Optical coherence tomography (OCT) is a real-time high-resolution imaging technology providing cross-sectional images of biological structures at a resolution of <1 to 20 µm and a penetration depth of 1 to 3 mm in most highly scattering tissues. OCT is in general non-invasive and can perform real-time ‘optical biopsy’ with a resolution approaching standard low magnification histopathology but without tissue removal. Conventional OCT requires a bulky imaging probe, which limits most of the in vivo applications to ophthalmology and dermatology. The development of miniature OCT imaging probe has greatly expanded the scope of the applications (e.g., cardiology, gastroenterology, etc.). Recent technical advances in OCT has extended the imaging speed from a few kHz to a few hundreds kHz, enabling in vivo three-dimensional (3D) imaging.
This dissertation describes the development of a high-speed endoscopic OCT imaging system. The system employs the Fourier domain mode locking laser technology at a wavelength range of 1300 nm to reach an axial resolution of 9.7 µm and an A-scan rate of 220 kHz. A Mach-Zehnder interferometer setup is used to achieve shot-noise limited detection. A generic OCT software platform is developed for data acquisition, processing, display, storage, and 3D visualization. Miniature OCT imaging probes are designed and fabricated for in vivo 3D OCT imaging. The utility of the high-speed endoscopic OCT system is demonstrated for clinical and basic researches in pulmonology and gastroenterology. In addition, an ultrahigh-resolution endoscopic OCT system is developed at a wavelength range of 800 nm to reach an axial resolution of 3.0 µm and an A-scan rate of up to 20 kHz. Furthermore, a novel type of OCT contrast agents, scattering dominant gold nanocages, is developed with the aid of a cross-reference OCT imaging method. Finally, a multimodal endoscopic imaging system combines 1300 nm en face OCT and 1550 nm two photon fluorescence is developed.
Compared with most of other imaging modalities, high-speed endoscopic OCT has unmatched advantages including high spatial resolution, imaging speed, and non-invasiveness / minimal invasiveness. The results in this dissertation suggest that high-speed endoscopic OCT may has a great impact on healthcare as well as basic research
