title: In vivo experimental study of thermal problems for rechargeable neurostimulators.
abstract: OBJECTIVE
  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.
  
  
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: School of Aerospace, Tsinghua University, Beijing, China.
authors.forename: Shaobo
authors.initials: S
authors.lastname: Chen
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Li
authors.forename: Weiming
authors.initials: W
authors.lastname: Wang
authors.forename: Bozhi
authors.initials: B
authors.lastname: Ma
authors.forename: Hongwei
authors.initials: H
authors.lastname: Hao
authors.forename: Luming
authors.initials: L
authors.lastname: Li
mesh_terms: D000818:Animals; D002058:Burns, Electric / Q000209:etiology*; D011211:Electric Power Supplies / Q000009:adverse effects*; D058542:Implantable Neurostimulators / Q000009:adverse effects*; D012881:Skin Temperature / Q000502:physiology*; D013552:Swine; D013696:Temperature; D013997:Time Factors
keywords: biological heating; in vivo experiment; neurostimulator; skin temperature; wireless charging