Study On Sound Source Problem Of Magnetic Induction Magnetic Image Imaging

Magneto-acoustic tomography with magnetic induction (MAT-MI) is proposed as a new type of medical imaging technology in recent years. In MAT-MI, the tissue is located in a static magnetic field and a time-varying magnetic field. The time-varying magnetic field induces an eddy current in the tissue. Consequently, the tissue will emit ultrasonic waves by the Lorentz force. The ultrasonic signals are collected around the object to reconstruct images related to the electrical impedance distribution in the tissue. It is different from conventional medical ultrasound imaging technology, that MAT-MI is not only using in imaging of human tissue function, but also in continuous dynamic monitoring the function of human organs, compared to current electrical impedance imaging technology, MAT-MI is a non-contact treatment technology, without injecting current into biological (human) body, which avoiding the shielding effect and being harmless to human body, showing more advantages in medical diagnostics.So far, MAT-MI is still in stage of theory and experiment validation, most of the studies is only a mathematical physics model. Based on research with acoustic parameters (sound attenuation) model of biological tissue imaging studies is relatively less, from clinical application research also has a certain distance.The current research about sound field of MAT-MI technology neglected acoustic sound scattering sound absorption in the tissue. Without considering the impact of attenuation of sound, Most tissue model conditions are homogeneous, isotropic. But the organizational structure of the different components, the way of sound attenuation is a different. Therefore, characterizing different acoustic properties of biological tissue parameters in MAT-MI, need to be understood.Source generation mechanism of MAT-MI technology is followed that biological tissue is forced to vibration and emitted ultrasonic, The sound source is a power, With the forces of its work is closely related to the excitation field. Different ways of working, the forces and mechanisms of biological tissue will sound a difference. Currently the excitation field research is still in the initial validation phase, and it requires analyzing the way of exciting field and establishing contacts with the sound field problems.In MAT-MI, radiated sound field problem with power source is supposed to be the key to solve the ultrasonic transmission mechanism in biological tissue. In this paper, by using an acoustic model of biological tissue, scattering and absorption, acoustic vibrator model and forced vibration of theory, the following issues is described: 1. Through the introduction of biological tissue layered medium model, the relations of biological tissue structural anisotropy, the conductivity of different and acoustic scattering phenomenon is discussed. Combined with the organizational structure model, The solution of ultrasound propagation in the tissue is discussed in detail. Theoretical and methodological guidance is provided for issues related to the scattering of sound attenuation.2. Combined with acoustic scattering, sound absorption theory including classical absorption and relaxation absorption, the solution of sound attenuation problem in tissue would be discussed in details.3. Combined with the basic principles of MAT-MI technology, the object model is analyzed. The biological tissue is analyzed according to the law of electromagnetism. The biological tissue model is decomposed into ring structures, and the force of acoustic vibrator because of changing in the magnetic flux would be analyzed.4. Through the introduction of several different forced vibration,From the excitation field work and power, the cause of the sound source generation is analyzed. The contact of Incentive Mode and vibration is found that the forced vibration of vibrator is a combination of impulse forced vibration and damping vibration. The theoretical model guide for simulation of the forward problem and reconstruction of inverse problems.5. Combined with the MAT-MI technology theory, based on several different experiment designs, the theory that how to define the sound source and media is related with the shape and size of the excitation coil is proposed.