Regional Difference of Water Content in Human Skin Studied by Diffuse-Reflectance Near-Infrared Spectroscopy: Consideration of Measurement Depth
Diffuse reflectance (DF) spectra in the 1250–2500 nm region were measured in vivo for the skin of the forehead, cheek, jaw, elbow, volar forearm, palm, knee, and heel of seven healthy volunteers, using a Fourier transform near-infrared (FT-NIR) spectrophotometer with a
fiber-optic probe. Apparent regional differences of water content in the skin, as estimated from the diffuse reflectance NIR spectra, are discussed in relation to the influence of measurement depth. The NIR spectra were collected with or without a 300 μm gap between the fiber-optic probe
and the skin surface. For comparison, in vitro NIR spectra of stratum corneum sheets equilibrated at 41, 50, 63, and 81% relative humidity, at 25 °C, were also obtained. There was a difference in the ratio of the two water bands centered near 1450 nm and 1900 nm between the contact
and non-contact measurements. In addition, regional differences of water content calculated from the peak height of the 1900 nm water band, which was normalized to the peak height of the 2175 nm amide band, were compared. The results of Monte Carlo simulation indicated that the apparent regional
differences arise at least in part from differences in the measurement depth due to differences in specular reflection at the skin surface and in the thickness of the stratum corneum.
MONTE CARLO SIMULATION;
Document Type: Research Article
Shiseido Research Center (Shin-Yokohama), Yokohama 224-8558, Japan
National Institute of Advanced Industrial Science and Technology, Tsukuba, 305-8564, Japan
Department of Chemistry and Research Center for Near Infrared Spectroscopy, School of Science and Technology, Kwansei Gakuin University, Sanda 669-1337, Japan
Publication date: January 1, 2006
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