Two-photon fluorescence imaging of microspheres embedded in turbid media

Fluorescent microspheres of diameter 10μm embedded in a turbid medium consisting of polystyrene beads suspended in water are imaged under two-photon and single-photon excitation. A comparison of two-photon and single-photon fluorescence images shows that multiple scattering leads to a dominant limiting factor of the signal-to-noise ratio in the former case, while it results in a dominant limiting factor of resolution in the latter case. These results are qualitatively consistent with the predication by the Monte-Carlo simulation based on Mie scattering theory