title: Trends in melanosome microcavitation thresholds for nanosecond pulse exposures in the near infrared.
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/cm2 at 1000 nm to 2.6  J/cm2 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.
authors.affiliation: 711th Human Performance Wing, Human Effectiveness Directorate, Bioeffects Division, Optical Radiation Branch, 4141 Petroleum Road, JBSA, Fort Sam Houston, Texas 78234.
authors.forename: Morgan S
authors.initials: MS
authors.lastname: Schmidt
authors.affiliation: 711th Human Performance Wing, Human Effectiveness Directorate, Bioeffects Division, Optical Radiation Branch, 4141 Petroleum Road, JBSA, Fort Sam Houston, Texas 78234.
authors.forename: Paul K
authors.initials: PK
authors.lastname: Kennedy
authors.affiliation: TASC Inc., 4241 Woodcock Drive, Suite B-100, San Antonio, Texas 78228.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Vincelette
authors.affiliation: TASC Inc., 4241 Woodcock Drive, Suite B-100, San Antonio, Texas 78228.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Denton
authors.affiliation: TASC Inc., 4241 Woodcock Drive, Suite B-100, San Antonio, Texas 78228.
authors.forename: Gary D
authors.initials: GD
authors.lastname: Noojin
authors.affiliation: TASC Inc., 4241 Woodcock Drive, Suite B-100, San Antonio, Texas 78228.
authors.forename: Kurt J
authors.initials: KJ
authors.lastname: Schuster
authors.affiliation: 711th Human Performance Wing, Human Effectiveness Directorate, Bioeffects Division, Optical Radiation Branch, 4141 Petroleum Road, JBSA, Fort Sam Houston, Texas 78234.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Thomas
authors.affiliation: 711th Human Performance Wing, Human Effectiveness Directorate, Bioeffects Division, Optical Radiation Branch, 4141 Petroleum Road, JBSA, Fort Sam Houston, Texas 78234.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Rockwell
mesh_terms: D000042:Absorption; D000818:Animals; D002417:Cattle; D057446:Hydrodynamics; D007259:Infrared Rays; D007834:Lasers / Q000009:adverse effects* / Q000592:standards; D020460:Melanosomes / Q000737:chemistry* / Q000528:radiation effects*; D036103:Nanotechnology / Q000379:methods*; D055213:Retinal Pigment Epithelium / Q000166:cytology; D013552:Swine