Journal of Yeungnam Medical Science

Review

Implantable Functional Electrical Stimulation with Inductive Power and Data Transmission System.: Joon Ha Lee; Yeungnam Univ J Med. 2007;24(2):97-106. Published online December 31, 2007; DOI: https://doi.org/10.12701/yujm.2007.24.2.97

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Abstract PDF: Functional electrical stimulation (FES) has developed over the last 35 years to become a scientifically, technologically and clinically recognized field of interest in clinical medicine. FES has been applied to locomotion, grasping, ventilation, incontinence, and decubitus healing. However, all of these achievements illustrate the initial applications of FES; its true potential has not yet been realized. Recently, FES systems, which are miniaturized stimulation devices, have been utilized in the clinical setting. However, because the stimulating electrodes of the current FES devices are percutaneous electrodes, which are susceptible to wire breakage, and skin infection an implantable FES stimulating electrode has been introduced in the U.S. and Japan. In the present study, an external power supply method using radio frequency (RF) coupling and data transmission was developed for the control of the implantable FES device. In addition, we review the current understanding of FES devices and their application in clinical medicine.

Original Article

A Transcutaneous Energy and Data Transmission for Implantable FES Devices: Joon Ha Lee; Yeungnam Univ J Med. 2007;24(2 Suppl):S472-480. Published online December 31, 2007; DOI: https://doi.org/10.12701/yujm.2007.24.2S.S472

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Abstract PDF: Background
：Inductive coupling links are frequently used for powering of implanted devices for functional electrical stimulation (FES) and cochlear. They are used in applications where implanted batteries are not capable of supplying a sufficient amount of power over the time of implantation or where continuous data exchange with external components is necessary like in a leg pacemaker. Materials and Methods：This paper describes an inductive power transmission link, which was developed for an implantable stimulator for direct stimulation of denervated muscles. The carrier frequency is around 1 MHz, the transmitter coil has a diameter of 46 mm, and the implant coil is 46 mm. Data transmission to the implant with amplitude shift keying (ASK) and back to the transmitter with passive telemetry can be added without major design changes.
Results
：We chose the range of coil spacing (2 to 30 mm) to care for lateral misalignment, as it occurs in practical use. If the transmitter coil has a well defined and reliable position in respect to the implant, a smaller working range might be sufficient. Under these conditions the link can be operated in fixed frequency mode, and reaches even higher efficiencies of up to 37%. The link transmits a current of 50 mA over a distance range of 2-15 mm with an efficiency of more than 20% in tracking frequency.
Conclusion
：The efficiency of the link was optimized with different approaches. A class E transmitter was used to minimize losses of the power stage. The geometry and material of the transmitter coil was optimized for maximum coupling. Phase lock techniques were used to achieve frequency tracking, keeping the transmitter optimally tuned at different coupling conditions caused by coil distance variations.

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