1. Articles in category: Student Theses

    193-216 of 270 « 1 2 ... 6 7 8 9 10 11 12 »
    1. Development of functional near-infrared optical coherence tomography (Thesis)

      Development of functional near-infrared optical coherence tomography (Thesis)

      Medical imaging is a discipline where the fields of mathematics, physics, biology, and medicine are combined in the acquisition, computation and interpretation of threedimensional images of (human) tissue. A variety of imaging modalities that provide information about morphological structure and function of biological tissues has been developed. These modalities are based on electromagnetic waves (magnetic resonance imaging, X-ray computed tomography, confocal microscopy), sound (ultrasonography), or nuclear tracers (positron emission tomography, single photon emission computed tomography). In the last decades, these medical imaging modalities have become a key tool in disease diagnosis, treatment monitoring, and disease prevention. Compared to other imaging ...

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    2. Polarization Sensitive Optical Coherence Tomography for Primate Retinal Evaluation in a Longitudinal Glaucoma Study

      Polarization Sensitive Optical Coherence Tomography for Primate Retinal Evaluation in a Longitudinal Glaucoma Study

      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 ...

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    3. Retrograde trans-synaptic retinal ganglion cell loss following retrogeniculate lesions of human visual pathway identified using optical coherence tomography (Thesis)

      Retrograde trans-synaptic retinal ganglion cell loss following retrogeniculate lesions of human visual pathway identified using optical coherence tomography (Thesis)
      Retrograde trans-synaptic degeneration (RTSD) in the human visual pathway has not been well clarified. Aims 1. To confirm the RTSD in human visual pathway. 2. To study the rate of RTSD. 3. To study the pupil function in the RTSD. Methods: 1. The peripapillary retinal nerve fibre layer (RNFL) thickness measured with optical coherence tomography was compared among patients with acquired and congenital retrogeniculate lesions and normal subjects. Humphrey perimetry and brain imaging were performed. 2. A relationship between the duration of the disease and the RNFL thickness measured at a single time point was evaluated. Additionally the RNFL thickness ...
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    4. Measurement of retinal vascular permeability in a rat model using spectroscopic optical coherence tomography

      Measurement of retinal vascular permeability in a rat model using spectroscopic optical coherence tomography

      Optical coherence tomography (OCT), a diagnostic tool which can perform non-contact, noninvasive, cross-sectional imaging of the retina and anterior eye in real time, has dramatically improved in its resolution and speed in the recent years. In addition to the advancement in hardware, different OCT methods for functional measurements, such as Doppler OCT for quantifying blood flow and generating angiography using OCT phase information, polarization sensitive OCT for measuring intrinsic mechanical / optical tissue property using light of different polarizations, and spectroscopic OCT for measuring blood oxygenation using multiple wavelengths, have been demonstrated and developed. In this thesis, a dual-wavelength spectroscopic OCT ...

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    5. Interferometric Synthetic Aperture Microscopy (ISAM) Reconstruction and Characterization In A High Numerical Aperture System (Thesis)

      Interferometric Synthetic Aperture Microscopy (ISAM) Reconstruction and Characterization In A High Numerical Aperture System (Thesis)
      Optical coherence microscopy (OCM) is an imaging modality that is capable of visualizing structural features of biological samples at high resolution based on their scattering properties. Interferometric synthetic aperture microscopy (ISAM) is a newer technique that can overcome the typical dependence between lateral resolution and depth-of-focus of an optical coherence tomography (OCT) imaging system by offering spatially invariant resolution within the whole 3D data set, including regions that are outside of the focal region. Both OCM and ISAM have many potential research and clinical applications. By combining OCM and ISAM, it is possible to visualize an entire 3D volumetric data ...
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    6. 3-D Volumetric Optical Coherence Tomography Imaging and Image Analysis of Barrett's Esophagus (Thesis)

      3-D Volumetric Optical Coherence Tomography Imaging and Image Analysis of Barrett's Esophagus (Thesis)
      Barrett's esophagus (BE) surveillance remains challenging, because even histopathology, the gold standard, is subject to sampling error. The esophageal mucosal area involved in BE can be 20 square centimeters or more. 3-D volumetric Imaging technology with high diagnostic accuracy may potentially guide and assist the standard histopathology, eliminate the sampling error and improve surveillance efficiency. It has been shown that endoscopic optical coherence tomography (EOCT) of a small mucosal area can obtain interpretable images of gastro-intestinal mucosal microstructure, differentiate mucosal types and detect dysplasia in Barrett’s esophagus. The realization of 3-D EOCT allows for further exploring the potential ...
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    7. A Study of Spectral Domain Optical Coherence Tomography and Photoacoustic Microscopy for Biometric and Biomedical Applications (Thesis)

