Date of Award

1-1-2021

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Physics

Content Description

1 online resource (v, 81 pages) : illustrations (some color)

Dissertation/Thesis Chair

Carolyn MacDonald

Committee Members

Jonathan Petruccelli , Keith Earle, Alexander Khmaladze, Wu Liu

Keywords

Focusing polycapillary optics, Mesh-based X-ray phase imaging, Orthovoltage therapy, Propagation-based X-ray phase imaging, Quantitative phase retrieval, X-ray, X-ray optics, Diagnostic imaging, Radiotherapy, Phase-contrast microscopy

Subject Categories

Optics | Physics | Radiology

Abstract

Focusing polycapillary optics yield high gains in intensity and increased spatial resolution for a variety of clinical, lab-based, synchrotron, or in situ analysis applications. In this dissertation we investigate the extension of two applications of focusing polycapillary optics. The first is the application of polycapillary optics in radiation therapy. This discussion includes measurements and calculation of dose for focused beam orthovoltage therapy. A system has been designed to investigate whether the polycapillary optics can produce an X-ray beam which can give more accurate dose painting due to the higher dose concentration at the focal spot. X-ray exposures were measured with radio sensitive film. The measured spectrum of the X-ray beam was used to calculate the dose and compared with the measured dose on the films. The second application is medical imaging and quantitative phase retrieval. X-ray phase imaging can display subtle differences in low-density materials more readily than conventional X-ray imaging. However, due to spatial coherence requirements on the X-ray source, producing X-ray phase images has traditionally required either highly specialized sources, such as synchrotrons or small and low power microfocus sources, or multiple exposures with several carefully stepped precision gratings. To find appropriate approaches for enabling X-ray phase imaging in a clinically meaningful way, two techniques were tested. First, focusing polycapillary optics were applied in this work with conventional X-ray sources to enable propagation-based X-ray phase imaging. Quantitative phase retrieval was compared for two simple computational algorithms. Second, mesh-based X-ray phase imaging was demonstrated. In this technique, a simple, low-cost, coarse wire mesh and simple processing relaxes the spatial coherence constraint and allows quantitative phase retrieval. The mesh-based system combined with polycapillary optics significantly improved the accuracy of quantitative phase retrieval.

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