Spatial distribution of single-photon and two-photon fluorescence light in scattering media: Monte Carlo simulation.
Three-dimensional fluorescence spatial distributions under single-photon and two-photon excitation within a turbid medium are studied with Monte Carlo simulation. It is demonstrated that two-photon excitation has an advantage of producing much less fluorescence light outside the focal region compared with single-photon excitation. With the increase of the concentration of scattering particles in a turbid medium, the position of the maximum fluorescence intensity point shifts from the geometric focal region toward the medium surface. Further studies show that the optical sectioning property of two-photon fluorescence microscopy is degraded in thick turbid media or when the numerical aperture of an objective becomes low.
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Optoelectronic Imaging Group, School of Communications and Informatics, Victoria University of Technology, PO Box 14428, Melbourne City Mail Centre, Victoria 8001, Australia.
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