Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

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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2007 - 200912010 - 20172

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    3D Multimodal Image Registration: Application to equine PET and CT images
    (2017) Regani, Sai Deepika; Chellappa, Rama; Beylin, David; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Positron Emission Tomography (PET) is being widely used in veterinary medicine in recent years. Although it was limited to small animals because of its classical design and the large amount of radionuclide doses required, PET imaging in horses became possible with the introduction of a portable PET scanner developed by Brain Biosciences Inc. It was observed that this new modality could capture abnormalities like lesions that Computed Tomography (CT), Magnetic Resonance Imaging (MRI) and other modalities could not. Since 2016, PET imaging in horses is being studied and analysed. While PET provides functional information characterizing the activity of lesions, it is useful to combine information from other modalities like CT and match the structural information to develop an accurate spatial representation of the data. Since biochemical changes occur much earlier than structural changes, this helps detect lesions and tumours during the early stages. Multimodal image registration is used to achieve this goal. A series of steps are proposed to automate the process of registration of equine PET and CT images. Multimodal image registration using landmark-based and intensity-based techniques are studied. It is observed that a few tissues are not imaged in the PET, which makes image segmentation, an important preprocessing step in the registration process. A study of the segmentation algorithms relevant to the field of medical imaging is presented. The performance of segmentation algorithms improved with the extent of manual interaction and intensity-based registration gave the smallest time complexity with reasonable accuracy.
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    Dose and image quality considerations in computed tomography
    (2011) Abboud, Samir; Kyprianou, Iacovos; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The increased use of Computed Tomography as an imaging modality is of concern because of the growing body of evidence linking radiation exposure to cancer incidence. However, a framework does not yet exist for balancing the immediate needs of the clinical task (image quality) with future risks due to the imaging procedure (dose). We developed a method to estimate the shape and thickness of materials yielding attenuation equivalent to that of bow-tie-shaped filters in clinical scanners. The results are especially useful for accurate modeling in Monte Carlo simulations of radiation transport. We then investigated measures of dose and image quality using both simulation and laboratory experimentation. We found that current measures of dose are robust under current clinical conditions. We also found that measures of image quality are object and task specific.
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    Radiation dose reduction strategies for intraoperative guidance and navigation using CT
    (2007-02-20) Shetye, Avanti Satish; Shekhar, Raj; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The advent of 64-slice computed tomography (CT) with high speed scanning makes CT a highly attractive and powerful tool for navigating image guided procedures. Interactive navigation needs scanning to be performed over extended time periods or even continuously. However, continuous CT is likely to expose the patient and the physician to potentially unsafe radiation levels. Before CT can be used appropriately for navigational purposes, the dose problem must be solved. Simple dose reduction is not adequate, because it degrades image quality. This study proposes two strategies for dose reduction; the first is the use of a statistical approach representing the stochastic nature of noisy projection data at low doses to lessen image degradation and the second, the modeling of local image deformations in a continuous scan. Taking advantage of modern CT scanners and specialized hardware, it may be possible to perform continuous CT scanning at acceptable radiation doses for intraoperative navigation.