1. Articles in category: Student Theses

    1-24 of 247 1 2 3 4 ... 9 10 11 »
    1. Analysis of Retinal Vascular Density using Optical Coherence Tomography Angiography, to Differentiate Healthy, Glaucoma Suspect and Glaucomatous Eyes (Thesis)

      Analysis of Retinal Vascular Density using Optical Coherence Tomography Angiography, to Differentiate Healthy, Glaucoma Suspect and Glaucomatous Eyes (Thesis)

      OBJECTIVES: To study and compare vascular density in papillary retina using OCT Angiography in normals, Glaucoma suspects (Ocular hypertension), early POAG patients and its correlation with RNFL thickness and field changes. METHODS: All volunteers fulfilling eligibility criteria and willing to participate in the study, were recruited in three arms (Minimum sample size of 16 each) and underwent a full ophthalmic examination and investigations (Central corneal thickness, automated visual field testing (HFA 24-2 SITA, threshold test), optical coherence tomography (OCT) RNFL thickness (3.4 mm diameter circle around disc) and OCT angiography (3x3 mm scan) of optic disc, papillary and peri-papillary ...

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    2. Clinical feasibility of optical coherence elastography for tumour margin assessment in breast-conserving surgery (Thesis)

      Clinical feasibility of optical coherence elastography for tumour margin assessment in breast-conserving surgery  (Thesis)

      Currently, 20-30% of patients undergoing breast-conserving surgery require a second surgery due to tumour being found within the margin of the excised lump, determined days following surgery. The work presented in this thesis aims to develop a wide­field optical coherence elastography system suitable for intraoperative margin assessment to reduce additional procedures. Early feasibility studies are presented investigating the ability for three optical coherence elastography variants to visualise a range of tumour morphologies In human breast tissue. The thesis demonstrates the clinical feasibility of optical coherence elastography for tumour margin assessment and provides a strong foundation for future clinical translation.

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    3. Estimation of volumetric optical coherence tomography measurements from 2D color fundus photographs using machine learning

      Estimation of volumetric optical coherence tomography measurements from 2D color fundus photographs using machine learning

      The optic nerve head is the location in the rear of the eye where the nerves exit the eye towards the brain. Swelling of the optic nerve head (ONH) is most accurately quantitatively assessed via volumetric measures using 3D spectral-domain optical coherence tomography (SD-OCT). However, SD-OCT is not always available as its use is primarily limited to specialized eye clinics rather than in primary care or telemedical settings. Thus, there is still a need for severity assessment using more widely available 2D fundus photographs. In this work, we propose machine-learning methods to locally estimate the volumetric measurements (akin to those ...

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    4. Optical coherence tomography in people with epilepsy: symmetry and clinical correlations (Thesis)

      Optical coherence tomography in people with epilepsy: symmetry and clinical correlations (Thesis)

      Optical Coherence Tomography (OCT) provides detailed images by assessing the scattering properties of a tissue (1)⁠. OCT is precise and easily repeatable. It is quick to obtain and does not cause any significant discomfort to patients. For these reasons, it is a useful clinical tool to diagnose and monitor many conditions. Peripapillary retinal nerve fibre layer (pRNFL) thickness measured by OCT was recently confirmed as a biomarker of white matter (WM) integrity in various neurological conditions (2)⁠. In epilepsy, retinal thinning is found in people exposed to vigabatrin (3)⁠ but also in people not exposed to this antiepileptic drug (AED ...

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    5. Application of functional optical coherence tomography angiography in neurovascular research (Thesis)

      Application of functional optical coherence tomography angiography in neurovascular research (Thesis)

      Optical coherence tomography (OCT) is a revolutionary non-invasive imaging technique that can perform high-resolution, cross-sectional tomographic imaging of the internal microstructure in biological tissues by measuring backscattered or backreflected light. Its functional extension, OCT angiography (OCTA), analyzes the intrinsic scattering property of the heterogenous tissue bed to extract dynamic blood flow signals to the capillary level without a need of contrast agents. Aside from the commonly known application of OCTA in clinical ophthalmology for imaging the retinal blood flow in human subjects, the technique has recently emerged as a useful tool in pre-clinical neuroscience for imaging cerebral microcirculation and dynamics ...

