PSFs in a two-photon excitation fluorescence microscope using different fiber delivery methods. The top figures show both the lateral and the axial PSF measurements with light delivered through various fibers. Free space delivery is included for comparison. Bottom figures represent statistical analysis of the lateral and the axial PSF FWHMs for each delivery method. The lateral resolution is dependent on the number of modes that the fiber supports, whereas the axial resolution is almost independent of delivery method. The symbol, *, on top of bars, indicates that optical resolution is statistically different from free space delivery, based on a t-test with P<0.05.