for deep excitation-detection of the internal brain tissue.Thirdly,a hardware system for magnetic induction detection is designed,including excitation-detection coils,power amplification circuit with AD815 as the core,to provide larger driving signals for the excitation end of the experimental system;filter amplification with LT6600-20 and AD8130 as the main chip The circuit filters and amplifies the voltage signal induced by the detection coil.The phase detector circuit based on the AD8302 phase detector chip provides effective phase difference data for subsequent image reconstruction.Based on the above design,a hardware experiment platform for the magnetic induction detection system is established.Finally,the designed system is tested experimentally according to the experimental platform.First,the system stability test is performed,and the NaCl solution with a certain conductivity is used for the multidimensional detection experiment of the hardware system.The system's multi-point,multi-time,and multi-frequency experimental measurement results show that the double 8-shaped coil magnetic induction detection system designed in this paper,compared with the circular coil magnetic induction detection system,experimentally obtains the phase difference data and the change in the conductivity of the target detection object.The trend is positively correlated and the linearity is good.The amplitude of the measured phase data and the processed phase difference data is larger.