Numerical solution of the general 3D eddy current problem for magnetic induction tomography (spectroscopy)

Abstract

Magnetic induction tomography (MIT) is used for reconstructing the changes of the conductivity in a target object using alternating magnetic fields. Applications include, for example, the non-invasive monitoring of oedema in the human brain. A powerful software package has been developed which makes it possible to generate a finite element (FE) model of complex structures and to calculate the eddy currents in the object under investigation. To validate our software a model of a previously published experimental arrangement was generated. The model consists of a coaxial coil system and a conducting sphere which is moved perpendicular to the coil axis (a) in an empty space and (b) in a saline-filled cylindrical tank. The agreement of the measured and simulated data is very good when taking into consideration the systematic measurement errors in case (b). Thus the applicability of the simulation algorithm for two-compartment systems has been demonstrated even in the case of low conductivities and weak contrast. This can be considered an important step towards the solution of the inverse problem of MIT.

Forward modelling of magnetic induction tomography: a sensitivity study for detecting haemorrhagic cerebral stroke

“…Previous FE simulations of the eddy-current problem for biomedical applications in MIT have been reported [11]; these employed the A -A formulation and included the displacement term. The same group reported on the feasibility of detecting cerebral oedema with MIT using a simplified four-layered head model with a spherical region of raised conductivity simulating the oedema [12].…”

Absolute Conductivity Reconstruction in Magnetic Induction Tomography Using a Nonlinear Method

“…The edge finite element method (edge FEM) has advantages over nodal elements for vector field computation in the eddy current problem [1]. Edge FEM has been employed for the medical and industrial MIT forward problem [20], [30]. Solving the forward problem of MIT using a scalar field has been reported by [9].…”

“…Solving the forward problem of MIT using a scalar field has been reported by [9]. An eddy current formulation of A r , A r − V presented by [20] models the electric field in the conducting region as sum of the scalar field V and primary magnetic vector potential, and a reduced magnetic vector potential A r .…”

A QR Accelerated Volume-to-Surface Boundary Condition for the Finite-Element Solution of Eddy-Current Problems

“…The difficulty with this is twofold; one is the large number of unknowns and the second is matrix ill-conditioning. More sophisticated approaches include forming a magnetostatic problem in the nonconducing region using either the vector or scalar magnetic potential and coupling the two finite element solutions [6] [12], or employing a surface integral equation to correctly model the global boundary condition [1] [2] [13].…”