      A Study of Spectral Domain Optical Coherence Tomography and Photoacoustic Microscopy for Biometric and Biomedical Applications (Thesis)
      Optical coherence tomography (OCT) has been widely used in biomedical imaging ever since its introduction. However, the application of OCT for biometrics is relatively new. This thesis demonstrates the feasibility of applying a spectral domain optical coherence tomography (SD-OCT) system to fingertip biometric information retrieval. The results show that SD-OCT is capable of retrieving Level 3 fingertip information. Combined with traditional Level 1 and 2 fingerprint information, which can also be easily acquired by SD-OCT, the proposed application shows potential for ultra-secure scenarios. Photoacoustic microscopy (PAM) is another imaging modality gaining considerable interest in the past decade. Different than OCT ...
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    8. Development Of Fourier Domain Optical Coherence Tomography A Dissertation ...

      Development Of Fourier Domain Optical Coherence Tomography A Dissertation ...

      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 ...

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    9. Directional property of the retinal reflection measured with optical coherence tomography and wavefront sensing (Thesis)

      Directional property of the retinal reflection measured with optical coherence tomography and wavefront sensing (Thesis)
      The last thirty years have experienced tremendous advancement in our understanding of light-tissue interactions in the human retina. Nevertheless, major gaps remain, and our modeling of light return from the back of the eye continues to evolve. The objective of this thesis is to investigate one of these gaps, specifically that related to the directional property (angular dependence) of the retinal reflection and in particular that of cone photoreceptors. Directionality of cones is commonly referred to as the optical Stiles-Crawford effect (SCE). While cone directionality is well known to originate from their waveguide properties, considerable uncertainty remains as to which ...
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    10. Characterization of Cardiac Tissue Using Optical Coherence Tomography (Thesis)

      Characterization of Cardiac Tissue Using Optical Coherence Tomography (Thesis)
      Radiofrequency ablation (RFA) therapy is the standard of care for the treatment of cardiac arrhythmias. Current techniques to guide ablation therapy utilize low resolution two dimensional fluoroscopic images and functional measurements from the RFA catheter, temperature, impedance and electrograms. High resolution, depth resolved imaging is needed to characterize early structural changes in the myocardium due to disease and therapy. Optical coherence tomography (OCT) is a noninvasive imaging modality that provides high resolution, depth resolved imaging of tissue microstructure in real time. OCT provides subsurface imaging of depths 1-2 mm in cardiac tissue with high spatial resolution (~10 μm) in three ...
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    11. Measuring Optical Properties of Engineered Tissues Using Optical Coherence Tomography (Thesis)

      Measuring Optical Properties of Engineered Tissues Using Optical Coherence Tomography (Thesis)
      The ability of optical imaging techniques such as optical coherence tomography (OCT) to non-destructively characterize engineered tissues has generated enormous interest recently. The engineered tissue of interest here is the collagen gel, wherein smooth muscle cells (SMCs) are embedded in a 3D collagen I matrix. This thesis focuses on characterizing collagen gels quantitatively, by measuring the optical properties – the scattering coefficient s and anisotropy factor g – from OCT data by fitting the signal to a theoretical model. μ[subscript s] and g are macroscopic physical properties that provide information on the density and size of scattering particles in the sample ...
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    12. An optical smart needle : point-of-care technologies for integrated needle guidance using optical frequency domain ranging (Thesis)

      An optical smart needle : point-of-care technologies for integrated needle guidance using optical frequency domain ranging (Thesis)
      Obtaining accurate needle placement is of critical importance in many medical scenarios. In the setting of fine needle aspiration biopsy (FNAB), manual palpation is often the only cue for determining the optimal position of the needle. As a result, FNAB procedures frequently yield non-diagnostic tissue. When not guided by an imaging modality, breast and thyroid FNAB's only obtain diagnostic tissue in approximately 65% of cases. Although the addition of noninvasive imaging technology has been shown to increase FNAB yield, it is time-consuming, relatively expensive, and often requires additional personnel with specialized expertise. A need exists for low-cost, small, simple ...
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    13. Validation of Optical Coherence Tomography-Based Crystalline Lens Thickness Measurements in Children (Thesis)

