A generic optical fiber probe with a source fiber and a collection fiber can be modeled by a transport function T(ua, us') where ua is the absorption coefficient and us' is the reduced scattering coefficient.

The absorption ua is modeled as the superposition of contributions from blood, water, bilirubin, and background protoporphyrin IX.

The scattering is modeled as us' = a nm-b.

The behavior of T(ua, us') is well characterized by Mexp(-uaL), where M and L are functions of us'.

For skin sites, the role of epidermal melanin is modeled such that measurement = exp(-fmelua.melLepiT(ua, us'), where fmel is the volume fraction of melanosomes in the epidermis, ua.mel is the absorption coefficient of a melanosome, and Lepi is twice the epidermal thickness.

This general scheme appears to work for probes of varying geometries. The details of the transport function will vary, but the general form is the same.

Hence, it is possible to specify meaningful parameters characterizing a tissue from spectra acquired with a simple optical fiber spectrophotometer.

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