title: In vivo measurements of cutaneous melanin across spatial scales: using multiphoton microscopy and spatial frequency domain spectroscopy.
abstract: The combined use of nonlinear optical microscopy and broadband reflectance techniques to assess melanin concentration and distribution thickness in vivo over the full range of Fitzpatrick skin types is presented. Twelve patients were measured using multiphoton microscopy (MPM) and spatial frequency domain spectroscopy (SFDS) on both dorsal forearm and volar arm, which are generally sun-exposed and non-sun-exposed areas, respectively. Both MPM and SFDS measured melanin volume fractions between (skin type I non-sun-exposed) and 20% (skin type VI sun exposed). MPM measured epidermal (anatomical) thickness values ~30-65 μm, while SFDS measured melanin distribution thickness based on diffuse optical path length. There was a strong correlation between melanin concentration and melanin distribution (epidermal) thickness measurements obtained using the two techniques. While SFDS does not have the ability to match the spatial resolution of MPM, this study demonstrates that melanin content as quantified using SFDS is linearly correlated with epidermal melanin as measured using MPM (R² = 0.8895). SFDS melanin distribution thickness is correlated to MPM values (R² = 0.8131). These techniques can be used individually and/or in combination to advance our understanding and guide therapies for pigmentation-related conditions as well as light-based treatments across a full range of skin types.
authors.affiliation: University of California, Beckman Laser Institute, Laser Microbeam and Medical Program, Irvine, California, 92612, United States.
authors.forename: Rolf B
authors.initials: RB
authors.lastname: Saager
authors.affiliation: University of California, Beckman Laser Institute, Laser Microbeam and Medical Program, Irvine, California, 92612, United States.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Balu
authors.affiliation: University of California, Beckman Laser Institute, Laser Microbeam and Medical Program, Irvine, California, 92612, United States.
authors.forename: Viera
authors.initials: V
authors.lastname: Crosignani
authors.affiliation: University of California, Beckman Laser Institute, Laser Microbeam and Medical Program, Irvine, California, 92612, United States.
authors.forename: Ata
authors.initials: A
authors.lastname: Sharif
authors.affiliation: University of California, Beckman Laser Institute, Laser Microbeam and Medical Program, Irvine, California, 92612, United States.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Durkin
authors.affiliation: University of California, Beckman Laser Institute, Laser Microbeam and Medical Program, Irvine, California, 92612, United StatesbUniversity of California, Department of Dermatology, Irvine, California, 92697, United States.
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Kelly
authors.affiliation: University of California, Beckman Laser Institute, Laser Microbeam and Medical Program, Irvine, California, 92612, United States.
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Tromberg
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008543:Melanins / Q000032:analysis*; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*; D012867:Skin / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D008543:Melanins