Laboratory-based x-ray microtomography with directional dark-field sensitivity

TL;DR

This paper introduces a compact laboratory x-ray microtomography system that uses directional dark-field sensitivity to reveal microstructural features and anisotropy in samples, providing complementary information to traditional imaging methods.

Contribution

The authors develop and validate a simple, robust 2-directional beam tracking method for dark-field x-ray tomography that captures anisotropic scattering with a single exposure.

Findings

Successfully imaged biological tissues and composites revealing microstructural details.

Demonstrated sensitivity to scattering anisotropy along two orthogonal directions.

Provided complementary information to attenuation and phase tomography.

Abstract

We demonstrate dark-field x-ray microtomography in a compact, laboratory-based system capable of resolving attenuation, phase, and anisotropic scattering signals with micrometer-scale resolution across centimetre-scale samples. The method is based on two-directional beam tracking (2DBT), which requires only a single optical element and is compatible with standard x-ray sources and detectors. We validate the system's capabilities through imaging of a custom-built phantom, a fibre-reinforced composite and ex-vivo biological tissues, including a bovine intervertebral disc, a rat heart, and a porcine meniscus. The results show that dark-field tomography provides complementary information to attenuation as well as to phase tomography, by revealing sub-resolution features such as fibre orientation and microstructural heterogeneity at length scales that are well below the voxel size. A key element of our system is its sensitivity to scattering along two orthogonal directions in the image plane, enabling the measurement of scattering anisotropy with a single exposure. As well as simple and robust, our approach is sensitive and precise. These findings demonstrate the potential of 2DBT for non-destructive and three-dimensional structural characterisation of samples and materials in engineering, materials science and biomedical applications.