Absorption and reduced scattering coefficients in epidermis and dermis from a Swedish cohort study

Abstract

Significance: Knowledge of optical properties is important to accurately model light propagation in tissue, but in vivo reference data are sparse.

Aim: The aim of our study was to present in vivo skin optical properties from a large Swedish cohort including 3809 subjects using a three-layered skin model and spatially resolved diffuse reflectance spectroscopy (Periflux PF6000 EPOS).

Approach: Diffuse reflectance spectra (475 to 850 nm) at 0.4 and 1.2 mm source-detector separations were analyzed using an inverse Monte Carlo method. The model had one epidermis layer with variable thicknesses and melanin-related absorptions and two dermis layers with varying hemoglobin concentrations and equal oxygen saturations. The reduced scattering coefficient was equal across all layers.

Results: Median absorption coefficients (${\mathrm{mm}}^{-1}$) in the upper dermis ranged from 0.094 at 475 nm to 0.0048 at 850 nm and similarly in the lower dermis from 0.059 to 0.0035. The reduced scattering coefficient (${\mathrm{mm}}^{-1}$) ranged from 3.22 to 1.20, and the sampling depth (mm) ranged from 0.23 to 0.38 (0.4 mm separation) and from 0.49 to 0.68 (1.2 mm separation). There were differences in optical properties across sex, age groups, and BMI categories.

Conclusions: Reference material for skin optical properties is presented.

Keywords: absorption; cohort study; diffuse reflectance spectroscopy; optical properties; scattering; skin.