Masters Theses

Date of Award

5-2021

Degree Type

Thesis

Degree Name

Master of Science

Major

Biomedical Engineering

Major Professor

Jacqueline A. Johnson

Committee Members

Jacqueline A. Johnson, Russell L. Leonard, Feng-Yuan Zhang

Abstract

Digital radiography (DR) is an important two-dimensional imaging technique in the field of medicine that utilizes x-rays to form a digital image. DR employs a flat panel detector that converts incident x-rays, that have passed through the subject, to an electrical signal, which is used to create a digital image. The conversion from x-rays to electrical signals can be done either directly or indirectly. The direct method involves the x-rays being converted to an electrical signal via an array of semiconductors. The indirect method utilizes scintillators to absorb the x-rays and produce light in the visible spectrum, which is then collected by photodiodes and converted to an electrical signal. One issue that many modern flat panel detectors have is reduced efficiency due to a significant percentage of the incident x-rays passing through the detector without being absorbed. In order to raise the efficiency of these flat panel detectors, rare earth-doped scintillating glass ceramics have been proposed to replace the traditional non-scintillating borosilicate substrates that support the detector electronics. Two series of glass-ceramic scintillators were investigated for this purpose. The first series investigated the potential of calcium fluoride as a scattering center, as well as how the calcium fluoride luminescence behaved when doped with europium. The second series investigated the use of cerium as a sensitizer to improve the scintillating efficiency of terbium. Both series showed that the scattering and luminescent properties of the materials can be controlled. Scintillating glass ceramic materials have the potential to become viable replacements for the un-doped borosilicate substrates that are used in modern flat panel detectors.

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