In vivo characterization of structural and optical properties of human skin by combined photothermal radiometry and diffuse reflectance spectroscopy

Monitoring of Hemodynamics in Human Skin Using Pulsed Photothermal Radiometry and Optical Spectroscopy

“…As can be seen from our results, compiled in table 1, the extracted skin parameter values corresponding to intact healthy skin are within physiologically plausible ranges. This supports our earlier experience with the same or very similar analyses, also including other volunteers [1][2][3]9,10]. Specifically, e.g., the fractional blood content is higher in the papillary as compared to reticular dermis, while the oxygenation level in the former is lower, in agreement with earlier reports from other groups [11,12].…”

“…The applied optical model of skin assumes four optically homogeneous layers, representing the epidermis, papillary and reticular dermis, and subcutis (adipose; see figure 1). Determination of the absorption properties of each layer in relation to the fractional contents of the included chromophores was described in detail earlier [1][2][3]6].…”

“…The applied light is absorbed well by both epidermal melanin and hemoglobin in dermal vasculature. The radiant exposure was estimated to ∼0.30 J/cm at the effective spot size of ~5 mm [1][2][3].…”

“…Mid-IR emission from the tissue surface was recorded with a fast IR camera (SC7500 by FLIR Systems Inc.; λ = 3.5-5.1 µm) at a rate of 1000 frames per second. PPTR signals were obtained by lateral averaging of the radiometric data over a suitable area of interest (typically 1 x 1 mm 2 ) and subtracting the baseline value [1][2][3]. The manufacturer provided calibration system (Hypercal TM ) was used for conversion of raw signal amplitudes to radiometric temperature values.…”

“…The experimental data are fitted with predictions of a dedicated numerical model of light transport in strongly scattering medium (Monte Carlo) using a four-layer model of skin. This approach allows assessment of the epidermal and dermal thickness, chromophore contents (e.g., melanin, oxy-and deoxy-hemoglobin), as well as scattering properties of both skin and subcutis [1][2][3].…”