Other Physics Commons^™

Feasibility Of Functional Mri On Point-Of-Care Mr Platforms, Arjama Halder

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging (MRI) has proven to be a clinically valuable tool that can produce anatomical and functional images with improved soft tissue contrast compared to other imaging modalities. There has recently been a surge in low- and mid-field scanners due to hardware developments and innovative acquisition techniques. These compact scanners are accessible, offer reduced siting requirements and can be made operational at a reduced cost.

This thesis aims to implement blood-oxygen-level-dependent (BOLD) resting-state functional MRI (fMRI) at such a mid-field point-of-care scanner. The availability of this technique can be beneficial to get neurological information in cases of traumatic brain …

Towards Clinical Microscopic Fractional Anisotropy Imaging, Nico Jj Arezza

Electronic Thesis and Dissertation Repository

Microscopic fractional anisotropy (µFA) is a diffusion-weighted magnetic resonance imaging (dMRI) metric that is sensitive to neuron microstructural features without being confounded by the orientation dispersion of axons and dendrites. µFA may potentially act as a surrogate biomarker for neurodegeneration, demyelination, and other pathological changes to neuron microstructure with greater specificity than other dMRI techniques that are sensitive to orientation dispersion, such as diffusion tensor imaging. As with many advanced imaging techniques, µFA is primarily used in research studies and has not seen use in clinical settings.

The primary goal of this Thesis was to assess the clinical viability of …

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 …

A Molecular Dynamics Study Of Polymer Chains In Shear Flows And Nanocomposites, Venkat Bala

Electronic Thesis and Dissertation Repository

In this work we study single chain polymers in shear flows and nanocomposite polymer melts extensively through the use of large scale molecular dynamics simulations through LAMMPS. In the single polymer chain shear flow study, we use the Lattice Boltzmann method to simulate fluid dynamics and also include thermal noise as per the \emph{fluctuation-dissipation} theorem in the system. When simulating the nanocomposite polymer melts, we simply use a Langevin thermostat to mimic a heat bath. In the single polymer in shear flow study we investigated the margination of a single chain towards solid surfaces and how strongly the shear flow …

Methodologies For Metal Functionalization Of Phosphorus Based Photopolymer Networks, Vanessa Béland

Electronic Thesis and Dissertation Repository

Photopolymer networks with phosphonium cation, alkyl phosphine and olefin functionality were designed, synthesized and functionalized with metals by metathesis, coordination and hydrometallation reactions, respectively. The materials were strategically designed so that the metal functionalization step could be monitored and quantified. In some cases, this involved characterization by IR, NMR, or X-ray spectroscopic techniques, or by comparison to molecular analogues. It was found that by using a bi-functional photopolymer network, the material could be bi-metallized by orthogonal mechanisms. All metallized polymer networks were tested for their suitability as precursors to metal-containing ceramics. The polymers were pyrolyzed, and on analysis it was …

Sympathetic Physics: The Keely Motor And The Laws Of Thermodynamics In Nineteenth-Century Culture, Robert Macdougall

History Publications

In Philadelphia in the 1870s, John Worrell Keely announced the invention of a fantastic new motor that could, he promised, drive locomotives, power factories, and even defy gravity without fuel or heat. The Keely Motor became the most notorious perpetual motion scheme of the nineteenth century, attracting believers and investors for nearly thirty years. This article explores the “work” the motor performed for Keely, his supporters, and his critics—not physical work, but financial, cultural, and psychological. To investors, the Keely Motor represented a dream of riches without effort. To Keely’s critics, the motor offered an opportunity to defend the legitimacy …

Performance Impact Of Different Lower-Limb Setup Positions In The Backstroke Swimming Start, Gordon E. Barkwell

Electronic Thesis and Dissertation Repository

The performance impact of different knee extension angles in the setup position for a backstroke start was evaluated using an instrumented starting surface. Ten backstroke swimmers completed maximum-effort starts in each of two setup positions: one with the knees flexed, and one with the knees extended. The start handles and touchpad were instrumented with tri-axial force plates. Activity of major hip and knee extensors was measured using surface electromyography. Body position was recorded throughout the start using two high-speed cameras. There was no difference in time to 10 m between the two conditions, indicating there is likely no advantage in …

Effects Of High Pressure On Photochemical Reactivity Of Organic Molecular Materials Probed By Vibrational Spectroscopy, Jiwen Guan

