Theses and Dissertations from UMD

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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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Subject: search.filters.subject.Optical Coherence Tomography

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    Direct Laser Writing-Enabled Microstructures with Tailored Reflectivity for Optical Coherence Tomography Phantoms
    (2023) Fitzgerald, Declan Morgan; Sochol, Ryan D; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    As the continuous push to improve medical imaging techniques produces increasingly complex systems, so too must the phantoms critical to the accurate evaluation of these systems evolve. The inclusion of precise geometries is a well documented gap in optical coherence tomography (OCT) phantoms, a gap felt more severely as the technology improves. This thesis seeks to investigate the feasibility of utilizing new manufacturing techniques in the production of OCT phantoms with complex geometries while developing a phantom to determine the sensitivity of OCT systems. The new manufacturing methods include the replication of microstructures printed via direct laser writing into PMMA photoresist, the tailored smoothing of surface roughness inherent to direct laser writing, and the selective retention of surface roughness in certain regions. Each of these methods were implemented in the manufacture of an OCT sensitivity phantom and were found to be effective in each of their respective goals.The efficacy of the sensitivity phantom in evaluating the minimum reflectance still detectable by an OCT system shows promise. Effective reflectivity ranging from 0 to ~1 was accomplished within a single angled element and should provide a basis for determining the minimum reflectivity that results in a signal-to-noise ratio of 1. Further improvements must be made to the phantom footprint and manufacturing before the phantom’s reliability is certain.
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    Optics And Computer Vision For Biomedical Applications
    (2018) Wang, Bohan; Chen, Yu; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Bioengineering is at the cross sections of biology, clinical technology, electrical engineering, computer science and many other domains. The smooth translation of domain technologies to clinics is not just about accuracy and practicality of the technology. It also has to take into account the accessibility (cost and portability), the patients’ comfort and the ease to adapt into the workflow of medical professionals. The dissertation will explore three projects, (1) portable and low-cost near infrared florescence imaging system on mobile phone platform, (2) computer aided diagnosis software for diagnosing chronical kidney disease based on optical coherence tomography (OCT) images and (3) the tracking and localization of hand-held medical imaging probe. These projects aim to translate and adapt modern computation hardware, data analysis models and computer vision technologies to solve and refine clinical diagnosis applications. The dissertation will discuss how the translation, tradeoffs and refinement of those technologies can bring a positive impact on the accuracy, ease of conduct, accessibility and patients’ comfort to the clinical applications.
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    NORMAL AND BARRETT’S ESOPHAGUS PHANTOM FOR OPTICAL COHERENCE TOMOGRAPHY (OCT) SYSTEMS EVALUATED USING TEXTURE ANALYSIS METHODS
    (2016) Bandukwala, Abbas Quresh; Ehrman, Sheryl; Chen, Yu; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Optical coherence tomography (OCT) is increasingly used to image tissue microstructure for diagnostic purposes. OCT imaging is currently being researched to diagnose, survey, and monitor Barrett’s esophagus. However due to the many differences between OCT systems, a method to calibrate or provide a standard is needed. This research developed esophagus phantoms that represent normal and Barrett’s esophagus tissue. When imaged by OCT systems the phantoms mimicked the visual aspects of the normal esophagus tissue and Barrett’s esophagus tissue. The images produced with the phantom were then evaluated with three different texture analysis methods to quantify the phantoms. Finally, the images from the phantoms were compared to clinical images for visual alignment and texture accuracy. The results demonstrated that these esophagus phantoms can be distinguished both visually and through quantifying the images in the texture.
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    OPTICAL COHERENCE TOMOGRAPHY FOR NEUROSURGEY AND CANCER RESEARCH
    (2014) Liang, Chia-Pin; Chen, Yu; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Optical Coherence Tomography (OCT) provides non-labeling, real-time and high resolution images, which has the potential to transform the paradigm of surgical guidance and preclinical animal studies. The design and development of OCT devices for neurosurgery guidance and novel imaging algorithms for monitoring anti-cancer therapy have been pursued in this work. A forward-imaging needle-type OCT probe was developed which can fit into minimally invasive tools (I.D. ~ 1mm), detect the at-risk blood vessels, and identify tissue micro-landmarks. This promising guidance tool improves the safety and the accuracy of needle-based procedures, which are currently performed without imaging feedback. Despite the great imaging capability, OCT is limited by the shallow imaging depth (1-2 mm). In order to address this issue, the first MRI compatible OCT system has been developed. The multi-scale and multi-contrast MRI/OCT imaging combination significantly improves the accuracy of intra-operative MRI by two orders (from 1mm to 0.01 mm). In contrast to imaging systems, a thin (0.125 mm), low-cost (1/10 cost of OCT system) and simple fiber sensor technology called coherence gated Doppler (CGD) was developed which can be integrated with many surgical tools and aid in the avoidance of intracranial hemorrhage. Furthermore, intra-vital OCT is a powerful tool to study the mechanism of anti-cancer therapy. Photo-immunotherapy (PIT) is a low-side-effect cancer therapy based on an armed antibody conjugate that induces highly selective cancer cell necrosis after exposure to near infrared light both in vitro and in vivo. With novel algorithms that remove the bulk motion and track the vessel lumen automatically, OCT reveals dramatic hemodynamic changes during PIT and helps to elucidate the mechanisms behind the PIT treatment. The transformative guidance tools and the novel image processing algorithms pave a new avenue to better clinical outcomes and preclinical animal studies.