Theoretical And Experimental Research On Inductive Magnetoacoustic Coupling Imaging Based On Ultra-fast Active Detection Technology

Cancer has become a premier killer of human health.Tumor mechanism studies have shown that angiogenesis can lead to the changes in tissue electrical conductivity.The difference between the conductivity property of tumor tissue and normal tissue,which makes it valuable to the research of tumor diagnosis with early stages.Magneto-acoustic Tomography(MAT)is a newly proposed functional imaging approach to noninvasive electrical conductivity imaging of biological.It can be divided into Magneto-acoustic Tomography with Applied Current(MAT-AC)and Magneto-acoustic Tomography with Magnetic Induction(MAT-MI).The common method in MAT-MI uses KV pulse with ?s width as a stimulation to achieve mm resolution,that makes the stimulator hard to design for manufacture,and the energy conversion rate is low,the safety of the instrument is also a problem.The ultrasonic signals are collected by the single-channel transducer around the object,the acquisition time is long.The disturbance by the high frequency stimulated pulse will limit the image quality.Therefore,a new imaging method are introduced and studied in this paper: the method adopted 0.1KHz continuous sine signal to stimulate the model to emit the dynamic electromagnetic field,which simplified the imaging system.the Doppler phase-shift estimation is used to estimate the small tissue displacements,and the multi-channel ultrasonic data acquisition system is used to sample vibration signals,which makes the acquisition efficient.The reconstructed method will be used to reconstruct the image of the conductivity of the medium.This project analyzed a mathematical model of electromagnetic field-solid displacement field which was established based on Maxwell's equations and Navier's equations.The simulation study was carried out on Comsol Multiphysics5.2a software.A three-dimensional coil stimulator and a tumor conductivity model were investigated,the distribution of induced current and the Lorentz force inside the spheres with different conductivity were presented.Furthermore,the conductivity ratio,the volume ratio and the relative position between the healthy biological tissue and the tumor tissue were introduced to get its influence on the induced current.The experiment system has been designed and established,we measure the small displacements of phantoms.The measurement result was consentient with the theoretical derivation and simulation results.The simulation results suggested that the parallel coils has better magnetic field characteristics.The induced current is related to the conductivity ratio((29)2),volume ratio((29)0.3),and relative position.The experimental results suggested that the conductivity information is contained in the displacement signal,proving the feasibility that the conductivity could be reconstructed from displacement signals.