title: Study of a wireless power transmission system for an active capsule endoscope.
abstract: BACKGROUND
  An active capsule endoscope (ACE) will consume much more energy than can be power by batteries. Its orientation and position are always undetermined when it continues the natural way down the gastrointestinal track.
  
  
  METHODS
  In order to deliver stable and sufficient energy to ACE safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a Helmholtz primary coil outside and a multiple secondary coils inside the body. The Helmholtz primary coil is driven to generate a uniform alternating magnetic field covering the whole of the alimentary tract, and the multiple secondary coils receive energy regardless of the ACE's position and orientation relative to the generated magnetic field. The human tissue safety of the electromagnetic field generated by transmitting coil was evaluated, based on a high-resolution realistic human model.
  
  
  RESULTS
  At least 310 mW usable power can be transmitted under the worst geometrical conditions. Outer dimensions of the power receiver, 10 mm diameter x 12 mm; transmitting power, 25 W; resonant frequency, 400 kHz. The maximum specific absorption rate (SAR) and current density of human tissues are 0.329 W/kg and 3.82 A/m(2), respectively, under the basic restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP).
  
  
  CONCLUSIONS
  The designed wireless power transmission is shown to be feasible and potentially safe in a future application.
authors.affiliation: Institute of Precise Engineering and Intelligent Microsystems, Shanghai Jiaotong University, Shanghai, People's Republic of China. rain3034@gmail.com
authors.forename: Wenhui
authors.initials: W
authors.lastname: Xin
authors.forename: Guozheng
authors.initials: G
authors.lastname: Yan
authors.forename: Wenxin
authors.initials: W
authors.lastname: Wang
mesh_terms: D053705:Capsule Endoscopes; D053704:Capsule Endoscopy / Q000379:methods*; D004553:Electric Conductivity; D011211:Electric Power Supplies; D004574:Electromagnetic Fields; D004582:Electronics, Medical / Q000295:instrumentation*; D004867:Equipment Design; D006801:Humans; D008953:Models, Anatomic; D008962:Models, Theoretical