1. Articles in category: Student Theses

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    1. Cascade Optical Coherence Tomography (C-OCT) for Surface Form Metrology of - ProQuest

      Cascade Optical Coherence Tomography (C-OCT) for Surface Form Metrology of - ProQuest

      Freeform optical components enable dramatic advances in optical system performance and packaging. As the saying goes, “one cannot make what one cannot measure.” Surface form metrology of as-built freeform optics remains a challenge and an active area of research. In this dissertation, a novel cascade optical coherence tomography (C-OCT) technique was conceived towards addressing this metrology challenge. The C-OCT theoretical framework was developed, and a metrology system was built to demonstrate its working principle and metrology capability experimentally. Three significant areas were investigated to realize a C-OCT metrology system with nanometer-level measurement uncertainty. First, the sample arm requirements concerning telecentricity ...

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    2. Reflectance-Based Structural Quantification of the Healthy and Glaucomatous Retinal Nerve ...

      Reflectance-Based Structural Quantification of the Healthy and Glaucomatous Retinal Nerve ...

      Glaucoma is a group of progressive optic neuropathies that can lead to irreversible vision loss if left untreated. Spectral-domain optical coherence tomography (SD-OCT) is an important imaging tool used in the diagnosis and management of glaucoma. It provides thickness measurements of the retinal nerve fiber layer (RNFL), a useful index for monitoring progressive thinning that occurs from damage. However, there exists high between-subject variability in RNFL thickness in people free of eye disease. Another approach is RNFL reflectance, proposed in 1921 when reduction in reflectance was observed in damaged RNFL. Despite numerous reports from the past century supporting this, clinically ...

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    3. Applications of Visible-Light Optical Coherence Tomography in the Eye and Brain -

      Applications of Visible-Light Optical Coherence Tomography in the Eye and Brain -

      Optical coherence tomography (OCT) is a non-invasive, label-free technology that can image biological tissues in vivo with micrometer-scale resolution. Since its development in 1991, OCT has been successfully commercialized and widely adopted in the clinic for the diagnosis and monitoring of retinal diseases. A typical commercial OCT system may have an axial resolution of 5-10 micrometers. By shortening the wavelength range of the light source, visible-light OCT (vis-OCT) enables an improved axial resolution of 1-micrometer, improved tissue scattering contrasts, and additional functional information. The bulk of this dissertation focuses on vis-OCT imaging of the Schlemm’s canal and limbal vascular ...

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    4. The Advanced Applications for Optical Coherence Tomography in Skin Imaging (Thesis)

      The Advanced Applications for Optical Coherence Tomography in Skin Imaging (Thesis)

      Optical coherence tomography (OCT), based on low coherent interferometry, is an FDAapproved non-invasive imaging modality. It uses a low coherent near-infrared laser around the wavelength of 1300 nm [1]. OCT has been widely used in ophthalmology to assess retina thickness and anatomical changes. In 1997, this technology was tested to image the cross-section of human skin in vivo, and it was able to visualize different skin layers and skin appendages [2]. Although, OCT has great potential in monitoring skin morphologic changes, skin cancer diagnosis, and tumor margin assessment [3], it is not well recognized and adopted by many dermatologists. Therefore ...

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    5. The Advanced Applications for Optical Coherence Tomography in Skin Imaging (Thesis)

      The Advanced Applications for Optical Coherence Tomography in Skin Imaging (Thesis)

      I NTRODUCTION Optical coherence tomography (OCT), based on low coherent interferometry, is an FDA - approved non - invasive imaging modality. It uses a low coherent near - infrared laser around the wavelength of 1300 nm [1] . OCT has been widely used in ophthalmology to assess r etina thickness and anatomical changes. In 1997, this technology was tested to image the cross - section of human skin in vivo , and it was able to visuali ze different skin layer s and skin appendages [2] . Although , OCT has great potential in monitoring skin morphologic changes, skin cancer diagnosis , and tumor margin assessment [3] , i t ...

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    6. Advances in Optical Coherence Tomography for Retinal Oximetry and Angiography (Thesis)

      Advances in Optical Coherence Tomography for Retinal Oximetry and Angiography (Thesis)

      Optical coherence tomography (OCT) is a high-resolution, non-contact, three-dimensional imaging technique, which has revolutionized the diagnosis and treatment of retinal diseases. Visible-light OCT (vis-OCT) extends OCT by enabling retinal oximetry – the measurement of oxygen saturation of hemoglobin from within individual retinal blood vessels. Three advances in the vis-OCT technique are presented: an improved vis-OCT oximetry method based on circumpapillary scan and graph-search segmentation; the calibration, simulation, and correction of spectroscopic sensitivity rolloff for vis-OCT oximetry; and the measurement of the inner retinal oxygen metabolism in the 50/10 oxygen-induced retinopathy model, an animal model for human retinopathy of prematurity. Optical ...

