Derivation of chromophore concentrations in turbid media using the rate of change of optical attenuation with respect to wavelength

Abstract

A spectroscopic method is investigated for estimating the concentrations of absorbers in highly scattering media using measurements of the rate of change of optical attenuation with wavelength. Such measurements are independent of absolute intensity and thus may be significantly less influenced by changes in coupling which often cause artefacts in medical applications of near-infrared spectroscopy. The method has been explored using a combination of stochastic (Monte Carlo) and analytical (diffusion-based) models and experiments on samples of turbid fluids. Results suggest that the method is highly tolerant of changes in the measurement geometry. The accuracy of the derived concentrations of absorbers can be strongly influenced by the wavelength dependence of scattering, and an ad-hoc, empirically-derived correction for this dependency has been investigated and implemented with some success.