X-ray Interferometry Using a Modulated Phase Grating: Theory and Experiments

TL;DR

This paper develops a theoretical framework for X-ray modulated phase grating interferometry, validating it through experiments that demonstrate its capability to produce high-quality attenuation, phase contrast, and dark-field images.

Contribution

It introduces a Fourier optics-based theory for MPG interferometry with a 2D staggered grating and compares predictions with experimental results.

Findings

Theoretical and experimental fringe visibility match well.

Quantitative imaging of porous materials achieved.

Qualitative dark-field imaging of biological samples demonstrated.

Abstract

X-ray grating interferometry allows for the simultaneous acquisition of attenuation, differential-phase contrast, and dark-field images, resulting from X-ray attenuation, refraction, and small-angle scattering, respectively. The modulated phase grating (MPG) interferometer is a recently developed grating interferometry system capable of generating a directly resolvable interference pattern using a relatively large period grating envelope function that is sampled at a pitch that allows for X-ray spatial coherence using a microfocus X-ray source or by use of a source G0 grating that follows the Lau condition. We present the theory of the MPG interferometry system for a 2-dimensional staggered grating, derived using Fourier optics, and we compare the theoretical predictions with experiments we have performed with a microfocus X-ray system at Pennington Biomedical Research Center, LSU. The theoretical and experimental fringe visibility is evaluated as a function of grating-to-detector distance. Quantitative experiments are performed with porous carbon and alumina samples, and qualitative analysis of attenuation and dark-field images of a dried anchovy are shown.