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    7. Comparing different methods to measure biofilm thickness: the techniques are: optical coherence tomography, confocal laser scanning microscopy and low load compression test (Thesis)

      Comparing different methods to measure biofilm thickness: the techniques are: optical coherence tomography, confocal laser scanning microscopy and low load compression test (Thesis)

      Biofilm formation remains a serious concern in industry and in the medical field. They are responsible for huge economical losses in many industrial sectors and for serious infections associated with biomaterial implants and medical devices. These infections are hard to treat because bacteria within the biofilm are more resistant to antibiotics and to the host immune system. Therefore, studying biofilm properties and mechanisms is of utmost relevance to develop efficient approaches to deal with this drawback. Biofilm thickness is an important parameter in biofilm characterization. The main purpose of this thesis was to assess the suitability of Optical Coherence Tomography ...

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    8. 400 kHz Spectral Domain Optical Coherence Tomography for Corneal Imaging

      400 kHz Spectral Domain Optical Coherence Tomography for Corneal Imaging

      The cornea is the transparent, outermost layer of the human eye that contributes approximately 70% of the refractive power of the eye in air. It is composed of five major tissue layers: the epithelium, the Bowman’s membrane, the stroma, the Descemet’s membrane, and the endothelium. Corneal diseases such as Keratoconus and Fuchs’ dystrophy can change the morphology of some or all of the corneal layers, which can lead to vision impairment and eventually blindness. For example, Keratoconus causes localizes thinning and thickening of the corneal epithelium, damage to the collagen structure of the corneal stroma (scarring) and alteration ...

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    9. COMPUTATIONAL IMAGING AS APPLIED TO CORONARY ARTERY OPTICAL COHERENCE TOMOGRAPHY

      COMPUTATIONAL IMAGING AS APPLIED TO CORONARY ARTERY OPTICAL COHERENCE TOMOGRAPHY

      Patients with inadequate stent expansion are at high risk for adverse outcomes, including stent thrombosis as well as in-stent restenosis. Both are well-described complication usually causing acute coronary syndromes and, in the worst-case scenario, sudden cardiac death. Once a stent is deployed in atherosclerotic tissue that is highly resistant to dilation, it is often tricky to fully expand the implanted stent, even using a noncompliant balloon. Careful evaluation of these risks prior to the intervention will aid treatment planning, including potential application of a plaque modification strategy. Moderate to severe calcification in the treated vessel restrict full deployment of a ...

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    10. 4 year funded PhD studentship in Dental OCT at University College London

      4 year funded PhD studentship in Dental OCT at University College London

      Transforming Dental Imaging using Optical Coherence Tomography Primary Supervisor: Dr Peter Munro Clinical Supervisor : Prof Francesco D'Aiuto A 4 year PhD studentship funded by the Royal Society and Department of Medical Physics and Biomedical Engineering is available jointly in the UCL Department of Medical Physics and Biomedical Engineering and the UCL Eastman Dental Institute . Funding will be at least the UCL minimum (£17,609). Ideally, the successful applicant would start as soon as possible. The intended start date is 1st May 2022. The successful candidate will join the UCL CDT in Intelligent, Integrated Imaging in Healthcare (i4health) cohort and ...

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    11. OPTICAL COHERENCE ELASTOGRAPHIC AND TOMOGRAPHIC MICROSCOPY FOR RESOLUTION-ENHANCED MICROMECHANICAL AND STRUCTURAL IMAGING OF BIOLOGICAL SYSTEMS

      OPTICAL COHERENCE ELASTOGRAPHIC AND TOMOGRAPHIC MICROSCOPY FOR RESOLUTION-ENHANCED MICROMECHANICAL AND STRUCTURAL IMAGING OF BIOLOGICAL SYSTEMS

      Optical microscopy has had a revolutionary impact in the biomedical sciences. Among other modalities, optical coherence tomography (OCT) offers a unique capability for label-free structural imaging of biological systems at cellular resolution over millimeter-scale volumetric field-of-view. The rapidly growing field of mechanobiology has presented immense opportunities for not only structural microscopy, but also functional imaging of biomechanical properties with emerging optical elastography techniques. Importantly, attention has been given to the role of biomechanical interactions between cells and the extracellular matrix (ECM) in various biological processes, including onset and progression of cancer, stem cell differentiation, morphogenesis, and wound healing. Although a ...

