1. Articles in category: Student Theses

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    1. Development of Swept Source Optical Coherence Tomography and Adaptive Optics Scanning Laser Ophthalmoscopy: Improved Imaging Speed and Handheld Applications (Thesis)

      Development of Swept Source Optical Coherence Tomography and Adaptive Optics Scanning Laser Ophthalmoscopy: Improved Imaging Speed and Handheld Applications (Thesis)

      Optical coherence tomography (OCT) is a noninvasive three-dimensional interferometric imaging technique capable of achieving micrometer scale resolution. It is now a standard of care in ophthalmology, where it is used to improve the accuracy of early diagnosis, to better understand the source of pathophysiology, and to monitor disease progression and response to therapy. In particular, retinal imaging has been the most prevalent clinical application of OCT, but researchers and companies alike are developing OCT systems for cardiology, dermatology, dentistry, and many other medical and industrial applications. Adaptive optics (AO) is a technique used to reduce monochromatic aberrations in optical instruments ...

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      Mentions: Duke University
    2. AUTOMATED MACHINE LEARNING BASED ANALYSIS OF INTRAVASCULAR OPTICAL COHERENCE TOMOGRAPHY IMAGES (Thesis)

      AUTOMATED MACHINE LEARNING BASED ANALYSIS OF INTRAVASCULAR OPTICAL COHERENCE TOMOGRAPHY IMAGES (Thesis)

      Coronary artery disease (CAD) is the leading cause of death in the world. Most acute coronary events (e.g. heart attacks) are due to the rupture of atherosclerotic plaques inside the arteries, however, calcified lesion is the most widely treatable, typically, by stent implantation via percutaneous coronary intervention (PCI). Intravascular Optical Coherence Tomography (IVOCT) imaging has the resolution, contrast, and penetration depth to characterize coronary artery plaques. Conventional manual evaluation of IVOCT images, based on qualitative interpretation of image features, is tedious and time consuming. The aim of this PhD dissertation was to develop advanced algorithms to fully automate the ...

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    3. Attenuation Coefficients, Pixel Intensity, and Texture Analysis as Quantitative Parameters for Analyzing Optical Coherence Tomography Images of Vocal Fold Tissue (Thesis)

      Attenuation Coefficients, Pixel Intensity, and Texture Analysis as Quantitative Parameters for Analyzing Optical Coherence Tomography Images of Vocal Fold Tissue (Thesis)

      Optical coherence tomography is a promising technology to noninvasively assess vocal fold microanatomy. However, many studies using optical coherence tomography to evaluate vocal fold tissue are largely qualitative in nature and lack quantitative measures that might be useful in clinical decision-making. The goal of this thesis was to identify quantitative metrics that can be extracted from optical coherence tomography vocal fold imaging and applied to the surgical subspecialty of Laryngology. The first goal of this study was to determine if optical coherence tomography was sensitive enough to distinguish subtle differences between vocal folds based on vocal fold content using attenuation ...

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    4. Optical coherence tomography Layout Simulation Using MATLAB®

      Optical coherence tomography Layout Simulation Using MATLAB®

      Optical Coherence Tomography (OCT) is a non-invasive optical imaging technique capable of producing 2D images or 3D reconstructions of nonhomogeneous samples. OCT is mainly used in ophthalmology as a powerful tool for the early diagnosis of ocular diseases. With OCT it is possible to obtain high resolution cross-sectional images of ocular structures, such as the retina or the anterior segment. An OCT platform for ocular image acquisition is being developed. It is based on a swept source laser, an InGaAs balanced detector, a data acquisition board installed on a personal computer, and several optical components. The main purpose of this ...

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    5. Acoustic Radiation Force Optical Coherence Elastography : Localized Vs. Wide-Area Perturbation – A Comparison (Thesis)

      Acoustic Radiation Force Optical Coherence Elastography : Localized Vs. Wide-Area Perturbation – A Comparison (Thesis)

      Elastography is a method to image the biomechanical properties of tissues. The experimental setup has a 10 MHz ultrasound transducer (focal length of 5cm and a spot size of 0.3mm localized excitation and unfocused for wide-area excitation) which generates acoustic radiation force (ARF) to perturb the sample and the corresponding mechanical response is imaged with a spectral domain optical coherence tomography (SD-OCT) with a center wavelength of 800 nm and a bandwidth of 180 nm at a transverse optical resolution of 8[mu]m. The existing hypothesis which states that localized harmonic excitation in audio frequency regime has potential ...