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    6. Precision Microfabrication of Optical Probes for Intravascular Diagnostics (Thesis)

      Precision Microfabrication of Optical Probes for Intravascular Diagnostics (Thesis)

      This thesis details a collection of design, optimisation, fabrication and characterisation work to form fiber-optic probes and optical phantom devices for intravascular diagnostics in minimally invasive surgery (MIS). Optically generated ultrasound is an emerging technique to create broadband high frequency ultrasound via the photoacoustic effect. In the first segment of this thesis, the development of a novel miniature fiber-optic ultrasound transmitter is detailed. A morphologically controlled coating was formed at the endface of a multimode optical fiber by controlled electrospinning of a carbon-nanotube composite. Efficient optical ultrasound generation was realised, with signal amplitude, bandwidth and device form factor suited to ...

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    7. Techniques in Optical Coherence and Resonance for Sensing (Thesis)

      Techniques in Optical Coherence and Resonance for Sensing (Thesis)

      Optical sensors are ubiquitous for their precision and non-contact acquisition, and have enjoyed widespread use in applications such as biosensing, environmental monitoring, and security. Despite their sensitivity, many of these sensors rely on costly laboratory instrumentation, and are not adaptable to the ever-growing volume of consumer detectors and optics that are readily available, making their application limited to benchtop analytics. This work leverages plasmonic resonances and optical coherence phenomena to make modifications upon traditional sensing formats that improve their sensitivity when deployed in off-the-shelf optical systems. In particular, we demonstrate that label-free plasmonic sensors can be combined with electrochemical impedance ...

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    8. Improving optical coherence tomography theories and techniques for advanced performance and reduced cost (Thesis)

      Improving optical coherence tomography theories and techniques for advanced performance and reduced cost (Thesis)

      Optical coherence tomography (OCT) has been developed as a high-resolution three-dimensional imaging technique for clinical diagnosis. This thesis proposes several theoretical discoveries and technical improvements to the current OCT systems aiming to drastically reduce system costs while achieving the state-of-the-art performance. Polarization-sensitive OCT (PS-OCT) is a functional extension of conventional OCT which offers the depth-resolved birefringence imaging capability. To resolve local retardation in tissue samples, the current PS-OCT system employs two multiplexed polarization states to illuminate the sample under investigation and detects the backscattered light with two detection channels. We observed that the polarization state of light after round-trip propagation ...

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    9. Optical Coherence Photoacoustic Microscopy (OC-PAM) for Multimodal Imaging (Thesis)

      Optical Coherence Photoacoustic Microscopy (OC-PAM) for Multimodal Imaging (Thesis)

      Optical coherence tomography (OCT) and Photoacoustic microscopy (PAM) are two noninvasive, high-resolution, three-dimensional, biomedical imaging modalities based on different contrast mechanisms. OCT detects the light backscattered from a biological sample either in the time or spectral domain using an interferometer to form an image. PAM is sensitive to optical absorption by detecting the light-induced acoustic waves to form an image. Due to their complementary contrast mechanisms, OCT and PAM are suitable for being combined to achieve multimodal imaging. In this dissertation, an optical coherence photoacoustic microscopy (OC-PAM) system was developed for in vivo multimodal retinal imaging with a pulsed broadband ...

