Multiphoton tissue imaging using high-NA microendoscopes and flexible scan heads for clinical studies and small animal research.

Multiphoton tomographs based on femtosecond laser and GRIN lens technology in combination with flexible scan heads have been developed for clinical high-resolution tissue imaging and small animal research. The novel tissue tomograph possesses a 0.5 m long flexible mirror arm in combination with piezodriven focusing optics and multiple single photon counting PMT detectors. The photodetectors are in particular useful to obtain information on the extracellular matrix by the simultaneous measurement of the two-photon autofluorescence of elastin as well as the second harmonic generation of collagen. A major application is the in vivo determination of the skin age index. The rigid two-photon microendoscope with a high numerical aperture of 0.8 is based on a combination of silver-doped 1.0 mm rod-shaped GRIN lens with a hemispheric front optics. It was used in combination with the multiphoton tomograph for clinical studies as well as for inner organ and eye imaging of small animals.