Application of the method of auxiliary source to the sensitivity analysis of high frequency magnetic induction tomography system

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. In MIT, current-carrying coils are used to induce eddy currents in the object and the induced voltages are sensed with receiving coils. When the driving frequency is significantly high, metallic targets with high conductivity between the coils can be treated as perfect electric conductors (PEC) with negligible errors. Boundary Element Method (BEM) based on integral formulations becomes an effective way to analyze this kind of scattering problems since meshes are only required on the surface of the object. But how to deal with the singular integral, which is a heavy burden for the computation, is a difficult issue unlikely to avoid. The method of auxiliary source (MAS) introduces the concepts of auxiliary surface and auxiliary source which avoid the computation of singular integrals. In contrast to the BEM, the MAS is more simple and fast for solving the PEC scattering problem in high MIT system. In this paper, the formula of sensitivity distribution was obtained by MAS with high efficiency and accuracy and then simulations by MATLAB were programmed. According to the good agreement of these results obtained by different numerical methods, we can know that MAS is an effective way to analyze the sensitivity distributions of high frequency MIT system.