Medizinische Implantate und Chirurgie

Abstrakt

Low or Medium Frequency Magnetic Fields Simplified by Modeling of Implanted Medical Devices

Nitika Goel

When exposed to time-varying magnetic fields, such as those generated during certain diagnostic and therapeutic biomedical treatments, implanted medical devices with metallic filamentary closed loops (such as fixation grids, stents) produce electric currents. For low or medium frequency fields, a simplified method for efficiently computing these currents, estimating the altered electromagnetic field distribution in biological tissues, and evaluating the resulting biological effects is proposed. Decoupling the handling of the filamentary wire from the anatomical body is the foundation of the proposed method. In order to accomplish this, a circuital solution is used to investigate the metallic filamentary implant and is inserted into an electromagnetic field solution that involves biological tissues. The implant’s calculated Joule losses are then utilized as a forcing term for the bioheat Pennes’ equation-defined thermal problem. A reference solution to a model problem is used to validate the methodology. In realistic exposure scenarios, the proposed simplified methodology is found to be sufficiently accurate and simple to apply to closed loop wires in the low to intermediate frequency range. Analyzing a wide range of exposure scenarios for various types of small implants, including orthopedic grids and coronary and biliary stents, is made possible by this modeling tool.