# X-ray differential phase contrast imaging on asymmetric dual-phase grating interferometer with source grating: theory and experiment

## TL;DR

This paper develops a wave optics-based theoretical framework for designing asymmetric dual-phase grating X-ray interferometers with source gratings, validated through numerical and experimental studies, improving dose efficiency in medical imaging.

## Contribution

It introduces a comprehensive wave optics analysis and a geometrical explanation for dual-phase grating X-ray systems, aiding design optimization especially with large focal spot sources.

## Key findings

- Theoretical framework accurately predicts system behavior.
- Experimental results confirm the theory's validity.
- Design guidelines improve dose efficiency in X-ray imaging.

## Abstract

Recently, the dual-phase grating based X-ray differential phase contrast imaging technique has shown better radiation dose efficiency performance than the Talbot-Lau system. In this paper, we provide a theoretical analyses framework derived from wave optics to ease the design of such interferometer systems, including the inter-grating distances, the diffraction fringe period, the phase grating periods, and especially the source grating period if a medical grade X-ray tube with large focal spot is utilized. In addition, a geometrical explanation of the dual-phase grating system similar to the standard thin lens imaging theory is derived with an optical symmetry assumption for the first time. Finally, both numerical and experimental studies have been performed to validate the theory.