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    6. Advanced Monte Carlo Simulation and Machine Learning for Frequency Domain Optical Coherence Tomography

      Advanced Monte Carlo Simulation and Machine Learning for Frequency Domain Optical Coherence Tomography

      Optical Coherence Tomography(OCT) is a popular, rapidly growing imaging technique with an increasing number of bio-medical applications due to its noninvasive nature. However, there are three major challenges in understanding and improving an OCT system: (1) Obtaining an OCT image is not easy. It either takes a real medical experiment or requires days of computer simulation. Without much data, it is difficult to study the physical processes underlying OCT imaging of different objects simply because there aren't many imaged objects. (2) Interpretation of an OCT image is also hard. This challenge is more profound than it appears. For ...

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    7. Development of spectral domain optical coherence tomography for pharmaceutical and medical application

      Development of spectral domain optical coherence tomography for pharmaceutical and medical application

      Spectral-domain optical coherence tomography (SD-OCT) is a type of non-destructive imaging technique that is capable of resolving the inner structure of a sample with micrometre spatial resolution. SD-OCT is based on low coherence interferometry. It utilises a spectrometer to grab the spectral interferogram between the back reflected/scattered light from a reference mirror and a sample. The depth profile, which carries the sample inner structure information, is then generated by a data interpolation and Fourier Transform (FT). Functional coating of solid oral dosage forms optimises the release profile of active pharmaceutical ingredient (API) and results in a desirable API absorption ...

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    8. Characterising the effect of a novel optical delay line and light sources on the resolvability of time domain optical coherence tomography (Thesis)

      Characterising the effect of a novel optical delay line and light sources on the resolvability of time domain optical coherence tomography (Thesis)

      Optical coherence tomography (OCT) is a reflection based imaging technique, with numerous applications, initially in medical diagnostics. Unlike ultrasound, another reflection imaging technique, OCT relies on light scattering in samples, low coherence near- infrared interferometry, and graphical image construction, to acquire 2D and 3D reflectogram images. OCT has resolution an order of magnitude greater than ultrasound, but its depth penetration is less than a few millimetres. Axial resolution is a critical parameter in determining whether OCT can be used to resolve specific features in a sample image. Typically, measures of resolution have been attributed only to the light source’s ...

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    9. Restoration of optical coherence tomography images using stochastic methods (Thesis)

      Restoration of optical coherence tomography images using stochastic methods (Thesis)

      Optical coherence tomography (OCT) is a rapidly growing imaging modality that produces high resolution three dimensional images that can be applied to different medical and industrial applications . Obtaining higher depth of imaging and higher imaging quality are important goals in OCT systems. One of the main factors that affects the penetration depth and imaging quality of OCT systems is the presence of noise. The depth-scan photocurrent of time domain (TD) OCT system is degraded by a class of correlated and signal dependent noise. The joint probability density function of the depth-scan photocurrent can be considered as Gaussian random process that ...

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    10. Heartbeat Optical Coherence Tomography (Thesis)

      Heartbeat Optical Coherence Tomography (Thesis)

      Coronary artery disease (CAD) is a manifestation of atherosclerosis, a systemic inflammatory disease of the arteries that causes the formation of plaques in the artery walls. Different plaques may give rise to different symptoms: a gradual narrowing (stenosis) of the vessel by growth of a fibrous or calcific plaque will cause chest pain (due to cardiac ischemia) upon exertion, a condition called stable CAD. Sudden onset of chest pain, or chest pain at rest, is a symptom of unstable CAD or acute coronary syndrome (ACS), which is associated with thrombus formation on plaques, mostly due to rupture of a lipid-core ...

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    11. Development of a Retinal Eye Tracker for 3D Optical Coherence Tomography (Thesis)

      Development of a Retinal Eye Tracker for 3D Optical Coherence Tomography (Thesis)

      Several eye diseases appear in the posterior part of the eye, i.e. the retina or fundus. Retinal images therefore provide valuable information to identify eye diseases. Optical Coherence Tomography (OCT) is a 3D imaging technique that can image the retina with a resolution and depth penetration that can not be achieved by any other non-invasive imaging technique. Although OCT can achieve high resolution, in vivo measurements are severely limited by eye motion. TNO developed a low-cost eye tracker with improved eye motion tracking compared to current state of the art eye trackers. The eye tracker images the retina at ...

