Analytical model of fluorescence intensity for the estimation of fluorophore localisation in biotissue with dual-wavelength fluorescence imaging

Analytical expression for the fluorescence response of a photosensitiser uniformly distributed in the superficial layer of biotissue is obtained in the diffusion approximation of radiative transfer theory, and the approach for estimating the fluorescent layer thickness based on dual-wavelength excitation of fluorescence is proposed. It is shown that the error in estimation of the fluorescent layer thickness employing the ratio of the fluorescence signals obtained at different excitation wavelengths does not exceed 30% for the thickness range of 0.1-2 mm in the case of 30%-variation of biotissue optical properties.