Computer modeling and simulation of implantable medical device heating due to MRI gradient coil fields

For patients with implantable medical devices, the ability to safely undergo MRI scanning is critical to ensuring the highest standard of care. The gradient coils of an MRI generate kilohertz frequency, time varying magnetic fields. These magnetic fields induce a voltage on the external case of metallic, implantable medical devices through electromagnetic induction. Since the magnetic field generated by a gradient coil is time varying, the induced voltage results in the flow of eddy currents which can cause heating effects. These heating effects have been successfully modeled using ANSYS Maxwell and ANSYS Mechanical software packages. The multi-physics simulation and solution used ANSYS Maxwell for electromagnetic field simulation and ANSYS Mechanical for the transient thermal simulation while utilizing ANSYS Workbench to integrate the models. To validate the model, simulations and physical testing were completed on a number of samples that varied in size and material. The model was then used to simulate the impact of implant size (both radius and thickness) on MRI gradient induced heating. These results can be used to support MRI safety assessments and design choices for a range of implantable medical devices. The current regulatory landscape requires extensive safety testing that is often expensive and time consuming. While the complicated question of medical device heating due MRI gradient coil fields remains open, computer simulation is now a proven tool that can provide easier and more thorough analysis for future evaluations