Physics Commons^™

Magnetic Resonance Systems Development For Point-Of-Care Mri Platforms, Eric J. Lessard

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging utilizes electromagnets to produce anatomical images in both clinical and research settings. In the race towards increasing performance head-optimized scanners have begun playing a significant role in providing high quality imaging of the head. However, they are implemented using smaller geometries and as such fail to allow entrance of the patient past their shoulders. This is overcome by designing asymmetric gradient coils which have their imaging region located towards one end of the gradient coil, as opposed to the geometric center, allowing brain imaging. There exists interest in compact configurations which allow imaging further into the cervical …

Hyperpolarized Carbon-13 Magnetic Resonance Measurements Of Tissue Perfusion And Metabolism, Keith Michel

Dissertations & Theses (Open Access)

Hyperpolarized Magnetic Resonance Imaging (HP MRI) is an emerging modality that enables non-invasive interrogation of cells and tissues with unprecedented biochemical detail. This technology provides rapid imaging measurements of the activity of a small quantity of molecules with a strongly polarized nuclear magnetic moment. This polarization is created in a polarizer separate from the imaging magnet, and decays continuously towards a non-detectable thermal equilibrium once the imaging agent is removed from the polarizer and administered by intravenous injection. Specialized imaging strategies are therefore needed to extract as much information as possible from the HP signal during its limited lifetime.

In …

Design Of Radio-Frequency Arrays For Ultra-High Field Mri, Ian R O Connell

Electronic Thesis and Dissertation Repository

Magnetic Resonance Imaging (MRI) is an indispensable, non-invasive diagnostic tool for the assessment of disease and function. As an investigational device, MRI has found routine use in both basic science research and medicine for both human and non-human subjects.

Due to the potential increase in spatial resolution, signal-to-noise ratio (SNR), and the ability to exploit novel tissue contrasts, the main magnetic field strength of human MRI scanners has steadily increased since inception. Beginning in the early 1980’s, 0.15 T human MRI scanners have steadily risen in main magnetic field strength with ultra-high field (UHF) 8 T MRI systems deemed to …

Hyperpolarized 3he Magnetic Resonance Imaging Phenotypes Of Chronic Obstructive Pulmonary Disease, Damien Pike

Electronic Thesis and Dissertation Repository

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death in the world. Identifying clinically relevant COPD phenotypes has the potential to reduce the global burden of COPD by helping to alleviate symptoms, slow disease progression and prevent exacerbation by stratifying patient cohorts and forming targeted treatment plans. In this regard, quantitative pulmonary imaging with hyperpolarized 3He magnetic resonance imaging (MRI) and thoracic computed tomography (CT) have emerged as ways to identify and measure biomarkers of lung structure and function. 3He MRI may be used as a tool to probe both functional and structural properties of the lung …

A Non-Contrast Magnetic Resonance Imaging Technique To Assess Blood-Brain Barrier Permeability, Harini Pandithasekera

Electronic Thesis and Dissertation Repository

The Blood-brain barrier (BBB) regulates the entry of compounds between the blood and the brain, thus plays an important role in brain homeostasis. Studies indicate in disease states such as Alzheimer’s the BBB integrity is compromised. The motive of this project is to investigate the sensitivity of the diffusion-weighted arterial spin labeling (DW-ASL) technique to detect water exchange. Testing the sensitivity requires a reliable method of opening the barrier at specific locations of the brain. Here, a unique technology named focused ultrasound (FUS) has been used to mimic a compromised BBB environment.

A series of experiments were conducted in a …

Optimization Of A Boundary Element Approach To Electromagnet Design With Application To A Host Of Current Problems In Magnetic Resonance Imaging, Chad T. Harris

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging (MRI) has proven to be a valuable methodological approach in both basic research and clinical practice. However, significant hardware advances are still needed in order to further improve and extend the applications of the technique. The present dissertation predominantly addresses gradient and shim coil design (sub-systems of the MR system).

A design study to investigate gradient performance over a set of surface geometries ranging in curvature from planar to a full cylinder using the boundary element (BE) method is presented. The results of this study serve as a guide for future planar and pseudo-planar gradient systems for …