The multi-frequency responses and sensitivity calculation of broadband magnetic induction tomography system using the boundary element method

Abstract

Magnetic induction tomography (MIT) is an imaging technique based on the measurement of the magnetic field perturbation due to eddy currents induced in conducting objects exposed to an external magnetic excitation field. The time- or frequency-domain profile of the signal on the receiving coil reveals characteristics of the target such as shape, permeability, and conductivity. For frequencies in the MIT range, the transmitted field penetrates the target slightly. Though slight, the effect of this penetration also typically has a nonnegligible effect on the scattered field. In this scenario, we use the thin skin depth approximation (TSA) just inside the target surface. Boundary element method (BEM) is an appreciative approach since meshes are only required on the surface of the object. In this paper, we analyse the responses of different frequencies on the receiving coil and compute four typical sensitivity maps between the coil pairs in MIT system due to a TSA model. Also, the real part and the imaginary part of the sensitivity of different frequencies are computed respectively. From the comparison we can know that the sensitivity maps derived by BEM are in good agreement with the theoretical solution. Overall, BEM is an effective way to calculate the multi-frequency responses and sensitivity distributions of broadband frequency MIT system.