Optical coherence tomography (OCT) is a light based interferometric imaging technique that can provide high resolution (5-20 µm at 1300 nm), depth resolved, images in real-time. With recent advances in portable low coherent light sources for OCT it is now possible to achieve ultrahigh axial resolutions (≤ 3 µm) by moving to shorter central wavelengths such as 800 nm while utilizing a broad spectral bandwidth. Our goal was to push ultrahigh resolution OCT technology to in vivo imaging of internal organs for endoscopic assessment of tissue microstructure. This dissertation is separated into technological developments and biomedical imaging studies.
Technological developments in this dissertation included development of a high speed, ultrahigh resolution distal scanning catheter. This catheter was based upon a miniature DC micromotor capable of rotational velocities in excess of 100 rps, a diffractive compound lens design that minimized chromatic aberrations, and a mechanical assembly that limited field of view blockage to less than 7.5% and maintained an outer diameter of 1.78 mm (with plastic sheath). In conjunction with the algorithm described in chapter 4 to correct for non-uniform rotational distortion, the overall imaging system was capable of high quality endoscopic imaging of internal organs in vivo.
Equipped with the ultrahigh resolution endoscopic OCT system, imaging was performed in small airways and colorectal cancer. Imaging results demonstrated the ability to directly visualization of microstructural details such as airway smooth muscle in the small airways representing a major step forward in pulmonary imaging. With the ability to visualize airway smooth muscle, morphological changes in COPD and related diseases can be further investigated. Additionally, longitudinal changes in an ETBF induced colon cancer model in APCMin mice were studied as well. Quantitative assessment of tissue microarchitecture was performed by measuring the attenuation coefficient to find a bimodal distribution separating normal healthy tissue from polyps.
Finally, results from two additional projects were also demonstrated. Chapter 7 shows some results from vascular imaging in a tumor angiogenesis model and middle cerebral artery occlusion model. Chapter 8 describes an endoscopic multimodal OCT and fluorescence imaging platform with results in ex vivo rabbit esophagus
