Browsing by Subject "Optical coherence tomography"
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Item 3D image processing and FPGA implementation for optical coherence tomography(2013-08) Carroll, Sylvia D; Milner, Thomas E.This thesis discusses certain aspects of the noninvasive imaging technique known as optical coherence tomography (OCT). Topics include three-dimensional image rendering as well as application of the Fast Fourier Transform to reconstruct the axial scan as a function of depth. Implementations use LabVIEW system design software and a Xilinx Spartan-6 field-programmable gate array (FPGA). The inherent parallel-processing capability of an FPGA opens the possibility of designing a "super-sensor" which entails simultaneous capturing of image and sensor data, giving medical practitioners more data for potentially improved diagnosis. FPGA-based processing would benefit many methods of characterizing biological samples; OCT and photonic crystal microarray biosensors are discussed.Item Design and implementation of a miniaturized swept source spectral domain polarization sensitive optical coherence tomographic imaging system to diagnose glaucoma(2010-05) Asokan, Nitin; Rylander, H. Grady (Henry Grady), 1948-; Milner, Thomas E.Glaucoma is an ophthalmic pathology that is the second leading cause of blindness. The laboratory design of a Polarization Sensitive Spectral Domain Optical Coherence Tomographic System aims to detect early glaucoma symptoms and prevent vision loss that occurs due to late or no glaucoma diagnosis. In order to perform human clinical trials at partner hospitals across the country, a miniaturized and portable version of the laboratory system was developed. The system facilitates easy transportation and clinical testing of the otherwise voluminous laboratory system across different eye centers. Significant consideration was given for performance optimization, cost reduction, design improvements and providing a friendly user-patient interface.Item Development and application of optical imaging techniques in diagnosing cardiovascular disease(2012-05) Wang, Tianyi, 1982-; Milner, Thomas E.; Feldman, Marc; Johnston, Keith; Dunn, Andrew; Tunnell, JamesAtherosclerosis and specifically rupture of vulnerable plaques account for 23% of all deaths worldwide, far surpassing both infectious diseases and cancer. Plaque-based macrophages, often associated with lipid deposits, contribute to atherogenesis from initiation through progression, plaque rupture and ultimately, thrombosis. Therefore, the macrophage is an important early cellular marker related to vulnerability of atherosclerotic plaques. The objective of my research is to assess the ability of multiple optical imaging modalities to detect, and further characterize the distribution of macrophages (having taken up plasmonic gold nanoparticles as a contrast agent) and lipid deposits in atherosclerotic plaques. Tissue phantoms and macrophage cell cultures were used to investigate the capability of nanorose as an imaging contrast agent to target macrophages. Ex vivo aorta segments from a rabbit model of atherosclerosis after intravenous nanorose injection were imaged by optical coherence tomography (OCT), photothermal imaging (PTW) and two-photon luminescence microscopy (TPLM), respectively. OCT images depicted detailed surface structure of atherosclerotic plaques. PTW images identified nanorose-loaded macrophages (confirmed by co-registration of a TPLM image and corresponding RAM-11 stain on a histological section) associated with lipid deposits at multiple depths. TPLM images showed three-dimensional distribution of nanorose-loaded macrophages with a high spatial resolution. Imaging results suggest that superficial nanorose-loaded macrophages are distributed at shoulders on the upstream side of atherosclerotic plaques at the edges of lipid deposits. Combination of OCT with PTW or TPLM can simultaneously reveal plaque structure and composition, permitting assessment of plaque vulnerability during cardiovascular interventions.Item High resolution retinal imaging to evaluate laser and light safety in the retina for near and long term health effects(2012-12) Pocock, Ginger Madeleine; Snodderly, D. Max; Rylander, H. Grady (Henry Grady), 1948-; Markey, Mia K.; Milner, Tom E.; Oliver, Jeffrey W.The purpose of this research was to investigate detect and monitor laser-tissue interactions at threshold and potentially sub-threshold levels of injury. High resolution imaging modalities can provide a deeper understanding of candidate biomarkers disease and injury at the molecular, cellular, and