Conductivities tomography with the interactions of magnetic field, electrical field, and ultrasound field is presented in this paper. We utilize a beam of ultrasound in scanning mode instead of the traditional ultrasound field generated by point source. Many formulae for the reconstruction of conductivities are derived from the voltage signals detected by two electrodes arranged somewhere on tissue＇s surface. In a forward problem, the numerical solutions of ultrasound fields generated by the piston transducer are calculated using the angular spectrum method and its Green＇s function is designed approximately in far fields. In an inverse problems, the magneto-acousto-electrical voltage signals are proved to satisfy the wave equations if the voltage signals are extended to the whole region from the boundary locations of transducers. Thus the time-reversal method is applied to reconstructing the curl of the reciprocal current density. In addition, a least square iteration method of recovering conductivities from reciprocal current densities is discussed.
Magnetoacoustic tomography combines the advantages of electrical impedance tomography with sonography.It can reconstruct conductivity images of biological tissue with high spatial resolution and high contrast.In addition,magnetoacoustic tomography is a new nondestructive functional imaging technology,with which we can realize the early diagnosis of human diseases.In this paper,through theory analysis we deduced the analytical formula of acoustic pressure.Computer simulation and experimental studies on magnetoacoustic tomography with current injection(MAT-CI)were made,and a copper ring was used as the model for the simulation and experiment.Experimental setup and methods are introduced,and the acoustic signals and the image of a metal object by means of MAT-CI are presented.Results of the simulation and experiment were in a good agreement.The reconstructed image of an acoustic source can reflect the conductivity information of a sample.The conductivity distribution of a sample can be obtained by means of MAT-CI.The results provide foundations of study on a model with complex conductivity distribution and tissues for MAT-CI.
