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In Vivo Experimental Study of Thermal Problems for Rechargeable Neurostimulators


  • Conflict of interest: The authors reported no conflicts of interest.
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  • Financial support: This study was supported by National Natural Science Foundation of China (Grants no. 51125028, 51077083, 51061160501, 61001008, and 60906050) and by Tsinghua University Initiative Scientific Research Program (Grant no. 2009THZ01010).



Eddy currents in the metal shell and copper losses in the coils generate heat in rechargeable neurostimulators, which increases the temperature of the adjacent tissue, potentially causing thermal damage of implant patients. Hence, there is an urgent need for a simple self-help method to measure the temperature of such subcutaneous devices.

Materials and Methods

A wireless rechargeable implant system was fabricated and tested with in vivo experiments in swine to measure the increasing temperatures of both the implant device and the adjacent skin. A total of three swine were used in the study with 13 wireless charging tests.


It was found that the temperatures of both the implant and the skin rose consistently with an approximately linear relationship in most of the charging time, demonstrating that the neurosimulator temperature could be estimated from the skin temperature. The equilibrium temperature differences are all less than 2°C.


A convenient method was then given to monitor the adjacent skin temperature to evaluate the thermal hazards with a skin temperature threshold of 41°C. The proposed approach can be easily implemented by an implant patient at home to reduce the thermal risk, ease patient anxiety, and improve clinical outcomes.