Surrogate human tissue temperatures resulting from misalignment of antenna and implant during recharging of a neuromodulation device

Objectives: A synergistic experimental and numerical investigation has provided quantitative information on the response of surrogate human tissue temperatures to misalignment of the implant and antenna of neuromodulation devices during recharging. Materials and Methods: The experimental phase of the work provided information on the rates of heat transfer from the implant and the antenna to their respective surroundings. The heat transfer data were used as input to a biothermal model from which tissue temperature distributions were obtained. Results: It was found that misalignment increases tissue temperatures compared with those for the aligned case for all of the investigated devices. These increases ranged from 0.5°C to 5.3°C. Conclusion: Notwithstanding these increases, the lowest temperatures were attained by the Restore Ultra device for all operating conditions. The temperature levels achieved by the Precision Plus and Eon Mini devices were found to be greater than those for the Restore Ultra but their relative rankings depend on the thermal boundary conditions and the duration of the recharging period. The foregoing rank ordering was validated by a sensitivity study in which the heat transfer data inputted to the numerical simulation was varied systematically. The aforementioned comparisons correspond with identical recharging periods for all of the devices.