Forward Problem Of Magnetoacoustic Tomography With Magnetic Induction Based On Characteristics Of Acoustic Transducer

Magneto-acoustic tomography with magnetic induction (MAT-MI) is a newly emerged functional imaging method combining high contrast of EIT and high-resolution of Ultrasonic Imaging, which is sensitive to the electric conductivity variation of tissue. The advantage of MAT-MI is that the time-varying pulsed magnetic field will be little affected by the surface of the low conductivity tissues, as well as the simple reconstruction algorithm. In MAT-MI, the time-varying pulsed magnetic field induces an eddy current in the tissue. Acoustic source originates from Lorentz force generated by the coupling effect of the induced current and the static magnetic field inside the tissue. Then, acoustic waves propagate and spread out, at the meantime, the acoustic signals could be detected by the acoustic transducers outside the tissue. With the collected ultrasound signals, we can reconstruct the conductivity images.In this paper, we established the simulation model for MAT-MI forward problem based on3D phantom model of CT firstly. And also, we gave the relationship between the induced electric field and the conductivity inside model, which is combined with the electromagnetic theory and finite element analysis. The results showed that the induced current is zero at the center of the object and varied rapidly on the boundary of different conductivity.Secondly, acoustic field forward problem of MAT-MI is conducted based on characteristics of acoustic transducer, and the generating, transmitting and receiving mechanism of MAT-MI acoustic source is also derived. Adopted acoustic dipole model and the characteristics of acoustic transducer, we established the equation of the acoustic pressure, which is based on characteristics of acoustic transducer. Subsequently, we presented the simulation results of the acoustic signal. The results showed that the signal received by the acoustic transducer could be deeply affected by acoustic pressure field distribution of the acoustic transducer and the directivity of acoustic dipole. Therefore, this study will provide a basis for the experimental study of MAT-MI and the reconstruction of conductivity distribution.Furthermore, in order to validate the simulation model and algorithm of MAT-MI, a simple copper ring model experiment is carried on. The results show that the data from experiment and simulation are identical within tolerance. Anyway, application of the model and algorithm may provide theoretical guidance for the experimental design and basis for the image reconstruction.