Degree

Doctor of Philosophy (PhD)

Department

Physics & Astronomy

Document Type

Dissertation

Abstract

We investigated a novel analyzer-less X-ray interferometer with a spatially modulated phase-grating (MPG) which produces three types of images (attenuation image, phase image and scatter image) for Breast computed tomography (CT). The system provides the three complimentary X-ray images with the goals of limiting the dose to the object and achieving similar attenuation image sensitivity as a standard absorption-only Breast CT. The MPG system features an X-ray source, a source-grating, a single phase-grating, and a detector. No analyzer grating is necessary, compared to other geometries such as Talbot-Lau X-ray interferometry (TLXI). Thus, there is a ~2 times improvement in X-ray fluence at the detector for our system compared to a same source-detector distance for TLXI, which requires an analyzer grating. In this work we investigated with simulation an MPG Breast CT system to determine if such a system geometry is clinically feasible. First the MPG was conceptually designed and evaluated via Sommerfeld-Rayleigh diffraction integral simulations. Next, we investigated source coherence requirements, fringe visibility, and dependence of phase sensitivity on different system parameters, for a proposed system geometry that should clinically feasible in terms of patient dose. The phase sensitivity of MPG interferometry was proportional to object-detector distance and inversely proportional to the period of broad fringes at the detector, which was determined by grating spatial modulation period. In our simulations, the MPG interferometry achieved 27% fringe visibility for a clinically realistic Breast CT geometry that used a source-detector distance of 950 mm and source-object distance of 500 mm. In conclusion, we simulated a promising analyzer-less X-ray interferometer for Breast CT, which uses a novel spatial sinusoid modulated phase-grating (MPG). Our system is expected to deliver attenuation, phase and scatter images in a single acquisition, with image quality and patient dose that is comparable to general Breast CT.

Date

4-8-2020

Committee Chair

Dey, Joyoni

Available for download on Wednesday, March 15, 2023

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