Multichannel spectroreflectometry: a noninvasive method for assessment of on-line hemoglobin derivatives

Abstract

The goal of the current study was to introduce a mathematical method to derive hemoglobin, oxyhemoglobin and carboxyl-hemoglobin absorption factors from full spectrum reflectometry measurements of retinal microcapillaries. The mathematical equation that describes the spectral reflectometry function was expressed as a linear combination of several terms of S(i)(lambda) representing the spectral signature functions of hemoglobin, oxyhemoglobin, carboxyl-hemoglobin, ocular media, melanin, and a scattering factor. Contrary to the classical model, where the reflectometry function was expressed as an absorbance Ab(lambda)=log?(incident light(lambda)/reflected light(lambda)), in this model and system, it is proposed to express the reflectometry function from the eye structures as an absorption factor A(lambda)%=incident light(lambda)/reflected light(lambda). To increase confidence in the estimation of hemoglobin derivatives, the mathematical model was applied to only a part of the spectral function of reflectometry, while the results of the model were used to explain the other part of the reflectometry function. The results demonstrate that for the visible spectral field, the model that explains the absorption of the light by the blood contained in the microcapillaries of biological structures is not compatible with the Beer-Lambert law.