Melanin as a confounding factor in near infrared spectroscopy of skin

Blood oxygenation and blood volume are two clinically relevant parameters that can be determined noninvasively from near infrared in vivo spectra. As the number of medical applications based on near infrared technology grows, the necessity of extracting the same quality of information from all individuals increases as well. High epidermal melanin content masks the absorption of oxyhemoglobin and deoxyhemoglobin. Near infrared spectra were recorded in vivo from the forearm of subjects with light and highly pigmented skin. The spectra were analyzed using a modified Beer\u2013Lambert Law and a least squares classifier. In the first iteration the analysis included the chromophores oxyhemoglobin, deoxyhemoglobin and water; in the second iteration the analysis included melanin as an additional chromophore. Including melanin in the fit results in a statistically significant (P