The aim of this study was to determine the optical absorption and scattering properties in a large Swedish cohort including 1765 subjects. The study was performed in the Linköping site within the national multicenter Swedish CArdioPulmonary bioImage Study (SCAPIS), a world unique study including detailed imaging and functional analysis of heart, vessels and lungs in 30 000 men and women in Sweden to predict and prevent cardiovascular disease and chronic obstructive pulmonary disease.
The subjects, men and women between 50 and 64 years old, were randomly selected and recruited from the population registry in Sweden. Measurements on the volar forearm were performed at baseline and during a systolic occlusion provocation with an integrated system, including spatially resolved diffuse reflectance spectroscopy and laser Doppler flowmetry. Data were analyzed with an inverse Monte Carlo algorithm, accounting for both scattering, geometrical and absorbing properties of the tissue. The absorption coefficient was assumed to differ between the epidermis and the two dermis layers, while the reduced scattering coefficient was equal in all layers.
The reduced scattering coefficient (@ 650 nm) was (M ± SD) = 1.68 ± 0.34 mm-1. Gender was found to significant change the fraction of small scattering particles and the reduced scattering coefficient. The absorption coefficient (@ 650 nm) for the dermis layers was 0.010 ± 0.005 mm-1. This large study on optical properties of skin can serve as reference values and provide new knowledge on how factors like gender, age, BMI etc. affect the optical properties.