| Because of its excellent soft tissue imaging capability, Magnetic Resonance Imaging (MRI) is a desirable diagnostic modality. This modality, however, is presently denied to many patients with implanted medical devices due to adverse interaction of the device with the electromagnetic fields of the MRI system. The number of patients with implanted medical devices is growing each year, meaning a growing number of patients cannot receive the benefits of MRI during the normal course of their healthcare.;There are several hazards associated with MRI and active implantable medical devices (AIMD). One such adverse interaction of MRI with a device containing an elongated lead, such as a pacemaker or deep brain stimulation (DBS) system, is heating near the tissue-electrode interface due to the radiofrequency (RF) field. The most common MRI system in use at present is a 1.5 T MRI system, which uses a 64 MHz RF field generated by a birdcage coil.;In this study, a wire exposed to a plane wave is used to model the amplification of the electric field near an implanted medical device exposed to MRI. Plane wave models are shown to give good agreement with the results from the birdcage coil, but are easier to analyze computationally and analytically. Simulation and measurement are shown to confirm the existence of a resonant length in conductive media.;This work proposes a method of mitigating the RF heating near implanted medical devices during MRI. This method is based on a field reduction scheme, that is achieved by modifying the current distribution at the wire boundary. This method was demonstrated through implementation in the simplified structure of an insulated wire by controlling the surface resistance of the wire and the dielectric constant of the insulating material. The work is verified by comparing the results from a Moment Method technique with commercially-available software. While the work concentrates on simplified structures that can be well understood from an analytical approach, the method shown can be extended to the more complex geometry of an implanted lead. |
