Image Reconstruction Of Conductivity On Magneto-acoustic Tomography With Magnetic Induction

The quantity and distribution of electric charge in biological tissues variy when the tissues are damaged or have pathological changes. Also the electrical properties of the pathological tissues such as electrical impedance, conductivity and dialectical coefficient are changed macroscopically. Since the differences between the normal tissue and the pathological tissue are obvious, the pathological changes could be detected noninvasivly by method of electrical properties functional imaging.It is of increasing interest to image the electrical impedance of biological tissues using noninvasive measurement. Efforts have been made to image the impedance distribution using various methods, such as electrical impedance tomography (EIT), magnetic resonance electrical impedance tomography (MREIT), Hall-effect-imaging (HEI) and magneto-acoustic tomography with magnetic induction (MAT-MI).Magneto-acoustic Tomography with Magnetic Induction is a noninvasive technique for imaging the electrical conductivity of biological tissue. The method uses two magnetic fields:one static and one changing with time. The time-varying magnetic field induces eddy currents in the tissue, and these eddy currents interact with the static magnetic field to produce a Lorentz force that initiates ultrasonic waves. The goal of the method is to deduce the conductivity distribution from the acoustic signal.In this study, a two-layer concentric spherical model is established to simulate the tumor tissue surrounded by health tissue, and also provides an assumptation that the spheres and the surrounding media is acoustically homogeneous. Mutual relations of the magneto-sound coupling effect and the coupling equations in the magnetic field are used to get the algorithms reconstructing the conductivity. Furthermore, the conductivity distribution is calculated when it is continuous as well as complex. Besides, simulation study is conducted to test the proposed model and validate the performance of the reconstructed algorithms. The simulating results indicate that using signal processing method conducted in this paper can image conductivity boundaries of the sample in the scanning cross section. The computer simulating results suggests the feasibility of applying the method of Magneto-acoustic Tomography with Magnetic Induction for tumor imaging. To validate the mathematic model provided in the paper. The experimental setup is designed to detect the acoustic signal excited by the two magnetic fields.