tissue-levels which can be used to identify and diagnose early stages disease and damage. In addition, multi-scale and multi-modal imaging have also been used to identify inherent biomarkers of retinal disease and injury. Monitoring tissue changes can be mapped back to biological changes at the cellular and sub-cellular level. Diseases often alter tissue on the ultra-structural level yet retinal clinical diagnosis often monitor changes in tissue at the organ level. If injury and disease is detected and diagnosed during an “early” stage of development, treatments and drug interventions may prevent further spread of the pathology. Non-invasive imaging is expected to be a valuable tool for in vivo medical research as well as for the diagnosis and management of disease. In addition to developing new imaging tools and techniques to image the retina, the identification of inherent biomarkers of disease and health using diagnostic methods are almost equally as important. Using the inherent optical properties of retinal tissue, we can non- invasively quantify differences in the absorption and reflection of light to gauge the risk for visual disability or worse yet irreversible vision loss as a result of retinal disease and chronic light exposure. The research presented with in this dissertation is three separate studies aimed at identifying light injury and potential biomarkers indicating the risk of light mediated development of disease.Item Optical coherence tomography for retinal diagnostics(2013-08) Yin, Biwei; Milner, Thomas E.; Rylander, H. Grady (Henry Grady), 1948-Optical Coherence Tomography (OCT) is a non-invasive three-dimensional imaging technique. OCT synthesizes a cross-sectional image from a series of lateral adjacent depth scans, and with a two-dimensional scanning scheme, three-dimensional intensity image of sample can be constructed. Due to its non-invasive capability, OCT has been widely applied in ophthalmology, cardiology and dermatology; and in addition to three-dimensional intensity image construction, various functional OCT imaging techniques have been developed for clinical application. My research is focused on developing functional OCT systems for application in ophthalmology, including polarization-sensitive optical coherence tomography (PS-OCT) for retinal nerve fiber layer (RNFL) birefringence measurement and dual-wavelength photothermal optical coherence tomography (DWP-OCT) for microvasculature blood oxygen saturation (SO2) measurement. In the study, a single-mode-fiber based polarization-sensitive swept-source OCT (PS-SS-OCT) with polarization modulator, polarization-sensitive bulk-optics balanced detection module is constructed and polarization processing methods based on Stokes vectors are applied to determine birefringence. PS-OCT is able to provide human subject's RNFL thickness, phase retardation, and birefringence information. Degradation in the degree of polarization (DOP) along depth is investigated and its difference between four quadrants of RNFL (superior, temporal, inferior and nasal) indicates the structural property difference. DWP-OCT is a novel functional OCT system consisting of a phase-sensitive optical coherence tomography system (PhS-OCT) and two photothermal excitation lasers. PhS-OCT is based on a swept-source laser operating in the 1060 nm wavelength range; the two photothermal excitation lasers with wavelength 770 nm and 800 nm are intensity modulated at different frequencies. PhS-OCT probe beam and two photothermal excitation beams are combined and incident on the sample, optical pathlength (op) change on the sample introduced by two photothermal excitation beams are measured and used for blood SO2 estimation. A polarization microscope is proposed for future study. The polarization microscope is an imaging technique providing molecular structure and orientation based on probe light's polarization state information. The polarization microscope uses a wavelength tunable light source, and can achieve any incident polarization state by a retarder-rotator combination. Specimen's birefringence can be determined based on the changing of detected light amplitude.Item Optical designs and image processing algorithms for optical coherence tomography detection of glaucoma(2014-08) Wang, Bingqing; Rylander, H. Grady (Henry Grady), 1948-; Milner, Thomas E.; Tunnell, James W.; Dunn, Andrew K.; Bovik, Alan C.Optical Coherence Tomography (OCT) is an optical tomography technique which provides high resolution non-invasive three-dimensional (3D) structural images of the sample based on coherent properties of