UC Irvine

In recent years researchers have made significant progress in understanding the physics of fluorescence in highly scattering materials such as tissues in the near-infrared. We have quantitatively verified a model which describes fluorescence in ideal (homogeneous and infinite) tissue-like media. Given the quantitative accuracy of this model, one can use measurements of the fluorescence of a tissue with a homogeneous distribution of fluorophore to obtain the quantum yield, lifetime of the probe, and the absorption and scattering coefficients of the tissue at the fluorescent wavelength. We demonstrate that this can be done with a simple measurement of the photon density as a function of source-detector separation at the excitation and emission wavelengths. To verify our approach we present the lifetime, quantum yield of the fluorescent probe (rhodamine B), and the absorption and scattering coefficients of the medium at the emission peak wavelength that are obtained by a fit of the model to experimental measurements.