Electronic Thesis and Dissertation Repository

Chemical transformations of molecular materials induced by high pressure and light radiation exhibit novel and intriguing aspects that have attracted much attention in recent years. Particularly, under the two stimuli, entire transformations of molecular species can be realized in condensed phases without employing additional chemical constraints, e.g., the need of solvents, catalysts or radical initiators. This new synthetic approach in chemistry therefore satisfies increasing need for production methods with reduced environmental impacts. Motivated by these promises, my Ph. D thesis focuses on this state-of-the-art branch of high-pressure photochemistry. Specifically, high pressure is employed to create the necessary reaction conditions to …

Optimization Of Design Procedures For Delta Relaxation Enhanced Magnetic Resonance, Daniel J. Martire

Electronic Thesis and Dissertation Repository

Delta relaxation enhanced magnetic resonance (dreMR) is a magnetic resonance imaging (MRI) method that produces contrast based on longitudinal relaxation dispersion. Through modulation of the magnetic field using an actively-shielded, field-cycling insert coil, this technique increases probe specificity and suppresses remaining signal. However, significant improvements are needed. This thesis addresses two advancements in dreMR with a focus on optimizing design procedures. A general procedure was developed to design split power solenoid magnets. The procedure was then applied to the design of a switched-field exposure system. A coil was constructed and the method was validated. This procedure can be used for …

Methods For Improved Estimation Of Low Blood Velocities Using Vector Doppler Ultrasound, Bushra Hussain

Electronic Thesis and Dissertation Repository

Accurate estimation of low 3D blood velocities, such as near the wall in recirculation or disturbed flow regions, is important for accurate mapping of velocities to improve estimations of wall shear stress and turbulence, which are associated risk factors for vascular disease and stroke. Doppler ultrasound non-invasively measures blood-velocities but suffers from two major limitations addressed in this thesis. These are angle dependence of the measurements, which requires the knowledge of beam-to-flow angle, and the wall-filter. The high-pass wall filter that is applied to attenuate the high-intensity low-frequency signal from tissue and slowly moving vessel wall also attenuates any low …

Static Magnetic Field Interactions Of Medical Devices In The Mri Environment, Spencer Baird Parent

Electronic Thesis and Dissertation Repository

Background: The current procedures and guidelines for testing medical devices require that conservative testing be carried-out using the “worst-case” device or device configuration for each interaction (force, torque, heating, et cetera) of importance, and the results of those tests be used to inform regulatory labeling for that device. One of the most difficult elements of carrying out the above procedure is the determination of what represents a “worst-case” device or device configuration. A simulation “pipeline” would enable a systematic procedure for identification of the worst-case device or device configuration for magnetic force from an otherwise impossibly large set of options. …

Optimizing Respiratory Gated Intensity Modulated Radiation Therapy Planning And Delivery Of Early-Stage Non-Small Cell Lung Cancer, Ilma Xhaferllari

Electronic Thesis and Dissertation Repository

Stereotactic ablative body radiotherapy (SABR) is the standard of care for inoperable early-stage non-small cell lung cancer (NSCLC) patients. However, thoracic tumours are susceptible to respiratory motion and, if unaccounted for, can potentially lead to dosimetric uncertainties. Respiratory gating is one method that limits treatment delivery to portions of the respiratory cycle, but when combined with intensity-modulated radiotherapy (IMRT), requires rigorous verification. The goal of this thesis is to optimize respiratory gated IMRT treatment planning and develop image-guided strategies to verify the dose delivery for future early-stage NSCLC patients.

Retrospective treatment plans were generated for various IMRT delivery techniques, including …

High Resolution Tropospheric Studies With An Mst Type Radar, Marcial Garbanzo-Salas

Electronic Thesis and Dissertation Repository

Applications and results of a variety of studies carried out with the Costa Rican VHF profiler radar are included. This radar is unique because of the wide frequency bandwidth available (5 MHz). During the developing stages of the wind profiler radar new techniques of processing and radar engineering were used.

