1. Articles in category: Student Theses

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    1. Supercontinuum in the practice of Optical Coherence Tomography with emphasis on noise effects (Thesis)

      Supercontinuum in the practice of Optical Coherence Tomography with emphasis on noise effects (Thesis)

      Optical Coherence Tomography (OCT) is an imaging modality which has proven, since the early 1990s, its incredible potential. Nowadays, numerous fields of medical investigation, such as Ophthalmology, Dermatology or Cardiovascular imaging, would not be the same without the diagnostic tools bring by OCT. This tremendous development has been supported by industry support through improvement of dedicated components such as lasers, cameras and optics. A great example of this development is the evolution of Supercontinuum (SC) sources. Due to the extremely broad spectrum cover by SC sources, their high power density and high spatial coherence, it seems obvious to use them ...

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    2. From sample structure to optical properties and back : A theoretical framework for quantitative OCT and its clinical application (Thesis)

      From sample structure to optical properties and back : A theoretical framework for quantitative OCT and its clinical application (Thesis)

      The aim of this thesis is to provide a methodology to extract quantitative parameters from optical coherence tomography (OCT) images and to relate these parameters to sample properties such as structure, organization and flow. OCT uses near-infrared light to acquire 3D images of biological tissue, with a resolution around 5-15 μm and an imaging depth of approximately 2 mm. OCT can be a useful clinical tool for minimally-invasive, high-resolution imaging of tissue structures and morphology. In addition to morphological imaging, quantification of scattering properties from OCT images is a potential complementary source of information on microscopic tissue properties, which can ...

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    3. Investigating the reliability and clinical utility of minimally invasive portable electroretinography and optical coherence tomography techniques in children undergoing vigabatrin therapy (Thesis)

      Investigating the reliability and clinical utility of minimally invasive portable electroretinography and optical coherence tomography techniques in children undergoing vigabatrin therapy (Thesis)

      The antiepileptic drug for Infantile Spasms – vigabatrin, has been associated with retinal toxicity in over one third of children treated. Young and non-verbal children cannot cooperate with conventional adult-oriented monitoring devices, therefore a safe and reliable technique to monitor for vigabatrin retinal toxicity is missing. This study evaluated the tolerability, reliability and clinical feasibility of two alternative, handheld systems for assessment of retinal function: the RETeval ERG and Envisu OCT. We found that non-sedated children showed poor tolerability on the RETeval ERG. Under sedation the same children showed high tolerability on the handheld OCT. Responses from both techniques demonstrated good ...

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    4. A flow cytometric and optical coherence analysis of the role of microparticles as determinants of plaque instability in acute coronary syndrome (FOAM study) (Thesis)

      A flow cytometric and optical coherence analysis of the role of microparticles as determinants of plaque instability in acute coronary syndrome (FOAM study) (Thesis)

      Introduction: Microparticles (MPs) are implicated in the pathogenesis of coronary artery disease (CAD). / Aims: To determine whether circulating MPs correlate with high-risk coronary atherosclerotic plaque phenotype. / Methods: 25 patients with CAD undergoing percutaneous coronary intervention (PCI) were recruited; 13 were diagnosed to have acute coronary syndrome (ACS) & 12 with stable angina (SA). We characterized and compared coronary atherosclerotic plaque burden and vulnerable plaque phenotype by three-vessel optical coherence tomography (OCT) between ACS and SA groups. Endothelial (EMPs), platelet (PMPs), Neutrophil (NMPs), tissue factor (TFMPs) and smooth muscle (SMMPs) were quantified by flow cytometry, compared between groups pre PCI, post PCI ...

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    5. Fast simulation of finite-beam optical coherence tomography of inhomogeneous turbid media (Thesis)

      Fast simulation of finite-beam optical coherence tomography of inhomogeneous turbid media (Thesis)

      We developed a fast simulator of finite-beam optical coherence tomography (OCT) of inhomogeneous turbid media. Our Sequential Monte Carlo (MC) based finite beam OCT simulator can reach more than a hundred times faster than one that represents a finite OCT’s incident beam as a superposition of infinitely thin beams, i.e., a superposition-based MC simulator. In this thesis, first, we highlight the lesser-known correspondence between the commonly used MC simulation of light in turbid media, and Sequential MC based solution of the Radiative Transfer Equation (RTE). Second, we describe the implementation of our simulator of finite-beam OCT as a ...

