Point spread function measured in human skin using two-photon fluorescence microscopy

Abstract

The two-photon excitation point spread function (TPE-PSF) has been measured in human skin in vitro in order to examine the optical resolution. This has been done by injecting fluorescent subresolution beads in skin samples using a syringe. The beads were imaged at different depths and the full width at half maximum (FWHM) of the TPE-PSF in the lateral and axial direction were measured from the intensity profile of the emission. The experimentally obtained values of the PSF widths were larger than calculated values. Both the lateral FWHM and the axial FWHM were broadened as a function of depth but the increase was stronger in the axial direction. This indicates that the optical properties of the skin have a more pronounced effect of the resolution in the axial direction.