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    12. The Use of Optical Coherence Tomography to Asscess Water Transport Through The Urothelium of The Porcine Bladder

      The Use of Optical Coherence Tomography to Asscess Water Transport Through The Urothelium of The Porcine Bladder

      Recent reports pointed out that the urothelium was a permeable membrane and had some sensory and signaling functions. The aquaporins expression has been found in the urothelium, implicit water transport through the urothelium. However, this process has never been observed directly. This study aims to better understand water transport through urothelium and how sodium chloride affects urothelial integrity during the water transport process. We hypothesize that optical coherence tomography could be used to monitor the dynamical water transport process through the porcine bladder urothelium. The water transport process could be affected by the sodium chloride concentration over the urothelium. And ...

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    13. Optical coherence tomography in multiple sclerosis: contributions to understanding its use in clinical practice

      Optical coherence tomography in multiple sclerosis: contributions to understanding its use in clinical practice

      Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS) affecting more than two million people worldwide. The disease is characterised by inflammation in the CNS (leading to episodes of focal neurological dysfunction, i.e. relapses) and neurodegeneration (leading to progressive and permanent disability). Depending on the localisation of the CNS damage, patients exhibit a wide range of symptoms including muscle weakness, sensory disturbances, problems with coordination, fatigue and cognitive impairment. Visual symptoms are common as well, with more dan 50% of MS patients experiencing one or more episodes of optic neuritis (ON) during the course of ...

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    14. Evaluating Severity of Microbial Keratitis Using Optical Coherence Tomography

      Evaluating Severity of Microbial Keratitis Using Optical Coherence Tomography

      Microbial keratitis (MK) is an infection of the cornea caused a variety of pathogens that can lead to significant visual loss. The current diagnosis relies on clinical examination and microbiological testing. New in-vivo imaging techniques are now available that can assist the diagnosis and follow the clinical course of this disease. Using optical coherence tomography (OCT) it is possible to obtain high resolution imaging for the cornea. The purpose of this thesis is to demonstrate a link between the latest OCT technology and clinical outcomes by using a severity index scoring tool. A prospective study was undertaken including 68 eyes ...

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    15. Photonic integrated circuits for optical coherence tomography (Thesis)

      Photonic integrated circuits for optical coherence tomography (Thesis)

      Optical coherence tomography (OCT) is a well established 3D cross-sectional imaging method for retinal diagnostics. However, the method is largely limited to a clinical setting, with more widespread utilization being hindered by both the size and the cost of current systems. A reduction of both would significantly increase the potential application range, especially, for point of care diagnostics. One approach to reduce the size and cost is the utilization of photonic integrated circuits (PICs) to substitute bulk and/or fiber optic components used in conventional OCT systems. PICs provide optical systems in a chip-scale format, similar to integrated circuits (ICs ...

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    16. Invasive Coronary Artery Imaging Using Optical Coherence Tomography: A Cost-effectiveness and Implementation Process Analysisg (Thesis)

      Invasive Coronary Artery Imaging Using Optical Coherence Tomography: A Cost-effectiveness and Implementation Process Analysisg (Thesis)

      The aim of this project was the implementation of optical coherence tomography (OCT), an invasive intracoronary imaging (ICI) tool used for the visualization of coronary arteries. The implementation was performed in a structured manner by: (1) A literature review into the current applications of OCT in relation to current standards; (2) A thesis feasibility study into clinical practices, professional views and other processes regarding ICI; (3) A Master’s thesis including a cost-effectiveness analysis (CEA) and the actual implementation of OCT at the department. The project started with a literature review about the current applications of OCT in relation to ...

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    17. DEVELOPMENT OF PHASE DECORRELATION OPTICAL COHERENCE TOMOGRAPHY FOR ASSESSMENT OF THE OCULAR LENS AND CORNEA

      DEVELOPMENT OF PHASE DECORRELATION OPTICAL COHERENCE TOMOGRAPHY FOR ASSESSMENT OF THE OCULAR LENS AND CORNEA

      The human ocular system is tightly maintained in order to sharply focus images onto the retina. Our understanding of the ocular system has benefited from the study of biomechanical phenomena. For instance, the field has begun to understand a range of diseases as biomechanical in origin – such as keratoconus, glaucoma, and myopia. This mechanical understanding of disease has led to the development of new treatments, primarily crosslinking, which directly address the mechanical deficiency and have generally proved to be highly effective. Keratoconus, which until recently could only be treated through contact lenses and corneal transplants, can now be treated relatively ...

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    18. Multidimensional Data Processing for Optical Coherence Tomography Imaging (Thesis)

      Multidimensional Data Processing for Optical Coherence Tomography Imaging (Thesis)

      Optical Coherence Tomography (OCT) is a medical imaging technique which distinguishes itself by acquiring microscopic resolution images in-vivo at millimeter scale fields of view. The resulting in images are not only high-resolution, but often multi-dimensional to capture 3-D biological structures or temporal processes. The nature of multi-dimensional data presents a unique set of challenges to the OCT user that include acquiring, storing, and handling very large datasets, visualizing and understanding the data, and processing and analyzing the data. In this dissertation, three of these challenges are explored in depth: sub-resolution temporal analysis, 3-D modeling of fiber structures, and compressed sensing ...

