Date of Award

1-1-2015

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Physics

Content Description

1 online resource (ix, 61 pages) : color illustrations.

Dissertation/Thesis Chair

Carolyn A MacDonald

Committee Members

Carolyn A MacDonald, Muhammad S Alam, Ariel Caticha, Jonathan Petruccelli, Jahangir Satti

Keywords

Contrast, Diffraction phase, Grid imaging, Mesh grid, Phase, Scattering image, Phase-contrast microscopy, Contrast media (Diagnostic imaging), Breast, Fourier transform spectroscopy

Subject Categories

Physics | Radiology

Abstract

Low contrast in x-ray attenuation imaging between different materials of low electron density is a limitation of traditional x-ray radiography. Phase contrast imaging offers the potential to improve the contrast between such materials, but due to the requirements on the spatial coherence of the x-ray beam, practical implementation of such systems with tabletop (i.e. non-synchrotron) sources has been limited. One recently developed phase imaging technique employs multiple fine-pitched gratings. However, the strict manufacturing tolerances and precise alignment requirements have limited the widespread adoption of grating-based techniques. In this work, we have investigated a technique recently demonstrated by Bennett et al.1 that utilizes a single grid of much coarser pitch. Our system consisted of a low power 100 µm spot Mo source, a CCD with 22 µm pixel pitch, and either a focused mammography linear grid or a stainless steel woven mesh. Phase is extracted from a single image by windowing and comparing data localized about harmonics of the grid in the Fourier domain. A Matlab code was written to perform the image processing. For the first time, the effects on the diffraction phase contrast and scattering amplitude images of varying grid types and periods, and of varying the window function type used to separate the harmonics, and the window widths, were investigated. Using the wire mesh, derivatives of the phase along two orthogonal directions were obtained and new methods investigated to form improved phase contrast images.

Download

Share

COinS