Research On Modeling And Simulation Of Endoscopic Magnetoacoustic Tomography With Magnetic Induction

Biological magnetoacoustic tomography with magnetic induction(MAT-MI),a newly emerged functional imaging modality,combines the electromagnetic,ultrasonic and multi-physics detection and imaging technology.It has the advantages of good contrast of electrical impedance tomography and high spatial resolution of ultrasonography.It provides the variation of conductivity of biological tissues,which is helpful for the early detection of abnormal tissues.Endoscopic MAT-MI(EMAT-MI)combines MAT-MI and endoscopic detection techniques.It can directly detect the physiology and pathology of the luminal structures including nasal cavity,digestive tract and vessel,etc.This dissertation addresses the computer-based modeling and simulation of EMAT-MI transversal images.First,a cross-sectional lumen model with pathological tissue is constructed including the geometrical structure and related electromagnetic and acoustic parameters of the tissues.Second,the process of magnetic excitation is simulated obtaining the eddy current distribution of the imaged tissues.Third,the generation and propagation of the magnetoacoustic(MA)waves is simulated based on the distribution of the eddy current.Fourth,the polar map of the distribution of the acoustic source in the tissue surface is reconstructed with a time reversal algorithm.Finally,the polar map of the distribution of the conductivity is recovered,which is then transformed into the transversal view in a Cartesian coordinate system.With the proposed simulator,one can flexibly adjust the luminal model,change the electromagnetic and acoustic parameters of the model,and simulate the acoustic field of the multi-layer luminal tissues.The position,size and contours of the pathological tissues can be distinguished from the simulated images.