<title>Image reconstruction in tissuelike turbid media under single and two-photon excitation</title>

Abstract

In this paper, we present the forward (optical gating) and inverse (reconstruction) approaches to obtain high-resolution imaging in tissue-like media under single-photon (1-p) and two-photon (2-p) excitation. Effective point spread functions (EPSF) for fluorescence microscopic imaging are introduced for fast image modeling and reconstruction. It is demonstrated that a deeper penetration depth can be achieved under 2-p excitation due to the use of a longer illumination wavelength and the non-linear dependence of the fluorescence on excitation intensity. The fundamental difference between 1-p and 2-p fluorescence imaging is that the penetration depth is limited by the degradation in image resolution in 1-p fluorescence, while the penetration depth is limited by the loss in signal strength in 2-p fluorescence imaging. Based on the EPSF that derived in the simulation, image reconstruction using deconvolution methods can partially recover the resolution loss.