Estimation of melanin and hemoglobin in skin tissue using multiple regression analysis aided by Monte Carlo simulation

Abstract

To estimate the concentrations of melanin and blood and the oxygen saturation in human skin tissue, we propose a method using a multiple regression analysis aided by a Monte Carlo simulation for diffuse reflectance spectra from the skin tissue. By using the absorbance spectrum as a response variable and the extinction coefficients of melanin, oxygenated hemoglobin, and deoxygenated hemoglobin as predictor variables, the multiple regression analysis gives regression coefficients. The concentrations of melanin and blood are determined from the regression coefficients using conversion vectors that are estimated numerically in advance, while the oxygen saturation is obtained directly from the regression coefficients. Numerical and experimental investigations were performed for layered skin tissue models and phantoms. Measurements of human skin were also carried out to monitor variations in the melanin and blood contents and oxygenation during cuff occlusion. The results confirmed the usefulness of the proposed method.

Rapid calculation of diffuse reflectance from a multilayered model by combination of the white Monte Carlo and adding-doubling methods

“…Figure 9(b) shows the time courses of C m , C oh , C dh , C th , and StO 2 during cuff occlusion at 250 mm Hg. The average values of C m and C th were 6.24 ± 0.06% and 0.211 ± 0.008%, respectively, in pre-occlusion (normal), which are close to typical values for Japanese subjects reported in the literatures [10,21,22]. The average value of 44.3 ± 3.4% for StO 2 in pre-occlusion agrees with the mean blood oxygen saturation of normal human subjects (range 30.2-52.4%) reported in the literatures [23].…”

“…(9) and (10). In the gLWMCS, the value of ξ in the model does not usually match the value of ξ used in phase 1; instead, R and T are derived by simple linear interpolation with Eqs.…”

“…Therefore, to shorten the calculation time, several methods have been considered for approximating the results of an MCS. For example, various studies have proposed diffusion approximation [3], hybrid diffusion and two-flux approximation [4], the path-integral method [2], and an empirical method aided by MCS [10]. However, in each of these methods, the difference from the MCS depends on the type of approximation, and often the applicable range of parameters is limited.…”

“…In the path-integral method, although the trajectories of the light are represented by the classical path, it is difficult to find an appropriate path for the various absorption and scattering coefficients [2]. Finally, although the empirical method aided by a MCS can estimate the chromophore concentrations over a wide range, it is not optimized for the estimation of the reflectance [10].…”

Skin cancer detection using laser imaging

“…Titanium dioxide powder is widely accepted as a scatterer in the near-infrared range [85] which is inexpensive and safe. Instant coffee can also be used as a good absorber of light in this frequency range [176].…”