Simulation research on the forward problem of magnetoacoustic concentration tomography for magnetic nanoparticles with magnetic induction in a saturation magnetization state

Abstract

Abstract Magnetoacoustic concentration tomography of magnetic nanoparticles (MNPs) with magnetic induction (MACT-MI) is a method that has been propsed recently for MNP concentration tomography for use in targeted therapy. This procedure has the advantages of being noninvasive, having high-resolution and providing quantitative estimation of MNPs. In order to further fundamentally increase the signal-to-noise ratio of the magnetoacoustic signal, the forward problem of MACT-MI in the saturation magnetization state was studied, especially the magnetization characteristics of MNPs, including the derivation of the force formula of MNPs in the saturation magnetization state and the relationships among the gradient of the external magnetic field, magnetic force, number concentration and sound pressure. Firstly, the magnetic force formula of MNPs in the saturation magnetization state was derived according to the classical Langevin theory of paramagnetism. Then, a 2D model was constructed to calculate the magnetic flux density, magnetic force and sound pressure. Finally, the 2D distribution diagram of magnetic force and sound pressure and its corresponding 1D curve were obtained. The simulation results showed that the saturation magnetic field produced by the Maxwell–Helmholtz coils made the MNPs magnetically saturated. Compared with the MNPs in an unsaturated magnetization state, the magnetic force of MNPs in the saturation magnetization state was stronger, and the stronger magnetic force could generate stronger magnetoacoustic signals, which made it possible to measure magnetoacoustic signals with higher signal-to-noise ratio. The research results can provide a research basis for the design of equipment for further MACT-MI experiment and clinical application.