      Validation of Optical Coherence Tomography-Based Crystalline Lens Thickness Measurements in Children (Thesis)
      The purpose of this study was to evaluate the validity and repeatability of crystalline lens thickness measurements obtained by anterior segment optical coherence tomography (OCT). Optical coherence tomography utilizes infrared light and partial-coherence interferometry to produce a two-dimensional scan of the internal ocular structures in vivo. Changes in crystalline lens thickness are important to monitor for refractive error development, cataract progression, and anterior chamber alterations. Our goal was to develop an effective method of measuring the thickness of the crystalline lens with the Visante anterior segment OCT, to assess OCT repeatability, and to evaluate OCT validity as compared to A-scan ...
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    14. Anterior Segment Optical Coherence Tomography-Based Phakometry Measurements in Children (Thesis)

      Anterior Segment Optical Coherence Tomography-Based Phakometry Measurements in Children (Thesis)
      Anterior segment optical coherence tomography (AS-OCT) is emerging as a valuable tool for in vivo ocular biometry. This study constitutes the first known attempt at in vivo assessment of crystalline lens curvature using AS-OCT technology. METHODS: An ASOCT phakometry protocol was compared to video-based phakometry data on a sample of 42 children. RESULTS: AS-OCT phakometry demonstrated poor 95% limits of agreement (LOA) and significant magnitude bias, yielding excessively flat radii when used to measure flatter surfaces (anterior: P < 0.001, LOA = -8.82 to +6.52 mm; posterior: P < 0.001, LOA = -1.13 to +1.67 mm). Orthogonal regression-derived ...
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    15. Applications of Fourier Domain Mode Locked lasers for optical coherence tomography imaging (Thesis)

      Applications of Fourier Domain Mode Locked lasers for optical coherence tomography imaging (Thesis)
      Optical coherence tomography (OCT) is a micrometer-resolution imaging technique that produces cross-sectional images of sample microstructure by measuring the amplitude and echo time delay of backscattered light. OCT imaging is performed using low-coherence interferometry, typically with a fiber optic Michelson interferometer. OCT imaging has recently been performed by measuring the spectrum of the interference signal in the Fourier domain. In "swept source OCT" implementations, the interference spectra are generated with a wavelength-swept laser and photodetector. Axial image lines are obtained via Fourier transformation of the spectra. Fourier domain techniques have extended OCT imaging speeds from several thousand to hundreds of ...
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    16. The Use of Intracoronary Optical Coherence Tomography in Interventional Cardiology: Safety, Feasibility and Clinical Applications (Thesis)

      The Use of Intracoronary Optical Coherence Tomography in Interventional Cardiology: Safety, Feasibility and Clinical Applications (Thesis)
      Interventional cardiology has witnessed tremendous change since 1977 when Andreas Gruentzig successfully performed the first balloon angioplasty. Whereas initial concerns revolved around maintaining vessel patency with issues of recoil and restenosis, the introduction of stents changed the landscape forever. Inherent with their use, stents, and, more specifically, drugeluting stents (DES), have become central to improved patient outcomes but, at some cost. Catastrophic, yet fortunately still rare complications such as stent thrombosis have re-ignited an intense need for greater scrutiny when developing and, subsequently implanting DES into our patients. The demand for detailed information regarding coronary artery disease has seen intravascular ...
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    17. Image analysis of Optical Coherence Tomography images of the urinary bladder for the recognition of bladder cancer (Thesis)

      Image analysis of Optical Coherence Tomography images of the urinary bladder for the recognition of bladder cancer (Thesis)
      The vast majority of bladder cancers originate within 600 mum of the tissue surface, making Optical Coherence Tomography (OCT) a potentially powerful tool for recognizing cancers that are not easily visible with current techniques. OCT is a new technology, however, and surgeons are not familiar with the resulting images. Technology able to analyze and provide diagnoses based on OCT images would improve the clinical utility of OCT systems. In addition, to avoid the need for gathering training data sets each time a new OCT system is used, it is important that the technology developed be system-independent. In this dissertation, I ...
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    18. Optical Imaging Modalities: From Design to Diagnosis of Skin Cancer (Thesis)

      Optical Imaging Modalities: From Design to Diagnosis of Skin Cancer (Thesis)
      This study investigates three high resolution optical imaging modalities to better detect and diagnose skin cancer. The ideal high resolution optical imaging system can visualize pre-malignant tissue growth non-invasively with resolution comparable to histology. I examined 3 modalities which approached this goal. The first method examined was high magnification microscopy of thin stained tissue sections, together with a statistical analysis of nuclear chromatin patterns termed Karyometry. This method has subcellular resolution, but it necessitates taking a biopsy at the desired tissue site and imaging the tissue ex-vivo. My part of this study was to develop an automated nuclear segmentation algorithm ...
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    19. Functional Spectral Domain Optical Coherence Tomography Imaging (Thesis)

