Two-color fluorescence excitation confocal-theta imaging in highly-scattering media

Abstract

The need for ever-increasing imaging resolution to study intracellular structures hidden underneath skin layers has provided the impetus for developing various optical methods to image through scattering media. Time-gating techniques that reject stray photons in the temporal domain achieve sub-millimeter accuracy. Using spatial filtering techniques, this limit was breached and pushed to micron resolution by confocal optical systems and then beyond using two-photon fluorescence microscopy, attaining sub-micron sampling.
In this paper, we propose an optical system to increase the imaging resolution further by merging the excellent optical qualities of two existing detection schemes: confocal-theta microscopy and two-photon fluorescence excitation. A Monte Carlo (MC) simulation platform is then utilized to model the excitation, fluorescence and detection processes for scattering media of different thickness and particle size.