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    6. Clinical Applications of Angiographic Optical Coherence Tomography (Thesis)

      Clinical Applications of Angiographic Optical Coherence Tomography (Thesis)

      Angiographic optical coherence tomography (OCTA) has rapidly found utility within many facets of medical research. Here OCTA algorithms are enabled on a commercial OCT system and verified through correlation with intra-vital light microscopy (IVM). While the vast majority of vessels were accurately measured, smaller vessels (<30µm) have a tendency to appear dilated in comparison to IVM. The technique was also expanded upon to facilitate the imaging of subcutaneous murine fibrosarcoma tumours, negating the requirement for an intra-vital window. It was found that vessel measurement sensitivity was sufficiently high such that the morphologies of vessels within tumours expressing unique vascular ...

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    7. Fusion of X-ray angiography and optical coherence tomography for coronary flow simulation

      Fusion of X-ray angiography and optical coherence tomography for coronary flow simulation

      In conclusion, this thesis proposes a new approach for reconstruction of coronary artery and the implanted BRS by fusion of OCT and X-ray angiography to analyze intracoronary ESS in vivo. The studies conducted in this thesis demonstrate the feasibility of the proposed approach to analyze the detailed local coronary hemodynamics in patients, including the SS patterns after BRS implantation in coronary bifurcations. We observed that in vivo assessment of ESS was closely related to: (1) reconstruction of the side branches; (2) reconstruction of the BRS; (3) patient-specific flow; (4) post-processing portion size in which ESS was calculated. Based on these ...

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    8. Assessment and Diagnosis of Human Ovarian and Colorectal Cancer using Optical and Photoacoustic Imaging (Thesis)

      Assessment and Diagnosis of Human Ovarian and Colorectal Cancer using Optical and Photoacoustic Imaging (Thesis)

      Optical imaging modalities have the advantage of high resolution, label free, rapid, low cost imaging for both in vivo and ex vivo diagnosis of biological tissues. Optical scattering, which is the main contrast of optical coherence tomography (OCT), is related to elastic scattering components, mainly stromal collagen. Tissue elasticity has recently emerged as an important diagnostic parameter associated with tumor development and progression and is also related to the distribution of structural components such as tissue collagen. We have used an optical coherence tomography elastography (OCTE) system for characterizing the differences in the micro-mechanical properties of benign and malignant human ...

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    9. OPTICAL COHERENCE TOMOGRAPHY FOR CORONARY ARTERY DISEASE (Thesis)

      OPTICAL COHERENCE TOMOGRAPHY FOR CORONARY ARTERY DISEASE (Thesis)

      The aim of this thesis was to develop a software pipeline for tissue analysis in IVOCT by systematically addressing different open questions for analysis. In Chapter 2, we report on a first attempt to quantify the correlation between the position of the catheter with respect to the luminal wall and the image intensities. We implemented the Depth-Resolved (DR) model for IVOCT images in Chapter 3. In addition to the attenuation coefficient, we further extended the model to estimate a backscatter term, and proposed an algorithm to exclude the noisy region. For the first time, it was implemented in IVOCT images ...

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    10. Characterisation of textured surfaces under a laminar flow by Optical Coherence Tomography (Thesis)

      Characterisation of textured surfaces under a laminar flow by Optical Coherence Tomography (Thesis)

      Textured surfaces are present everywhere in nature and in our daily life, interacting constantly with a flow. In this report, we focus on how a textured surface with pillars responds to a laminar flow inside a confined channel. The study is mainly focused on the measurements of the bending of the pillars and of the velocity field, using optical coherence tomography. The potential of this technique, which is not very common in microfluidics, is explored here to characterise our system and its limits are discussed. The measurements of the bending and of the velocity field allow to get the value ...