      Functional Spectral Domain Optical Coherence Tomography Imaging (Thesis)
      Spectral Domain Optical Coherence Tomography (SDOCT) is a high-speed, high resolution imaging modality capable of structural and functional resolution of tissue microstructure. SDOCT fills a niche between histology and ultrasound imaging, providing non-contact, non-invasive backscattering amplitude and phase from a sample. Due to the translucent nature of the tissue, ophthalmic imaging is an ideal space for SDOCT imaging. Structural imaging of the retina has provided new insights into ophthalmic disease. The phase component of SDOCT images remains largely underexplored, though. While Doppler SDOCT has been explored in a research setting, it remains to catch on in the clinic. Other, functional ...
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    20. Coherence domain optical imaging techniques (Thesis)

      Coherence domain optical imaging techniques (Thesis)
      Coherence domain optical imaging techniques have been developing quickly in the past few decades after the invention of laser. In this thesis, I will report the imaging methods that constitute my research projects during these years of graduate studies, including paired-angle-rotation scanning (PARS) forward-imaging probe for optical coherence tomography (OCT), full-field phase imaging technique based on harmonically matched diffraction grating (G1G2 grating), and Fresnel zone plate (FZP) based optifluidic microscopy (OFM). Compared with conventional optical microscopy, the coherence domain optical imaging has many advantages and greatly extends the application of imaging techniques. OCT, based on low-coherence interferometry, is a high-resolution ...
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    21. Spectral/ Fourier domain Doppler Optical Coherence Tomography in the rodent retina (Thesis)

      Spectral/ Fourier domain Doppler Optical Coherence Tomography in the rodent retina (Thesis)
      Optical Coherence Tomography (OCT) is an emerging imaging technique based on low-coherence interferometry for noninvasive, high- resolution, cross-sectional imaging in a variety of biomedical fields. In ophthalmology, OCT has rapidly become a standard clinical diagnostic tool for retinal diseases, providing visualization of the retina with unprecedented detail. However, conventional time domain OCT systems are limited by low imaging speeds. Conventional time domain OCT systems use a mechanically scanned reference mirror to adjust the reference arm path length in time. Spectral / Fourier domain OCT systems use a spectrometer to detect the interference spectrum and do not require mechanical scanning of the ...
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    22. Plasmon Resonant Nanostructures of Gold for Biomedical Applications (Thesis)

      Plasmon Resonant Nanostructures of Gold for Biomedical Applications (Thesis)
      Advanced optical imaging techniques are emerging as useful ways to screen tissues for the presence of cancer. Plasmon resonant nanoparticles have unique optical properties that make them ideal for use as optical contrast agents. The capacity of these particles to serve a multifunctional role dependent on their composition and the intensity of incident light enables them to serve as diagnostic tools and to provide the therapeutic capability of photo-thermal energy conversion or the controlled release of an encapsulated agent. Likewise, the ability to degrade into components of a clearable size may enable the clinical translation of these types of particles ...
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    23. Novel Biomedical Imaging Systems (Thesis)

      Novel Biomedical Imaging Systems (Thesis)
      The overall purpose of the dissertation is to design and develop novel optical imaging systems that require minimal or no mechanical scanning to reduce the acquisition time for extracting image data from biological tissue samples. Two imaging modalities have been focused upon: a parallel optical coherence tomography (POCT) system and a volume holographic imaging system (VHIS). Optical coherence tomography (OCT) is a coherent imaging technique, which shows great promise in biomedical applications. A POCT system is a novel technology that replaces mechanically transverse scanning in the lateral direction with electronic scanning. This will reduce the time required to acquire image ...
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    24. Image Processing and Clinical Applications of Anterior Segment Optical Coherence Tomography (Thesis)

      Image Processing and Clinical Applications of Anterior Segment Optical Coherence Tomography (Thesis)
      Optical coherence tomography (OCT) is an emerging imaging modality. It provides in vivo cross-sectional images with micron level resolution. OCT is attractive for imaging the anterior eye segment because of its characteristics on high resolution, non-contact, and easy anatomical interpretation. The fast data acquisition rate (>2000 axial scans per second) of current anterior segment OCT systems allows the measurement of corneal dimensions without significant motion error. It also generates huge amount of data. Manual anatomic reconstruction and measurement are time consuming and operator-dependent. Automated image processing and analysis techniques can overcome these limitations and make routine clinical use of OCT ...
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