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    10. Parapapillary Atrophy : prevalence and distribution of alpha, beta and gamma parapapillary atrophy identified by the means of spectral domain optical coherence tomography (SD-OCT) (Thesis)

      Parapapillary Atrophy : prevalence and distribution of alpha, beta and gamma parapapillary atrophy identified by the means of spectral domain optical coherence tomography (SD-OCT) (Thesis)

      Purpose: The purpose of this study was to estimate the prevalence and distribution of alpha, beta and gamma parapapillary atrophy in diabetic adults over the age of 40 years, as identified by the means of spectral domain optical coherence tomography (SD-OCT). Methods: All subjects underwent anamnesis, subjective binocular refraction and imaging with SD-OCT in both eyes. The obtained OCT sections provided 24 degree sections for assessment of the parapapillary retina, which were analysed for the presence of alpha, beta and gamma parapapillary atrophy. Results: 135 eyes of 70 subjects, with mean age of 61.33 years (range: 43-81, SD: 9 ...

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    11. DEEP LEARNING OPTIMIZATION FOR OPTICAL COHERENCE TOMOGRAPHY MEDICAL IMAGE ANALYSIS (Thesis)

      DEEP LEARNING OPTIMIZATION FOR OPTICAL COHERENCE TOMOGRAPHY MEDICAL IMAGE ANALYSIS (Thesis)

      Optical Coherence Tomography (OCT) is an interferometric imaging modality that can visualize biological microstructure via cross-sectional images. OCT can construct 3D image data and produce a concise summary of the scanned objects. Because of the non-invasiveness and swift diagnostic procedure, OCT becomes a high potential technology for the real-time surgery guidance. Machine learning algorithms have been widely applied and investigated for automatic medical image analysis. This research proposes two deep learning models for OCT human tissue image classification. Based on the inception module structure, a deep dilated depthwise separable convolution neural network (DDSCN) model is proposed to combine the strength ...

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    12. Quantitative Phase Imaging of Biological Samples using Optical Coherence Tomography (Thesis)

      Quantitative Phase Imaging of Biological Samples using Optical Coherence Tomography (Thesis)

      Advancement in the diagnostic techniques is required for early detection of the disease which will avoid the many risks to patients. This thesis research work describes a novel imaging technique for quantitative phase imaging of the biological samples. We developed a full-field optical spatial coherence microscopy (FF-OSCM) system based on monochromatic laser. The system is characterized in terms of axial resolution, lateral resolution, phase sensitivity and phase stability. The developed system exploits the property of spatial coherence and its performance is comparable to the conventional optical coherence microscopy based on temporal coherence. The system is used for the quantification of ...

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    13. The multi-spectral signal properties of multiple reference optical coherence tomography (Thesis)

      The multi-spectral signal properties of multiple reference optical coherence tomography (Thesis)

      Efforts to reduce the size and costs of optical coherence tomography systems (OCT) for consumer applications, in general, focus on Fourier-domain OCT, due to its potential to be integrated on an optical chip, implementing the interferometer and the spectrometer together as a compact system. An alternative and near-term solution is multiple reference OCT. This technique utilizes a partial mirror in the reference arm to enhance the axial imaging depth of traditional time-domain OCT. The motivation of this thesis is to investigate the performance and sensitivity characteristics of multiple reference OCT in comparison to time-domain OCT. Due to the partial mirror ...

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    14. Dual modality optical coherence tomography : Technology development and biomedical applications (Thesis)

      Dual modality optical coherence tomography : Technology development and biomedical applications (Thesis)

      Optical coherence tomography (OCT) is a cross-sectional imaging modality that is widely used in clinical ophthalmology and interventional cardiology. It is highly promising for in situ characterization of tumor tissues. OCT has high spatial resolution and high imaging speed to assist clinical decision making in real-time. OCT can be used in both structural imaging and mechanical characterization. Malignant tumor tissue alters morphology. Additionally, structural OCT imaging has limited tissue differentiation capability because of the complex and noisy nature of the OCT signal. Moreover, the contrast of structural OCT signal derived from tissue’s light scattering properties has little chemical specificity ...