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    11. Automated Segmentation of Retinal Optical Coherence Tomography Images (Thesis)

      Automated Segmentation of Retinal Optical Coherence Tomography Images (Thesis)

      Aim Optical Coherence Tomography (OCT) is a fast and non-invasive medical imaging technique which helps in the investigation of each individual retinal layer structure. For early detection of retinal diseases and the study of their progression, segmentation of the OCT images into the distinct layers of the retina plays a crucial role. However, segmentation done by the clinicians manually is extremely tedious, time-consuming and variable with respect to the expertise level. Hence, there is an utmost necessity to develop an automated segmentation algorithm for retinal OCT images which is fast, accurate, and eases clinical decision making. Methods Graph-theoretical methods have ...

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    12. Developing algorithms for the analysis of retinal Optical Coherence Tomography images (Thesis)

      Developing algorithms for the analysis of retinal Optical Coherence Tomography images (Thesis)

      Vision loss, with a prevalence loss greater than 42 million in the United States is one of the major challenges of today's health-care industry and medical science. Early detection of different retinal-related diseases will dramatically reduce the risk of vision loss. Optical Coherence Tomography (OCT) is a relatively new imaging technique which is of great importance in the identification of ocular and especially retinal diseases. Thus, the efficient analysis of OCT images provides several advantages. In this thesis, we propose a series of image processing and machine learning techniques for the automated analysis of OCT images. The proposed methodology ...

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    13. Automated Glaucoma Detection using Retinal Layers Segmentation and Optic Cup to Disc Ratio in OCT Images (Thesis)

      Automated Glaucoma Detection using Retinal Layers Segmentation and Optic Cup to Disc Ratio in OCT Images (Thesis)

      Glaucoma is an eye problem that affects the retina and weakens the nerve cells that assist in visual recognition. This disease can be the cause of blindness and visual impairments if not treated in time. Increase in Intraocular pressure (IOP) is the main cause for glaucoma presence and succession. The diameter of the optic cup within optic disc region is increased due to the excessive retinal pressure. Cup to disc ratio (CDR) is the mainly used clinical feature to diagnose glaucoma. The increment in CDR is the main factor to classify glaucoma patients. This causes the retina to be affected ...

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    14. ALGORITHMS FOR OPTICAL COHERENCE TOMOGRAPHY AND ITS CLINICAL APPLICATIONS (Thesis)

      ALGORITHMS FOR OPTICAL COHERENCE TOMOGRAPHY AND ITS CLINICAL APPLICATIONS (Thesis)

      Optical Coherence Tomography (OCT) is a clinically adapted, high resolution, non-invasive, non-contact imaging modality that gives a cross-sectional depth-resolved image of the biological sample. Several modifications in OCT instrumentation and development of new reconstruction algorithms have made OCT a potential diagnostic tool. This thesis discusses a free space experimental set-up and development of effective image reconstruction algorithm for Spectral Domain Optical Coherence Tomography (SD-OCT). This algorithm is initially validated on the in-house developed phantoms and later applied on the various biological samples. The same algorithm is implemented for oral tissue and stomach tissue analysis. Further, the OCT imaging was explored ...

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    15. Differences in optical coherence tomography assessment of radial peripapillary capillaries with axial length and optic nerve head morphology (Thesis)

      Differences in optical coherence tomography assessment of radial peripapillary capillaries with axial length and optic nerve head morphology (Thesis)

      INTRODUCTION: Optic nerve head morphological parameters and axial length have been shown to be associated with altered retinal perfusion and microvascular characteristics. The radial peripapillary capillaries (RPC) are a fine network of vessels embedded within the retinal nerve fiber layer which can be visualized using optical coherence tomography (OCT) angiography. RPC is susceptible to ocular hypertension, ischemia, trauma, or biomechanical stress. Since axially myopic eyes have greater propensity for developing glaucoma, assessing the relationship between morphological parameters and RPC characteristics may contribute to evidence important to understanding the pathophysiology of glaucoma and other optic neuropathies. PURPOSE: To investigate the association ...

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    16. Quantitative Optical Coherence Tomography Methods for Functional Microvascular Imaging (Thesis)

      Quantitative Optical Coherence Tomography Methods for Functional Microvascular Imaging (Thesis)

      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 ...