A thorough analysis of a data-dependent method (Capon's) commonly used in radar was carried out. This method is analyzed based on a reference established by Fourier theory. Disadvantages of using data-dependent methods with small filters were found. A small filter size will cause Capon's method to underestimate the number of …

Development Of A Small Animal Conformal Irradiator With Dual Energy X-Ray Computed Tomography Imaging For Kilovoltage Dosimetry, Michael D. Jensen

Electronic Thesis and Dissertation Repository

External beam radiotherapy has become technically sophisticated with image guided radiation therapy (IGRT) and intensity modulated radiation therapy (IMRT). These technologies allow for precise delivery of radiation to geometric targets in cancer patients. However, many questions remain on how to best define targets based on biological information, such as functional imaging, and how to combine radiation with other cancer therapies. To help answer these questions, small animal preclinical studies are needed to generate data to inform clinical trials. However, the precise radiation delivery capabilities of IGRT and IMRT have not been available in the preclinical labs. To enable translational experiments …

Stellar Spectroscopy: New Methods And Insights, Sanaz S. Golriz

Electronic Thesis and Dissertation Repository

The study of the chemical evolution of stars is of crucial importance since they play a major role in the enrichment of the chemistry of the universe. Throughout their lifetime, stars undergo several processes that can alter their chemistry. Gradually, the nucleosynthesis products from the interior of the star are radiatively and convectively levitated and mixed with the upper layers of the atmosphere. In the later stages of their evolution, low to intermediate mass stars (0.8-8.0~M☉) eject a significant fraction of these nucleosynthesis products, resulting in a circumstellar envelope of gas and dust around the central star with a very …

Fragmentation And Wake Formation In Faint Meteors: Implications For The Structure And Ablation Of Small Meteoroids, Edward Stokan

Electronic Thesis and Dissertation Repository

Meteors with peak magnitudes fainter than +2 are typically called faint meteors, resulting from the atmospheric entry and ablation of meteoroids less massive than 10^-4 kg. The processes of luminous wake formation and fragmentation, which occur during ablation, are poorly understood for faint meteors, and are important constraints for models of meteoroid structure. The goal of this work is to improve understanding of these processes through analysis of high-resolution intensified video observations, and creation of a detailed meteoroid ablation model.

In the first part of this work, thirty faint meteors observed with the Canadian Automated Meteor Observatory (CAMO) are …

Gravity Wave Spectra Morphology In The Arctic And Non-Arctic Lower Atmosphere, Melanie C. Wright

Electronic Thesis and Dissertation Repository

The spectral analysis of data from three VHF radars (one high-Arctic and two mid-latitudes) show support for the universal spectrum theory for gravity waves in the lower atmosphere (altitudes of 2.0-11.0 km), provided that the impact of the off-vertical beam and noise are taken into consideration. This analysis also reveals that local gravity wave generation is of secondary importance, but still significant for determining the spectra.

A total of eight spectral methods were considered and scrutinized for the purposes of determining gravity wave spectra from VHF radar data. A definition for the “best” method was given and examined. The method …

Advances In Image Acquisition And Filtering For Mri Neuroimaging At 7 Tesla, Andrew T. Curtis

Electronic Thesis and Dissertation Repository

Performing magnetic resonance imaging at high magnetic field strength promises many improvements over low fields that are of direct benefit in functional neuroimaging. This includes the possibility of improved signal-to-noise levels, and increased BOLD functional contrast and spatial specificity. However, human MRI at 7T and above suffers from unique engineering challenges that limit the achievable gains. In this thesis, three technological developments are introduced, all of which address separate issues associated with functional magnetic resonance neuroimaging at very high magnetic field strengths.

First, the image homogeneity problem is addressed by investigating methods of RF shimming — modifying the excitation portion …

Potential For Measurement Of Mesospheric Ozone Density From Overdense Meteor Trains With A Monostatic Meteor Radar, Reynold E. Sukara

Electronic Thesis and Dissertation Repository

Thermally ablating meteoroids, colliding with the Earth’s atmosphere, leave a high temperature trail containing extremely energetic metallic ions and electrons. A well recognized, but unresolved, anomaly associated with ambipolar diffusion of meteor trains, which is more dominant in overdense meteors, takes place in the initial post-adiabatic train expansion. In this work, a newly proposed mechanism explaining this anomaly involves hyperthermal chemical reactions is presented. Data from the SKiYMET meteor radar system, deployed at latitudinally dispersed locations, were used to determine ozone density in the upper atmosphere by analyzing diffusion of overdense meteor trains. The results obtained in this study are …

The Impact Of Lateral Electron Disequilibrium On Stereotactic Body Radiation Therapy Of Lung Cancer, Brandon Disher

Electronic Thesis and Dissertation Repository

Stereotactic Body Radiation Therapy (SBRT) is an effective treatment option for patients with inoperable early-stage lung cancer. SBRT uses online image-guidance technology [e.g. cone-beam CT (CBCT)] to focus small-fields of high energy x-rays onto a tumour to deliver ablative levels of radiation dose (e.g. 54 Gy) in a few treatment fractions (e.g. 3). For the combination of these treatment parameters and a low density lung, lateral electron disequilibrium (LED) can potentially occur, reducing lung and tumour doses. The goal of this thesis was to determine the impact of LED on stereotactic body radiation therapy for lung cancer.