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    15. Computational Methods to Quantify Human Lens Shape and Optical Properties Using Laser Ray Tracing and Optical Coherence Tomography (Thesis)

      Computational Methods to Quantify Human Lens Shape and Optical Properties Using Laser Ray Tracing and Optical Coherence Tomography (Thesis)

      Vision is worsening on a global scale. Myopia, a visual condition where distant objects appear blurry, is increasing in prevalence at an alarming rate. This condition typically starts during childhood and progressively worsens, potentially leading to more severe visual conditions if left unchecked. Currently, the best treatment method to slow myopic progression is heavily debated as the etiology of myopia is not fully understood. The development of effective long-term solutions require a better understanding of how vision changes with age. The cornea and lens, the length of the human eye, and the surrounding ocular media dictate visual quality. Extensive studies ...

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    16. A Novel Use of Optical Coherence Tomography for the Assessment of Ocular Torsion (Thesis)

      A Novel Use of Optical Coherence Tomography for the Assessment of Ocular Torsion (Thesis)

      Abnormal ocular torsion is most frequently the result paresis of the fourth cranial nerve. The presence of torsion can be a barrier to fusion, in which case, surgical intervention is required for a patient to have single vision. Clinically, ocular torsion can be measured either subjectively or objectively, the latter traditionally using the relationship between the fovea and the optic disc. However, previous literature has shown inconsistencies between torsion a patient’s perceived subjective torsion, and the amount of anatomical fundus torsion. Therefore, the aim of the current study was to investigate the relationship of subjective and objective ocular torsion ...

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    17. SPECTRAL CALIBRATION FOR SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY BASED ON B-SCAN DOPPLER SHIFT WITH IN SITU. TISSUE IMAGES (Thesis)

      SPECTRAL CALIBRATION FOR SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY BASED ON B-SCAN DOPPLER SHIFT WITH IN SITU. TISSUE IMAGES (Thesis)

      We propose a simple method of linearizing spectral interference fringes of spectral domain optical coherence tomography (SDOCT) based on B-scan Doppler frequency shift (DFS), which can be obtained by offsetting the laser beam from the pivot of a scanning mirror. We show that DFS is proportional to wavenumber. A DFS curve can be then extracted from either a single mirror image or multiple tissue images. By examining the convergence of the nonlinear coefficients of the DFS curve fitted with a polynomial equation, in situ. tissue images themselves can be used to linearize the wavenumber without requiring mirror images or additional ...

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    18. Application of optical coherence tomography for improved in-situ flaw detection in nylon 12 selective laser sintering (Thesis)

      Application of optical coherence tomography for improved in-situ flaw detection in nylon 12 selective laser sintering (Thesis)

      Despite significant advances made since the inception of selective laser sintering (SLS), many of the same problems identified by early researchers including high part porosity, inadequate surface finish, and part strength uncertainty persist today. Because of these challenges, quality validation and improved process control continue to be identified as critical areas of improvement in industry roadmaps. To address these issues, an optical coherence tomography (OCT) sensor is investigated for feasibility of use in in-situ flaw detection in SLS. Benchtop OCT imaging of nylon in solid, liquid, and resolidified phases revealed subsurface imaging through liquid and resolidified nylon material was possible ...

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    19. Co-alignment of detectors in dual-channel spectrometers by optical coherence tomography (Thesis)

      Co-alignment of detectors in dual-channel spectrometers by optical coherence tomography (Thesis)

      This work presents a method for detectors co-alignment in dual-channel spectrometer using optical coherence tomography. The method is proposed for the ELOIS (Enhanced Light Offner Imaging Spectrometer) developed by the AMOS company (Advance Mechanical and Optical Systems). This company designs and builds optical components and instruments related to the space industry and one of their current project is the ELOIS instrument. A crucial aspect in the development of the instrument is the correct alignment of the focal plane assembly components. During this phase, the two detectors of the spectrometer need to be correctly co-aligned with each other in the six ...

