Magnetic susceptibility artifacts in magnetic resonance imaging: calculation of the magnetic field disturbances

In magnetic resonance imaging, inhomogeneities of the static magnetic field lead to perturbations in the resulting images, called artifacts. The authors' goal is to compute numerically the disturbances induced by a material having magnetic properties different from that of the surrounding tissues. The method is linked to an artifact reconstruction model to get simulated images. This model needs very accurate results in a fine three-dimensional grid around the implant. The use of standard methods would lead to solve very large systems. The authors' method is based on a surface integral representation of the magnetic field. To implement it in an efficient way, an analytical expression is derived when the boundary of the domain can be meshed in flat panels. For curved surfaces a numerical quadrature scheme is implemented.