Stimulation Efficiency With Decaying Exponential Waveforms in a Wirelessly Powered Switched-Capacitor Discharge Stimulation System.

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2018-05

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Abstract

The purpose of this study was to test the feasibility of using a switched-capacitor discharge stimulation (SCDS) system for electrical stimulation, and, subsequently, determine the overall energy saved compared to a conventional stimulator. We have constructed a computational model by pairing an image-based volume conductor model of the cat head with cable models of corticospinal tract (CST) axons and quantified the theoretical stimulation efficiency of rectangular and decaying exponential waveforms, produced by conventional and SCDS systems, respectively. Subsequently, the model predictions were tested in vivo by activating axons in the posterior internal capsule and recording evoked electromyography (EMG) in the contralateral upper arm muscles. Compared to rectangular waveforms, decaying exponential waveforms with time constants >500 μs were predicted to require 2%-4% less stimulus energy to activate directly models of CST axons and 0.4%-2% less stimulus energy to evoke EMG activity in vivo. Using the calculated wireless input energy of the stimulation system and the measured stimulus energies required to evoke EMG activity, we predict that an SCDS implantable pulse generator (IPG) will require 40% less input energy than a conventional IPG to activate target neural elements. A wireless SCDS IPG that is more energy efficient than a conventional IPG will reduce the size of an implant, require that less wireless energy be transmitted through the skin, and extend the lifetime of the battery in the external power transmitter.

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10.1109/tbme.2017.2741107

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Lee, Hyung-Min, Bryan Howell, Warren M Grill and Maysam Ghovanloo (2018). Stimulation Efficiency With Decaying Exponential Waveforms in a Wirelessly Powered Switched-Capacitor Discharge Stimulation System. IEEE transactions on bio-medical engineering, 65(5). pp. 1095–1106. 10.1109/tbme.2017.2741107 Retrieved from https://hdl.handle.net/10161/23849.

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Grill

Warren M. Grill

Edmund T. Pratt, Jr. School Distinguished Professor of Biomedical Engineering

Our research employs engineering approaches to understand and control neural function. We work on fundamental questions and applied development in electrical stimulation of the nervous system to restore function to individuals with neurological impairment or injury.

Current projects include:
• understanding the mechanisms of and developing advanced approaches to deep brain stimulation to treat movement disorders,
• developing novel approaches to peripheral nerve electrical stimulation for restoration of bladder function, 
• understanding the mechanisms of and developing advanced approaches to spinal cord stimulation to treat chronic pain,
• understanding and controlling the cellular effects of transcranial magnetic stimulation, and
• design of novel electrodes and waveforms for selective stimulation of the nervous system.


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