Derivation of absorption coefficient and reduced scattering coefficient with edge-loss method and comparison with video reflectometry method

Abstract

We derived the absorption coefficient (μa) and the reduced scattering coefficient (μs′) using the edge-loss method (ELM) and the video reflectometry method (VRM), and compared the results. In a previous study, we developed the ELM to easily evaluate the lateral spread in the skin; the VRM is a conventional method. The ELM measures the translucency index, which is correlated with μa and μs′. To obtain a precise estimation of these parameters, we improved the treatment of a white standard and the surface reflection. For both skin phantoms and actual skin, the values for μa and μs′ that we obtained using the ELM were similar to those obtained using the VRM, when μa/μs′ was less than or equal to 0.05 and the diffusion approximation was applicable. Under this condition, the spectral reflectivity is greater than 0.4. In this study, we considered wavelengths longer than 600 nm for Types III and IV of the Fitzpatrick scale. For skin, the repeatability errors of the parameters obtained with the ELM were smaller than those obtained with the VRM; this can be an advantage in field tests.