ORCID
https://orcid.org/0009-0007-8269-1923
Date of Award
Spring 2025
Language
English
Embargo Period
5-3-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
College/School/Department
Department of Physics
Program
Physics
First Advisor
Carolyn A. MacDonald
Second Advisor
Jonathan C. Petruccelli
Committee Members
Ariel Caticha, Alexander Khmaladze, Noor Mail
Keywords
Computed Tomography, X-ray Phase CT, Dark Field CT, Attenuation CT, SNR, Edge Enhancement
Subject Categories
Optics | Physical Sciences and Mathematics | Physics
Abstract
Conventional computed tomography produces a 2D slice or 3D image from multiple conventional images to avoid overlapping structures and increase visualization of the internal features of the object. A set up, macro controls and processing for computed tomography was created for the Center for X-ray Optics for the first time, and demonstrated in this work. Adding differential phase contrast to conventional x-ray images highlights edges. Two more channels of information, dark field and integrated phase, improve the contrast and increase the signal-to-noise ratios of the image. Combining these channels with computed tomography is an important development. This work is the first demonstration of phase and dark field tomography for the Center.
Mesh-based x-ray phase imaging is a technique used to extract five computed channels: computed attenuation along with vertical and horizontal dark field and differential phase contrast images. The integrated phase image is computed from the differential phases. A periodic, metal, inexpensive mesh is employed to visualize the distortion of the x-ray beam when a sample present. Fourier transform techniques are utilized to produce those channels. A simple set up was developed to demonstrate computed attenuation, dark field and phase x-ray CT. The signal-to-noise ratios were quantified for the first time for mesh-based CT with a conventional source. The SNR for a strong scatterer was demonstrated to be a factor of 10 higher than the attenuation contrast for a slice through a CT image.
Geometric-flow x-ray phase imaging (also known as optical-flow) is another method used in this research for phase reconstruction and combined with computed tomography to produce a phase channel in addition to the conventional CT. This may be the first demonstration of this technique with a conventional, large spot, source. The differential phase images in orthogonal directions map the deformation of the reference pattern. A wire mesh or sandpaper can be used as a reference pattern in the optical-flow technique. The quality of the differential phase x-ray computed tomography was measured for the first time, by edge enhancement and the signal-to-noise ratio SNR. Optimization experiments were performed for the edge enhancement by varying the x-ray voltage and adjusting the distance between the sample to the detector. Similarly, the contrast SNR was examined versus the exposure time for the integrated phase CT.
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Allahyani, Wadiah Hamed, "Demonstration and Assessment of Dark Field and Phase X-ray Computed Tomography" (2025). Electronic Theses & Dissertations (2024 - present). 183.
https://scholarsarchive.library.albany.edu/etd/183