The effect of …

Accelerated Imaging Techniques For Chemical Shift Magnetic Resonance Imaging, Curtis N. Wiens

Electronic Thesis and Dissertation Repository

Chemical shift imaging is a method for the separation two or more chemical species. The cost of chemical shift encoding is increased acquisition time as multiple acquisitions are acquired at different echo times. Image acceleration techniques, typically parallel imaging, are often used to improve the spatial coverage and resolution. This thesis describes a new technique for estimating the signal to noise ratio for parallel imaging reconstructions and proposes new image reconstructions for accelerated chemical shift imaging using compressed sensing and/or parallel imaging for two applications: water-fat separation and metabolic imaging of hyperpolarized [1-¹³C] pyruvate.

Spatially varying noise in …

Implementation,Validation And Application Of An Automated Motion Correction Algorithm In Hepatic Perfusion Ct For Image-Guided Radiotherapy, Nikolaj Kg Jensen

Electronic Thesis and Dissertation Repository

Functional imaging holds promise in guiding, evaluating and predicting efficacy of cancer treatment. Perfusion imaging provides high resolution functional information generated by applying a model to a dynamic series of contrast enhanced anatomical images.

The objectives of this thesis are: 1) to develop and validate a registration algorithm to reduce breathing motion artifacts in hepatic perfusion CT, and 2) to evaluate the potential of perfusion CT to improve radiotherapy of liver cancer.

An automated one-dimensional correlation-based registration algorithm was developed and validated in phantom and pig studies and against manual registration of patient scans. This algorithm was used to register …

Simultaneous Radar And Video Meteors, Robert J. Weryk

Electronic Thesis and Dissertation Repository

The goal of this thesis is to better understand the physical and chemical properties of meteoroids by using simultaneous radar and video observations of meteors. The Canadian Meteor Orbit Radar (CMOR) and several Gen-III image-intensified CCD cameras were used to measure common meteors and validate metric errors determined through Monte Carlo modelling and to relate radar electron line density (q) to video photon radiant power (I). By adopting an ionisation coefficient from Jones (1997) and using recorded measurements of q/I, a corresponding estimate of the fraction of meteoroid kinetic energy loss converted into light (luminous efficiency) was found.

It was …

Hyperpolarized Noble Gas Magnetic Resonance Imaging And Dynamic Spectroscopy For Investigation Of Rat Models Of Lung Inflammation, Matthew S. Fox

Electronic Thesis and Dissertation Repository

Imaging of the lungs using non-ionizing approaches such as hyperpolarized ³He and ¹²⁹Xe magnetic resonance imaging (MRI) is a useful tool both for research and clinical applications. This work focused on development of ¹²⁹Xe MRI techniques to investigate inflammation in rat lungs. A rodent model of inflammation, specifically radiation-induced lung injury (RILI) was developed using a collimated ⁶⁰Co source. A quantitative MRI technique measuring absolute ventilated lung volume (|VLV|) was performed using ¹²⁹Xe and ³He. Following a comparison between |VLV| values obtained from rats using the previously established ³He method and those obtained …

High Power Systems For Dynamic Field Control And Shielding In The Mr Environment, Dustin W. Haw

Electronic Thesis and Dissertation Repository

This thesis addresses several aspects of gradient and shim coil design and fabrication. New design techniques are coupled with experimental construction methods to expand small animal insert gradient and shim technology. The design techniques are also applied to other areas of magnetic resonance hardware.

A custom 2-axis gradient insert coil is designed and fabricated for the purpose of eddy current characterization. The construction tolerances were examined via bench top inductance measurements and eddy currents measurement inside a 7.0 T head-only MR system. A great deal of freedom is available when positioning shielding coils with respect to their corresponding primary coils …