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    19. Computational Methods for Image Acquisition and Analysis with Applications in Optical Coherence Tomography

      Computational Methods for Image Acquisition and Analysis with Applications in Optical Coherence Tomography

      The computational approach to image acquisition and analysis plays an important role in medical imaging and optical coherence tomography (OCT). This thesis is dedicated to the development and evaluation of algorithmic solutions for better image acquisition and analysis with a focus on OCT retinal imaging. For image acquisition, we first developed, implemented, and systematically evaluated a compressive sensing approach for image/signal acquisition for single-pixel camera architectures and an OCT system. Our evaluation outcome provides a detailed insight into implementing compressive data acquisition of those imaging systems. We further proposed a convolutional neural network model, LSHR-Net, as the first deep-learning ...

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    20. Towards estimation of optical and structural ophthalmic properties based on optical coherence tomography

      Towards estimation of optical and structural ophthalmic properties based on optical coherence tomography

      Early diagnosis of retinal diseases such as glaucoma will benefit from unbiased an precise estimation of both optical and structural properties of the RNFL as they provide a better understanding of the tissue characteristics. The main objective of this thesis was first to improve the estimation of the attenuation coefficients of layered samples and, second, to estimate the structural properties of RNFL. Unbiased estimation of optical tissue properties such as the attenuation coefficient require a model of the recorded OCT signal. To study the characteristics of the OCT signal, in Chapter 2, two simulation methods were presented for homogeneous samples ...

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    21. Optical coherence tomography (OCT) and irreversible electroporation (IRE) in the diagnosis and treatment of renal masses

      Optical coherence tomography (OCT) and irreversible electroporation (IRE) in the diagnosis and treatment of renal masses

      The first aim of this thesis is to investigate the diagnostic value of needle-based, percutaneous optical coherence tomography (OCT) in the differentiation of renal masses. Secondly, the feasibility and safety of percutaneous, irreversible electroporation (IRE) are assessed for the treatment of SRMs.

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    22. Multidimensional Data Processing for Optical Coherence Tomography Imaging (Thesis)

      Multidimensional Data Processing for Optical Coherence Tomography Imaging (Thesis)

      Optical Coherence Tomography (OCT) is a medical imaging technique which distinguishes itself by acquiring microscopic resolution images in-vivo at millimeter scale fields of view. The resulting in images are not only high-resolution, but often multi-dimensional to capture 3-D biological structures or temporal processes. The nature of multi-dimensional data presents a unique set of challenges to the OCT user that include acquiring, storing, and handling very large datasets, visualizing and understanding the data, and processing and analyzing the data. In this dissertation, three of these challenges are explored in depth: sub-resolution temporal analysis, 3-D modeling of fiber structures, and compressed sensing ...

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    23. The use of optical coherence tomography to enhance surgical margin assessment for canine mast cell tumors (Thesis)

      The use of optical coherence tomography to enhance surgical margin assessment for canine mast cell tumors (Thesis)

      Experiment 1: Objective: To document the appearance of artifacts created by commonly encountered surgical conditions and instrumentation on optical coherence tomography (OCT) and compare these findings with histopathology. Study design: Ex vivo study Animals: 5 canine cadavers Methods: Skin, subcutaneous fat, skeletal muscle, and fascia samples were obtained from fresh canine cadavers. Blood pooling, hemostatic crushing, scalpel blade cut, monopolar electrosurgery, bipolar vessel sealing device and ultrasonic energy surgical artifacts were induced on each tissue type. Each specimen was interrogated with OCT and subsequently histologically processed. Results: The majority of surgical instrumentation used for tumor excision created a high-scattering region ...

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    24. Automated Algorithm for Optical Coherence Tomography (OCT) Images of 3D Spheroids (Thesis)

      Automated Algorithm for Optical Coherence Tomography (OCT) Images of 3D Spheroids (Thesis)

      The application of three-dimensional (3D) tumor spheroids has been expanding due to their ability to closely mimic several features of solid tumors such as their cellular heterogeneity/organization and growth kinetics. Optical Coherence Tomography (OCT) system has been utilized to characterize 3D morphological and physiological information of multicellular tumor spheroids. In order to characterize and analyze the results of 3D OCT spheroid datasets, there is a need to develop an automated algorithm with high accuracy that can calculate the volume of a tumor spheroid and its necrotic tissues. The developed automated algorithm can automatically detect the margin of the 3D ...

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