The electromagnetic scattering problem posed by the interaction of the magnetic resonance imaging (MRI) RF field with a medical implant in tissue is explored. An exact formulation is computationally expensive since the domain includes all of the body tissue, the implant, the air region, and the surfaces of the RF coil conductors. It is shown that a division of the problem into two parts makes it more amenable to a numerical computation. In the first part, the RF field in the presence of body tissue only is found, and in the second part, the RF field that has already been computed is used as the incident field in the presence of the implant. Taking this incident field approximation into account, a domain simplification approximation is presented. A nonhomogeneous tissue layer surrounding the implant is considered and it is shown that then it is no longer necessary to integrate over all of the body tissue, and that the errors introduced due to this approximation are small enough to be considered as negligible. Numerical results validating the approximations are also presented.
S. A. Mohsin, N. M. Sheikh, F. Mahmood, W. Abbas. (2010) General Considerations Regarding Scattering of the MRI RF Field by Implanted Medical Devices, Pakistan Journal of Engineering and Applied Sciences, Volume 6, Issue 1.