Masters Theses
Date of Award
5-2013
Degree Type
Thesis
Degree Name
Master of Science
Major
Biomedical Engineering
Major Professor
Jacqueline A. Johnson
Committee Members
Charles E. Johnson, Lino Costa
Abstract
Computed radiography is a standard medical imaging technology that uses photostimulable storage phosphor imaging plates to create an image. X-rays create electron hole pairs within the plate which recombine upon stimulation by a laser, producing light which is read out and stored as a digital image. Modern imaging plates contain an active layer of crystalline storage phosphors embedded in a polymer binder. The resolution of images from these plates is reduced due to light scattering at grain boundaries during readout. Fluorochlorozirconate (FCZ) glass-ceramic imaging plates containing BaCl2:Eu2+ [barium chloride] [europium]nanocrystals in the orthorhombic phase have been developed to decrease light scattering during readout and improve resolution for applications such as mammography where a high level of detail is required. However, these plates lack the conversion efficiency (CE) of current plates and therefore require a higher x-ray dose to provide sufficient light to produce an image. This work investigates the use of co-doping to increase the CE of FCZ glass-ceramic imaging plates.
A series of fluorochlorozirconate (FCZ) glass samples were produced, replacing the EuCl2 with HoF3 [holmium] to determine the effects of co-doping on light output. The samples were characterized using differential scanning calorimetry to determine the temperature at which orthorhombic BaCl2 crystallization occurs. Thermal treatments were performed to precipitate BaCl2 nanocrystals in the orthorhombic phase, creating a glass ceramic. The heat treated samples were characterized using phosphorimetry and x-ray diffraction to confirm the crystalline phases present. Photostimulated luminescence (PSL) experiments were conducted to evaluate light output. The results indicate that the addition of HoF3 increases the CE even though HoF3 singly doped FCZ glass ceramics do not exhibit any PSL.
In an effort to reduce the costs of the FCZ glass-ceramic imaging plates, experiments were conducted to see if less costly EuCl3 could be reduced to form the more expensive EuCl2 through heating in an inert atmosphere. Three different heating profiles were tested. The percent conversion was evaluated using Mössbauer [Mossbauer] spectroscopy. The results show that EuCl2 can be successfully synthesized from EuCl3.
Recommended Citation
Gray, Sharon, "An Investigation of Rare Earth Co-doping in Fluorochlorozirconate Glass-Ceramic Imaging Plates to Improve the Storage Phosphor Properties for Computed Radiography. " Master's Thesis, University of Tennessee, 2013.
https://trace.tennessee.edu/utk_gradthes/1621
Comments
The project described was supported by the National Science Foundation under Grant Number DMR1001381 and the National Institutes of Health under Grant Number 5R01EB006145- National Institute of Biomedical Imaging and Bioengineering. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Science Foundation,the National Institute of Biomedical Imaging and Bioengineering or the National Institutes of Health.