Physics Commons^™

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 …