We compare the illumination uniformity and the associated effects of the spiral and Lissajous scanning patterns that are commonly used in an endomicroscope. Theoretical analyses and numerical simulations were first performed to quantitatively investigate the area illumination density in the spiral scanning pattern. The results revealed the potential problem of manifest photodamage due to the very high illumination density in the center of the spiral scan. Similar analyses of the Lissajous scanning pattern, which can be conveniently implemented on the same endomicroscope with no hardware modifications, showed a more uniform illumination density with about an 80-fold reduction in the peak illumination density. To underscore the benefit offered by the improved illumination uniformity, we conducted in vitro two-photon fluorescence imaging of cultured cells stained with a LIVE/DEAD viability assay using our home-built, fiber-optic, two-channel endomicroscopy system. Both the spiral and the Lissajous scans were implemented. Our experimental results showed that cells near the spiral scan center experienced obvious photodamage, whereas cells remained alive over the entire region under the Lissajous beam scanning, confirming the predicted advantage offered by the Lissajous scan over this spiral scan in an endomicroscopy setting.
This paper reviews our recent developments of ultrathin fiber-optic endomicroscopy technologies for transforming high-resolution
noninvasive optical imaging techniques to in vivo and clinical applications such as early disease detection and guidance of
interventions. Specifically we describe an all-fiber-optic scanning endomicroscopy technology, which miniaturizes a conventional
bench-top scanning laser microscope down to a flexible fiber-optic probe of a small footprint (i.e. ~2-2.5 mm in diameter), capable of
performing two-photon fluorescence and second harmonic generation microscopy in real time. This technology aims to enable realtime
visualization of histology in situ without the need for tissue removal. We will also present a balloon OCT endoscopy technology
which permits high-resolution 3D imaging of the entire esophagus for detection of neoplasia, guidance of biopsy and assessment of
therapeutic outcome. In addition we will discuss the development of functional polymeric fluorescent nanocapsules, which use only
FAD approved materials and potentially enable fast track clinical translation of optical molecular imaging and targeted therapy.