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Journal of Biomedical Optics • Open Access

Temperature dependence of nanosecond laser pulse thresholds of melanosome and microsphere microcavitation

Paper Abstract

Melanosome microcavitation is the threshold-level retinal pigment epithelium (RPE) damage mechanism for nanosecond (ns) pulse exposures in the visible and near-infrared (NIR). Thresholds for microcavitation of isolated bovine RPE melanosomes were determined as a function of temperature (20 to 85°C) using single ns laser pulses at 532 and 1064 nm. Melanosomes were irradiated using a 1064-nm Q-switched Nd:YAG (doubled for 532-nm irradiation). For comparison to melanosome data, a similar temperature (20 to 65°C) dependence study was also performed for 532 nm, ns pulse exposures of black polystyrene microbeads. Results indicated a decrease in the microcavitation average radiant exposure threshold with increasing sample temperature for both 532- and 1064-nm single pulse exposures of melanosomes and microbeads. Threshold data and extrapolated nucleation temperatures were used to estimate melanosome absorption coefficients in the visible and NIR, and microbead absorption coefficients in the visible, indicating that melanin is a better absorber of visible light than black polystyrene. The NIR melanosome absorption coefficients ranged from 3713  cm−1 at 800 nm to 222  cm−1 at 1319 nm. These data represent the first temperature-dependent melanosome microcavitation study in the NIR and provide additional information for understanding melanosome microcavitation threshold dependence on wavelength and ambient temperature.

Paper Details

Date Published: 27 January 2016
PDF: 8 pages
J. Biomed. Opt. 21(1) 015013 doi: 10.1117/1.JBO.21.1.015013
Published in: Journal of Biomedical Optics Volume 21, Issue 1
Show Author Affiliations
Morgan S. Schmidt, Air Force Research Lab. (United States)
Paul K. Kennedy, Air Force Research Lab. (United States)
Gary D. Noojin, Engility Corp. (United States)
Robert J. Thomas, Air Force Research Lab. (United States)
Benjamin A. Rockwell, Air Force Research Lab. (United States)

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