Development and investigation of devices for ultrahigh speed gastrointestinal Optical Coherence Tomography imaging

Abstract

Diseases of the gastrointestinal (GI) tract are typically diagnosed by random biopsy of tissue, which samples only a small area and often misses focal neoplasias. Existing endoscopic visualization tools including white light endoscopy, narrowband imaging and confocal laser endomicroscopy have enabled in vivo assessment to guide biopsies, but suffer from technical limitations and have demonstrated suboptimal sensitivity and specificity to neoplasia. Optical Coherence Tomography (OCT) can generate in vivo, 3-dimensional microscopic imaging. Recent efforts in ultrahigh-speed OCT systems for endoscopic applications have shown promise, but devices had limited fields of view and imprecise beam scanning mechanisms, limiting image quality and coverage. This thesis develops a wide range of new fiber optic devices that substantially extend OCT capabilities in the GI tract, either by greatly increasing field of view for wide field mapping of entire luminal organs, or achieving high precision 2-D beam scanning with compact actuators for in vivo microscopy. Piezoelectrically actuated fiber scanning devices enable forward viewing for focal inspection, while micromotor actuators combined with pneumatic or piezoelectric mechanisms enclosed in tethered capsules generate side viewing over large areas. The work also advances the emerging paradigm of gastrointestinal screening without use of sedation, which promises to lower costs of screening and improve access for a broader population. Design, fabrication and benchtop evaluation of devices, as well as pre-clinical and clinical imaging protocols are reported. Results from validation studies in living swine, and human patients in collaboration with the Veterans Affairs Boston Healthcare System are discussed. The thesis work demonstrates new imaging modalities for in vivo detection and diagnosis of GI pathology that could have important applications in disease screening, surveillance, and therapeutic procedures.