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    20. Quantification of Ciliary Muscle Function through Morphological Analysis of Optical Coherence Tomography Images (Thesis)

      Quantification of Ciliary Muscle Function through Morphological Analysis of Optical Coherence Tomography Images (Thesis)

      s we grow older, we lose our ability to accommodate, or focus from far to near, in a condition called presbyopia. Presbyopia is an issue in our everyday life, complicating routine tasks such as using smartphones or reading street signs while driving. To develop effective therapies to treat presbyopia, we need to understand the changes in the eye that occur with age. We need to be able to observe the eye in vivo as accommodation occurs. The present dissertation focuses on the part of the eye responsible for starting the mechanics of accommodation, the ciliary muscle. Imaging of the muscle ...

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    21. Application of Multi-Tonal Complex with Optical Coherence Tomography Imaging System for Vibrometric Analysis of Inner-Ear Structures (Thesis)

      Application of Multi-Tonal Complex with Optical Coherence Tomography Imaging System for Vibrometric Analysis of Inner-Ear Structures (Thesis)

      Currently, research is being conducted on single tone sound transduction within the auditory portion of the inner ear, the cochlea [1]. The study of cochlear mechanics in large rodents has provided important insight into cochlear function [1]. Additionally, multi-tone stimuli can provide a new perspective in vibrometric analyses that could be used in audiometry as a measure of hearing loss for patients in terms of both magnitude and their unique frequency envelope. Therefore, the proposed study was aimed to test the recent implementation of multitone calibration into an existing python program, PyVib2, which was used during Optical Coherence Tomography (OCT ...

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    22. Fiber-optic probe and bulk-optics Spectral Domain Optical Coherence tomography systems for in vivo cochlear mechanics measurements (Thesis)

      Fiber-optic probe and bulk-optics Spectral Domain Optical Coherence tomography systems for in vivo cochlear mechanics measurements (Thesis)

      Acquiring the motions of the inner ear sensory tissues provides insight to how the cochlea works. For this purpose, Spectral Domain Optical Coherence Tomography (SDOCT) is an ideal tool as it has a penetration depth of several millimeters. SDOCT can not only image inside the cochlear partition, but also measure the sample structures’ simultaneous displacements. We customized a commercial Spectral Domain Optical Coherence Tomography system for such functions and detailed the software and hardware steps so this powerful system could be more accessible to auditory researchers. The cochlea is surrounded by bones and tissues, and damage to it would make ...

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    23. Title Automated Plaque Characterization of Intravascular Optical Coherence Tomography (IVOCT) Images Using 3D Cryo-image/Histology Validation (Thesis)

      Title Automated Plaque Characterization of Intravascular Optical Coherence Tomography (IVOCT) Images Using 3D Cryo-image/Histology Validation (Thesis)

      Intravascular optical coherence tomography (IVOCT) is a high-resolution (10-20 µm), high-contrast, catheter-based imaging technology that can identify major coronary plaques types (fibrous, lipid, and calcium). However, with >500 images generated in a single 2.5 second scan, automation is needed to facilitate live-time clinical use and off-line assessment of drug therapeutics. Therefore, we developed machine learning approaches for automated plaque characterization using cryo-imaging/histology for validation. However, we confronted a challenge in that IVOCT images are obtained perpendicular to the imaging catheter, while cryo-image volumes display the true 3D vessel geometry at a higher sampling rate. Our solution was to ...

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    24. Development of High-Speed Optical Coherence Tomography for Time-Lapse Nondestructive Characterization of Samples (Thesis)

      Development of High-Speed Optical Coherence Tomography for Time-Lapse Nondestructive Characterization of Samples (Thesis)

      Yongyang Huang received his B.S. degree in Physics at Peking University in July 2013. Since September 2013, he has been a Ph.D student in the Department of Electrical & Computer Engineering (ECE) in Lehigh University. His research area is focused on optical coherence tomography (OCT) and its applications in biomedical imaging.

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    1-24 of 247 1 2 3 4 ... 9 10 11 »
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