Effects of multiple-passage probabilities on fluorescent signals from biological media.

By applying a random-walk model for photon migration, we find an exact expression for fluorescent signals emitted from a homogeneous, optically turbid medium containing a single fluorescent mass. In contrast to diffusion-theory-based models, our analysis accounts for multiple photon passages through the fluorophore sites and allows for a variable degree of fluorescent absorptivity. We particularly discuss effects on the amplitudes and phase shifts of frequency-domain fluorescent signals.