In recent years, the importance of blood flow distribution has been highlighted in a wide range of diseases that involve the cerebral microvasculature. Specifically, microvascular heterogeneity, related to the non-uniform distribution of blood flow through the microvasculature, is an important parameter that is critical to the efficacy of oxygen extraction. As increased heterogeneity may lead to oxygen insufficiency, even with blood flow above ischemic levels, heterogeneity may be an important biomarker for understanding disease progression. However, current methods of quantifying microvascular heterogeneity over large microvascular networks that extend deep into biological tissue (such as the cerebral cortical microvasculature) are limited ...

Colorectal cancer (CRC) remains the second deadliest cancer in the United States, despite steady reduction in mortality rate over the last three decades. Colonoscopy is the gold-standard screening modality with high sensitivity and specificity to mature polyps. However, the miss rate for small (< 5 mm) lesions is estimated to be as high as 26%. Because the five-year survival rate for CRC detected at the local stage is 90%, there is a clear need for a screening procedure that is sensitive to these small lesions. Optical coherence tomography (OCT) has become a major biomedical imaging modality since its invention in 1991 ...

Recent advances in Optical Coherence Tomography (OCT) have enabled wide ranges of attractive applications, including characterization of biological tissues, morphological tracking, intravascular imaging, developmental biology and in functional spectroscopic aspects. Neural activity has been studied using optical methods in the past few decades. The use of light to probe neural activity allows outstanding resolution, and the possibility for simultaneous measurement from a range of targeted locations without physical contact with the tissue. Optically detectable signals, such as transient changes with phase and backscattered light intensity, are captured using spectral-domain OCT system. In this dissertation, a fundamental introduction to polarizationmaintaining fiber-based ...

The human eye is an organ that detects light from the environment and translates it into vision with the help of the brain. Eye health is critical to our daily life, such as working, reading, driving, sporting, and communicating with people. Malfunction of the eye can cause eye discomfort and clinical depressions, impair the patients’ independence, and compromise quality of life. For this reason, there is a broad range of interests in the field of eye research for better understanding of the eye that could help in early diagnosis and treatment of the prevalence eye diseases and benefit an increasing ...

Ophthalmic microsurgery is one of the most commonly performed surgical procedures in the world and it necessitates precise three-dimensional manipulation of tissue at submillimeter spatial scales. As a result, ophthalmic surgeons require an operating microscope to perform surgery and to asses alterations to the tissue. Unfortunately, modern operating microscopes provide a limited en face perspective of the three-dimensional surgical field, and surgeons must infer depth information using stereoscopy and cannot directly visualize subsurface anatomy. These limitations may compromise the surgeon’s ability to maneuver instruments axially and to comprehensively evaluate the three-dimensional tissue structure. Optical coherence tomography (OCT) is a ...

Over the past two decades, optical coherence tomography (OCT) has been successfully applied to various fields of biomedical researching and clinical studies, including cardiology, urology, dermatology, dentistry, oncology, and most successfully, ophthalmology. This dissertation seeks to extend the current OCT practice, which is still largely morphology-based, into a new dimension, functional analysis of metabolic activities in vivo. More specifically, the investigation is focused on retrieving blood oxygen saturation (sO2) using intrinsic hemoglobin optical absorption contrast. Most mammalian cells rely on aerobic respiration to support cellular function, which means they consume oxygen to create adenosine triphosphate (ATP). Metabolic rate of oxygen ...

Human vision starts when photoreceptors collect and respond to light. Photoreceptors do not function in isolation though, but share close interdependence with neighboring photoreceptors and underlying retinal pigment epithelium (RPE) cells. These cellular interactions are essential for normal function of the photoreceptor-RPE complex, but methods to assess these in the living human eye are limited. One approach that has gained increased promise is highresolution retinal imaging that has undergone tremendous technological advances over the last two decades to probe the living retina at the cellular level. Pivotal in these advances has been adaptive optics (AO) and optical coherence tomography (OCT ...

Optical Coherence Tomography (OCT) is an imaging tool that performs micronresolution, non-invasive, cross-sectional imaging by measuring the echoes of backscattered light. In this thesis, a custom-designed polarization-sensitive OCT (PS-OCT) system is discussed, which is implemented in using plasmonic gold nanorods (GNRs) as diffusion probes. PS-OCT imaging is undertaken in Newtonian fluids and validation of rotational and translational diffusion of GNRs with the Stokes-Einstein relation is presented via analysis of the autocorrelations of the OCT signals. Diffusion of GNRs in non-Newtonian fluids is also studied and the frequency-dependent viscoelasticity is also explored using generalized Stokes-Einstein relation. Furthermore, diffusion of GNRs in ...

Fourier domain optical coherence tomography (FD-OCT) is a high-speed, highresolution, and noninvasive imaging technique that can obtain cross-sectional images of light scattering medium, such as biomedical tissues. In this thesis, I report three novel methods in FD-OCT technique including common-path endoscopic FD-OCT, streakmode FD-OCT, and Doppler streak-mode FD-OCT. Finally, I apply the streak mode FDOCT to ultrahigh-speed, noninvasive, live imaging of embryonic chick hearts. An extension of conventional FD-OCT technique is endoscopic FD-OCT, which can access internal organs by utilizing a miniaturized catheter design. However, its image signal suffers from the bending of the endoscopic catheter. To address this problem ...