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Proceedings Paper

Effects of optical irradiation parameters on safe peripheral nerve stimulation with infrared light
Author(s): Elizabeth Katz; Do-Hyun Kim; Ilko Ilev; Victor Krauthamer
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Paper Abstract

Optical stimulation (OS) is a relatively novel approach for restoring function to the damaged nervous system. The effectiveness and safety of OS is dependent upon selecting the appropriate stimulation parameters. This involves stimulating neurons to their activation threshold while preventing laser-induced tissue injury. Although significant advances have been made in studying the efficacy of OS, safety parameters are still being developed. We have employed electrophysiological techniques to determine salient experimental parameters of safety that can be used to optimize OS. Extracellular recordings of compound nerve potentials were obtained from excised adult rat sciatic nerves. OS was accomplished with infrared pulsed Nd:YAG, Er:YAG and diode lasers that had peak wavelength emissions at 1.064 μm, 2.94 μm and 1.85 μm, respectively. Electrically evoked compound action potentials (E-CAPs) were assayed before and after laser irradiation to determine if OS affected E-CAPs. Injurious laser irradiation doses were observed at levels 2-3 fold greater than optical threshold, producing tissue hyalinization and decreases in the peak amplitude of E-CAPs. However, effects on electrical threshold and conduction velocity were negligible. At laser irradiation doses near optical threshold, low repetition rates of laser pulses produced a gradual increase in laser evoked CAP (L-CAP) amplitudes, suggesting a cumulative effect in the interactions between light and tissue. Higher repetition rates (5-10 Hz) at laser irradiation doses 2-3 fold above optical threshold produced a decrement in L-CAP and E-CAP amplitudes. These results suggest that laser pulse parameters have a direct impact on optical stimulation and damage thresholds.

Paper Details

Date Published: 23 February 2009
PDF: 8 pages
Proc. SPIE 7180, Photons and Neurons, 71800P (23 February 2009); doi: 10.1117/12.816718
Show Author Affiliations
Elizabeth Katz, U.S. Food and Drug Administration (United States)
Office of Device Evaluation (United States)
Do-Hyun Kim, U.S. Food and Drug Administration (United States)
Ilko Ilev, U.S. Food and Drug Administration (United States)
Victor Krauthamer, U.S. Food and Drug Administration (United States)

Published in SPIE Proceedings Vol. 7180:
Photons and Neurons
Anita Mahadevan-Jansen; E. Duco Jansen, Editor(s)

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