light. The dissertation focuses on the use of OCT systems for detecting glaucoma, which is the second leading cause of blindness worldwide. First, as a prerequisite of analyzing ophthalmologic OCT images, a retinal sublayer segmentation algorithm is presented and implemented with GPU assisted computation. Then, a polarization-sensitive optical coherence tomography (PS-OCT) system was constructed for the study of glaucoma. Three closely related clinical and animal studies on early-stage glaucoma detection using either OCT or PS-OCT were performed. Statistical analysis of the study results indicates that the scattering property of retinal nerve fiber layer (RNFL) is the earliest indicator for glaucoma. Finally, to investigate the scattering properties of RNFL, a pathlength-multiplexed scattering-angle-diverse optical coherence tomography (PM-SAD-OCT) system was designed and built. PM-SAD-OCT images were collected from human and rodent retina as well as earthworm nerve cord. PM-SAD-OCT system shows promising potentials to detect neurodegenerative diseases including glaucoma.Item Polarimetric analysis of anisotropic tissue using polarization-sensitive optical coherence tomography (PS-OCT)(2006) Park, Jesung; Rylander, H. Grady, III; Milner, Thomas E.Item Polarization sensitive optical coherence tomography for primate retinal evaluation in a longitudinal glaucoma study(2011-12) Dwelle, Jordan Charles; Rylander, H. Grady (Henry Grady), 1948-; Milner, Thomas E.A polarization sensitive optical coherence tomography (PS-OCT) instrument is presented for the study of glaucoma. Glaucoma is the second leading cause of blindness worldwide and causes irreversible damage to the retina. This PS-OCT system was built to perform retinal imaging with a swept source laser providing a 28 kHz A-scan repetition rate. Thickness, phase retardation, birefringence and reflectance index measurements were taken from the primate eyes on a weekly or semi-weekly basis through the course of a 30 week study. Statistical analysis of these measurements indicates that the reflectance index is the earliest measured indicator of glaucomatous changes and a potential marker for early glaucoma diagnosis.Item Thickness, phase retardation, birefringence, and reflectance of the retinal nerve fiber layer : implications for glaucoma diagnosis(2012-05) Liu, Shuang, active 2012; Rylander, H. Grady (Henry Grady), 1948-; Markey, Mia KathleenGlaucoma is the second leading cause of blindness worldwide after cataract. Retinal nerve fiber layer thickness (RNFLT), phase retardation, and birefringence measured by Polarization Sensitive Optical Coherence Tomography (PS-OCT) have been used for glaucoma diagnosis. We first investigated two different image registration algorithms, a mutual information (MI) based algorithm and a log-polar transform cross-correlation (LPCC) based algorithm, on both human and non-human primate models. We evaluated the effects of image registration on longitudinal analysis of RNFLT in non-human primates using PS-OCT. Then, we investigated thickness, phase retardation, birefringence, and reflectance of the retinal nerve fiber layer as measured by PS-OCT in normal and glaucomatous non-human primates in a longitudinal study. We defined a new Reflectance Index (RI) and demonstrated that it might be an earlier indicator of glaucoma onset than RNFLT, phase retardation, or birefringence. Finally, we validated this finding on cross-sectional clinical study on human eyes measured by PS-OCT and RTVue OCT. For the data measured by PS-OCT, we showed that for distinguishing between glaucomatous and healthy eyes, as well as for distinguishing between glaucoma suspect and healthy eyes, our new normalized RNFL reflectance index (NRRI) performs significantly better than phase retardation and birefringence. The performances of NRRI and RNFL thickness in both conditions were statistically indistinguishable in this study, which is likely due to the limited sample size. For the data measured by RTVue OCT, the performances of NRRI and RNFL thickness were statistically indistinguishable for distinguishing between glaucomatous and healthy eyes. NRRI performs significantly better than RNFL thickness for distinguishing between glaucoma suspect and healthy eyes. NRRI also performs significantly better than temporal, superior, nasal, inferior and temporal (TSNIT) average and nerve fiber indicator (NFI) from GDx VCC for distinguishing between glaucoma suspect and healthy eyes. NRRI is a promising parameter for distinguishing glaucoma suspect and healthy eyes and may indicate disease in the pre-perimetric stage.