Numerical and Experimental Simulations as Symbiotic Tools for Solving Complex Biothermal Problems

In the design of medical devices, the use of numerical simulation, either with or without complementary experimentation, may lead to a more competent product. The experimentation in question may either be performed in vitro or in vivo. This paper conveys a case study in which the two methodologies, numerical simulation and in vitro experimentation used in tandem, enabled the evaluation of safety issues related to a heat-generating implant. The numerical simulation was implemented by means of ANSYS finite-element software employed in the transient mode. The experimental work provided information necessary for the execution of the simulation and, therefore, was performed as the first phase of the research. The implant is of the type that is equipped with a short-lived battery that requires intermittent recharging. The recharging is accomplished by means of an antenna that is externally mounted on the skin surface. The antenna is the primary of a transformer, and the implant contains the secondary of the transformer. During the recharging period of the battery, heat is generated in both the antenna and the implant. By the symbiotic use of the experimental results and the numerical simulation, time-dependent temperatures were determined in the tissue that is situated in the neighborhood of the implant and the antenna. These temperatures were evaluated from the standpoint of possible tissue damage.