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The least-squares fitting of transport spectra obtained by an optical fiber spectrometer using a library of optical properties for oxy- and deoxy-hemoglobin and for water, and using a simple expression for scattering is very useful. Additional absorbing chromophores like bilirubin and protoporphyrin IX can be added as needed.
The algorithm takes advantage of all information at various wavelengths in a cooperative way as it fits for the blood (B), oxygen saturation (S), bilirubin (P), and scattering amplitude (a) which scaled the Rayleigh + Mie scattering pattern of skin. Hence, the algorithm is more immune to noisy data.
Typical fitting requires only a few seconds using MATLAB, and faster code can be written in C, C++ or Java.
The combination of an inexpensive optical fiber spectrometer and this simple analysis provide a low-cost and convenient approach toward measuring tissue optical properties