EXPERIMENTAL-VERIFICATION OF A THEORY FOR THE TIME-RESOLVED FLUORESCENCE SPECTROSCOPY OF THICK TISSUES

Fluorescence spectroscopy provides potential contrast enhancement for near-infrared tissue imaging and physiologically correlated spectrosco py. We present a fluorescence photon migration model and test its quan titative predictive capabilities with a frequency-domain measurement t hat involves a homogeneous multiple-scattering tissue phantom (with op tical properties similar to those of tissue in the near infrared) that contains a fluorophore (rhodamine B). After demonstrating the validit y of the model, we explore its ability to recover the fluorophore's sp ectral properties from within the multiple-scattering medium. The abso lute quantum yield and the lifetime of the fluorophore are measured to within a few percent of the values measured independently in the abse nce of scattering. Both measurements are accomplished without the use of reference fluorophores. In addition, the model accurately predicts the fluorescence emission spectrum in the scattering medium. Implicati ons of these absolute measurements of lifetime, quantum yield, concent ration, and emission spectrum from within multiple-scattering media ar e discussed. (C) 1997 Optical Society of America