Trends in melanosome microcavitation thresholds for nanosecond pulse exposures in the near infrared

Morgan S. Schmidt; Paul K. Kennedy; Rebecca L. Vincelette; Michael L. Denton; Gary D. Noojin; Kurt J. Schuster; Robert J. Thomas; Benjamin A. Rockwell

doi:10.1117/1.JBO.19.3.035003

10 March 2014 Trends in melanosome microcavitation thresholds for nanosecond pulse exposures in the near infrared

Morgan S. Schmidt, Paul K. Kennedy, Rebecca L. Vincelette, Michael L. Denton, Gary D. Noojin, Kurt J. Schuster, Robert J. Thomas, Benjamin A. Rockwell

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Journal of Biomedical Optics, Vol. 19, Issue 3, 035003 (March 2014). https://doi.org/10.1117/1.JBO.19.3.035003

Abstract

Thresholds for microcavitation of bovine and porcine melanosomes were determined using nanosecond laser pulses in the near-infrared (1000 to 1319 nm) wavelength regime. Isolated melanosomes were irradiated by single pulses (10 or 50 ns) using a Q-switched Spectra Physics Nd:YAG laser coupled with an optical parametric oscillator (1000 to 1200 nm) or a continuum laser at 1319 nm. Time-resolved nanosecond strobe photography after the arrival of the irradiation beam allowed imaging of microcavitation events. Average fluence thresholds for microcavitation increased nonlinearly with increasing wavelength from ∼0.5 J/cm ² at 1000 nm to 2.6 J/cm ² at 1319 nm. Fluence thresholds were also measured for 10-ns pulses at 532 nm and found to be comparable to visible nanosecond pulse values published in previous reports. Calculated melanosome absorption coefficients decreased from 925 cm⁻¹ at 1000 nm to 176 cm ⁻¹ at 1319 nm. This trend was found to be comparable to the decrease in retinal pigmented epithelial layer absorption coefficients reported over the same wavelength region. Estimated corneal total intraocular energy retinal damage threshold values were determined in order to compare to current and proposed maximum permissible exposure (MPE) safe levels. Results from this study support recently proposed changes to the MPE levels.

CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Morgan S. Schmidt, Paul K. Kennedy, Rebecca L. Vincelette, Michael L. Denton, Gary D. Noojin, Kurt J. Schuster, Robert J. Thomas, and Benjamin A. Rockwell "Trends in melanosome microcavitation thresholds for nanosecond pulse exposures in the near infrared," Journal of Biomedical Optics 19(3), 035003 (10 March 2014). https://doi.org/10.1117/1.JBO.19.3.035003

Published: 10 March 2014

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