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    12. Ultra-widefield optical coherence tomography of the human retina (Thesis)

      Ultra-widefield optical coherence tomography of the human retina (Thesis)

      Optical coherence tomography (OCT) has become a standard of care in ophthalmology since it was first demonstrated over 20 years ago. Images acquired using commercial OCT systems have been reported to have a maximum imaging length of only 9 mm, which is equivalent to an internal-field of view of 45◦. This narrow-field limitation has been acceptable because of the high level of clinical data available in the macular region and the relative simplicity of imaging this area of the retina. Commercially-available scanning laser ophthalmoloscope (SLO) systems such as the Optos 200Tx are capable of providing a fundus image with an ...

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    13. Evaluation of the Crystalline Lens Gradient Refractive Index using Laser Ray Tracing and Optical Coherence Tomography (Thesis)

      Evaluation of the Crystalline Lens Gradient Refractive Index using Laser Ray Tracing and Optical Coherence Tomography (Thesis)

      The human crystalline lens is a complex and intricate structure that continuously grows throughout our lifetime. The crystalline lens has a non-uniform distribution of protein concentrations which produces an optical gradient within the lens in both the optical and equatorial axes. This gradient refractive index is a unique property of the crystalline lens that significantly contributes to its optical power and aberrations. The objective of this dissertation is to gain a better understanding of the relationship between the crystalline lens shape, its non-uniform gradient refractive index, the lens optical power and aberrations, and their changes with accommodation and age. The ...

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    14. An Evaluation of Silicon Carbide Based Bimorph Actuators for Optical Coherence Tomography Applications

      An Evaluation of Silicon Carbide Based Bimorph Actuators for Optical Coherence Tomography Applications

      Optical coherence tomography (OCT) probes rely on MEMS micro-scanners to provide fast and reproducible scans covering as much area as possible. A popular choice of actuators employed in this role are electrothermal bimorph actuators. They comprise of two layers of different materials which are rigidly joined together. Differential expansion under heating causes the bimorph to deflect. Polycrystalline silicon carbide has been proposed to replace polysilicon as a multi-purpose material in MEMS but it has not been yet explored as a bimorph material. Under this premise, an in-plane bimorph actuator based on doped polycrystalline silicon carbide and silicon was proposed to ...

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    15. 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 polarization-maintaining fiber-based ...

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    16. Ophthalmic Application of Optical Coherence Tomography Based Angiography for Choroidal Imaging (Thesis)

      Ophthalmic Application of Optical Coherence Tomography Based Angiography for Choroidal Imaging (Thesis)

      We demonstrated in vivo choriocapillaris imaging in normal human subjects with a Cirrus HD 5000 spectral domain OCT prototype. With the tracking system installed in the prototype and the montage scanning protocol, wide field OCT angiograms of 9 mm * 11 mm were created. OCT angiography utilizes the intrinsic motion of red blood cells as contrast mechanism therefore requires no exogenous contrast agents as fluorescein angiography and indocyanine green angiography do. Four consecutive OCT scans were acquired at the same location for angiography generating, intensity based, phase based and complex signal based OCTA were all computed and compared. With the ability ...

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    17. Development and Application of Optical Coherence Elastography for Corneal Biomechanics (Thesis)

      Development and Application of Optical Coherence Elastography for Corneal Biomechanics (Thesis)

      The biomechanical properties of the cornea are an important determinant of both the shape and function of the human visual system. Measuring the biomechanical properties on an in vivo basis requires the development of technologies not typically associated with mechanical measurement. Optical Coherence Elastography (OCE) is an optical based measurement capable of measuring micron level displacements in accessible tissues. The application of OCE to corneal measurement was made possible by the use of speckle tracking in the corneal stroma. Application of OCE to human donor corneas was used to measure the biomechanical properties of the human cornea in three separate ...

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    18. Development of Photothermal Optical Coherence Tomography for In Vivo Imaging of Contrast Agents (Thesis)

      Development of Photothermal Optical Coherence Tomography for In Vivo Imaging of Contrast Agents (Thesis)

      Sensitive and specific noninvasive in vivo imaging of contrast agents and endogenous molecules can supply molecular and functional information in animal models, providing essential insight into mechanisms of disease formation and progression, drug delivery, and treatment response. In cancer in particular, high resolution imaging is essential for capturing spatial heterogeneities in molecular expression and the tumor microenvironment that cause significant barriers to treatment efficacy and drug delivery. Optical coherence tomography (OCT) fills the niche of cellular-level resolution and penetration depths in tissue that exceed those obtained with microscopy, an attractive regime for imaging mouse models of cancer. In this dissertation ...