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    17. High Resolution Wide Field-of-View Optical Coherence Tomography For 3D Imaging (Thesis)

      High Resolution Wide Field-of-View Optical Coherence Tomography For 3D Imaging (Thesis)

      Optical coherence tomography (OCT) is a noninvasive, cross-sectional, and three-dimensional (3D) tomographic imaging modality. It offers subsurface deeper penetration depth and larger scan area than confocal microscopy as well as higher resolution than ultrasound imaging, very suitable for 3D in vivo imaging of eyes, skins, blood vessels, and other non-biomedical samples. However, there is a trade-off problem among lateral resolution, lateral field of view (FOV), and axial imaging depth, limiting the performance of OCT systems. In this dissertation, we report our studies to solve these problems and to make the OCT a competitive tool for a variety of 3D imaging ...

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    18. Non-destructive biomechanical testing of tissues using a vibrational optical coherence tomography setup (Thesis)

      Non-destructive biomechanical testing of tissues using a vibrational optical coherence tomography setup (Thesis)

      The mechanical properties of tissues and implants contribute to their physiological functionality, and have been vast areas of research in fields such as Dermatology, Cardiology, Neurology, Ophthalmology, Orthopedics and Urology. Several tests and modalities have been used to measure the mechanical properties of tissues and implants including tensile, compressive, shear, and bending in one or more axial directions. However, majority of these tests are destructive, rendering the material unusable post-testing; whereas most of the non-destructive imaging modalities such as magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR) and ultrasound are costly and have lower spatial resolution. Optical coherence tomography (OCT ...

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    19. Safeguarding ovarian tissue autotransplantation in cancer patients (Thesis)

      Safeguarding ovarian tissue autotransplantation in cancer patients (Thesis)

      Autotransplantation of ovarian tissue can be used to restore fertility in cancer patients following gonadotoxic treatment. Whether this procedure is safe remains unclear, as current tumor detection methods (e.g. PCR analysis, immunohistochemistry) render the ovarian tissue unsuitable for transplantation. As a result, the current tumor detection approach includes assessment of only one or two cortical ovarian fragments that are not transplanted, whereas cortical ovarian tissue fragments that are placed back remain unchecked. The studies described in this thesis focused on determining the risk of reintroducing malignant tumor cells following ovarian tissue autotransplantation using the current tumor detection approach, and ...

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    20. Structural and functional optical coherence tomography imaging of the colon (Thesis)

      Structural and functional optical coherence tomography imaging of the colon  (Thesis)

      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 ...

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    21. Polarization-maintaining fiber-based Optical Coherence Tomography and its applications (Thesis)

      Polarization-maintaining fiber-based Optical Coherence Tomography and its applications (Thesis)

      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 ...

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    22. REVISITING THE VASCULAR THEORY OF GLAUCOMA USING OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY (Thesis)

      REVISITING THE VASCULAR THEORY OF GLAUCOMA USING OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY (Thesis)

      Glaucoma is a chronic progressive opƟ c neuropathy resulƟ ng from the apoptosis of reƟ nal ganglion cells (RGC).1 It is characterized by typical opƟ c disc and reƟ nal nerve fi ber layer (RNFL) changes with or without visual fi eld (VF) changes. The standard tests used to assess the amount of structural (opƟ c disc and RNFL) changes in current day clinical pracƟ ce are opƟ c disc photography (Figure 1, upper panel) and opƟ cal coherence tomography (OCT, Figure 1, middle panel). OCT also images the inner reƟ nal layers at the macular region (nerve fi ...

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    23. Reflectometry and Optical Coherence Tomography for Noninvasive High Resolution Tear Film ...

      Reflectometry and Optical Coherence Tomography for Noninvasive High Resolution Tear Film ...

      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 ...

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    24. Automatic optical coherence tomography imaging analysis for retinal disease screening (Thesis)

      Automatic optical coherence tomography imaging analysis for retinal disease screening (Thesis)

      The retina and the choroid are two important structures of the eye and on which the quality of eye sight depends. They have many tissue layers which are very important for monitoring the health and the progression of the eye disease from an early stage. These layers can be visualised using Optical Coherence Tomography (OCT) imaging. The abnormalities in these layers are indications of several eye diseases that can lead to blindness, such as Diabetic Macular Edema (DME), Age-related Macular Degeneration (AMD) and Glaucoma. If the retina and the choroid are damaged there is little chance to recover normal sight ...

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