Abstract
A multi-spectral diffuse reflectance imaging method based on a single snap shot of Red-Green-Blue images acquired with the exposure time of 65 ms (15 fps) was investigated for estimating melanin concentration, blood concentration, and oxygen saturation in human skin tissue. The technique utilizes the Wiener estimation method to deduce spectral reflectance images instantaneously from an RGB image. Using the resultant absorbance spectrum as a response variable and the extinction coefficients of melanin, oxygenated hemoglobin and deoxygenated hemoglobin as predictor variables, multiple regression analysis provides regression coefficients. Concentrations of melanin and total blood are then determined from the regression coefficients using conversion vectors that are numerically deduced in advance by the Monte Carlo simulations for light transport in skin. Oxygen saturation is obtained directly from the regression coefficients. Experiments with a tissue-like agar gel phantom validated the method. In vivo experiments on fingers during upper limb occlusion demonstrated the ability of the method to evaluate physiological reactions of human skin.
Highlights
Quantitative evaluation of the melanin and blood concentrations and the blood oxygenation is important for detecting various skin diseases including cancers, monitoring health status and tissue metabolism, and evaluating convalescence
Multi-spectral imaging based on diffuse reflectance spectroscopy has been widely employed for evaluating the spatial distribution of chromophore contents in living tissue using a series of discrete narrow-band filters or a liquid crystal tunable filter [11,12,13]
A simple method for imaging concentrations of melanin and blood and imaging oxygen saturation in human skin tissue based on the diffuse reflectance images at six wavelengths
Summary
Quantitative evaluation of the melanin and blood concentrations and the blood oxygenation is important for detecting various skin diseases including cancers, monitoring health status and tissue metabolism, and evaluating convalescence. A simple method for imaging concentrations of melanin and blood and imaging oxygen saturation in human skin tissue based on the diffuse reflectance images at six wavelengths (500, 520, 540, 560, 580 and 600 nm) using multiple regression analysis aided by the Monte Carlo simulations has been previously proposed [14]. In this method, use of a monochromatic charge coupled device (CCD) camera with mechanical rotatory filters required 12 s for reflectance images at the six wavelengths
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