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    19. Design and Fabrication of Optical Polymer Waveguide Devices for Optical Interconnects and Integrated Optical Coherence Tomography (Thesis)

      Design and Fabrication of Optical Polymer Waveguide Devices for Optical Interconnects and Integrated Optical Coherence Tomography (Thesis)

      Optical interconnects is a promising technique to boost the speed of electronic systems through replacing high speed electrical data buses using optical ones. Optical coherence tomography is an attractive imaging technique that has been widely used in medical imaging applications with capability of high resolution subsurface cross sectional imaging in living tissues. Both the optical interconnects and the optical coherence tomography imaging may benefit from the use of integrated optics technology in particular polymer waveguides that can be designed and fabricated to improve the device capability, system compactness, and performance reliability. In this dissertation, we first present our innovative design ...

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    20. Speckle And Motion Based Vascular Image Analysis for Optical Coherence Tomography (Thesis)

      Speckle And Motion Based Vascular Image Analysis for Optical Coherence Tomography (Thesis)

      Optical Coherence Tomography (OCT) is an emerging optical imaging modality that is capable of imaging biological tissues with micron resolution and millimeter penetration depth. In clinical diagnostic imaging and pathology, OCT has helped fill a gap in terms of both resolution and imaging depth, in between traditional fluoroescence based microscopes and non-invasive organ level imaging. In this domain, OCT can be used both as an ex vivo pathological examination tool or in vivo imaging modality.OCT has been successful in ophthalmology owing to its excellent in vivo optical sectioning ability and penetration depth. Over the years, OCT has seen substantial ...

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    21. Postdoctoral Positions in Biomedical Optics and Optical Coherence Tomography at the Center for Ophthalmic Optics & Lasers, Oregon Health & Science University

      Postdoctoral Positions in Biomedical Optics and Optical Coherence Tomography at the Center for Ophthalmic Optics & Lasers, Oregon Health & Science University

      Postdoctoral research opportunities are available in the area of biomedical optics at the Center for Ophthalmic Optics & Lasers ( www.COOLLab.net ) in the Casey Eye Institute, Oregon Health & Science University (OHSU). The COOL laboratory is a multidisciplinary team that incorporates optical scientists, image processing experts, ophthalmologists, statisticians, managers, and technicians. The group collaborates with several institutions to develop novel OCT technology, develop diagnostic and surgical planning software, and conduct clinical trials. The laboratory is well supported by the National Institutes of Health ( http://www.octnews.org/articles/2920025/optical-coherence-tomography-used-500m-of-federall/ ) and industry, and has brought many novel diagnostic technology into clinical ...

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    22. Micro-motion detection by optical coherence tomography (OCT) and its clinical applications (Thesis)

      Micro-motion detection by optical coherence tomography (OCT) and its clinical applications (Thesis)

      Detection of micro-motion on biological tissues has various applications such as ultrasound elastography and magnetic resonance elastography (MRE). Ultrasound transducers, the most commonly used tool to detect endogenous and exogenous micro-motions, have a number of drawbacks: including the requirements of the physical contact with the sample and limited spatial resolution (millimetre scale). The aim of this thesis is to develop a non-contact phase-sensitive imaging technique which is suitable for functional imaging in the micron range which also has the potential for quantitative analysis of relative properties resulting from an appropriate image processing. Concerning imaging techniques, this thesis focused on optical ...

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    23. Investigating Hemodynamics of the Developing Embryonic Heart using Optical Coherence Tomography (Thesis)

      Investigating Hemodynamics of the Developing Embryonic Heart using Optical Coherence Tomography (Thesis)

      Blood flow is a critical factor that regulates developmental programs during cardiogenesis. During early embryonic development, deviations from the normal blood flow pattern have been shown to lead to congenital heart defects including septal defects and outflow tract anomalies. To better understand the role flow and the resulting hemodynamic forces play during cardiovascular development precise tools are needed to rapidly calculate and monitor these forces. Optical coherence tomography (OCT) is a noninvasive imaging modality that is well suited for imaging the developing heart due to its high spatial and temporal resolution. OCT is also capable of analyzing various cardiac functions ...

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    24. Clinical experiences with optical coherence tomography in epithelial (pre)malignancies (Thesis)

      Clinical experiences with optical coherence tomography in epithelial (pre)malignancies (Thesis)

      More than 80% of all cancers originate from the epithelium. Epithelium lines organs and cavities inside the body and forms the skin on the outside. Epithelium regenerates constantly and the tissue is prone to the development of cancer. In this thesis we concentrate on cancers arising in the epithelial lining of the male and female genital area and of the skin. The thesis describes the potential of optical coherence tomography (OCT) to differentiate between normal tissue and (pre)malignant tissue in epithelial cancers. The work can be divided in research performed in the genital area and the field of melanoma.

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