X-ray Dark-Field Imaging Techniques

1. Brief description of the context of the research including potential impact

X-ray imaging is critical in the inspection of the inner structure of materials across a range of applications in manufacturing and security, as well as the diagnosis of disease in clinical settings. Whereas conventional X-ray imaging shows contrast primarily on the density of the sample, for materials with a lack of density inhomogeneities, superior contrast can be obtained when measuring the refraction and scattering of the X-rays. X-ray dark-field imaging is an approach that can show the strength of scattering from density variations with characteristic lengths on the scale of tens of microns. Measuring the X-ray dark-field signal requires a specialised setup, such as the Edge Illumination system employed at UCL. If density variations exist due to a fibrous structure, the directional sensitivity of the system allows the orientation of such fibres to be mapped.

2. Aims and Objectives

This project will centre around improving the capabilities of X-ray dark-field imaging on the Edge Illumination system. The objectives focus on improving the data acquisition and analysis for faster scan times and improving the information available from such scans.

The objectives are:
- Automatic alignment of system masks, decreasing expertise required to operate the system most efficiently
- "Single-Shot" dark-field imaging, where dark-field contrast can be acquired with a single exposure provided strict mask alignment
- Dark-field CT - reconstructing a 3D volume of the dark-field signal
- Directional dark-field imaging - with the ability to map the orientation of anisotropic fibrous scatterers within a sample
- Dark-field tensor tomography - reconstructing a full 3D volume of anisotropic scatterers

3. Novelty of the Research Methodology

Previous research has been carried out into mask alignment in an Edge Illumination system, however, no automatized method has been implemented. Single-shot phase-contrast images are currently under investigation; however, this has not been investigated for dark-field contrast. Dark-field CT, directional dark-field and dark-field tensor tomography have all been implemented on a different x-ray setup, but yet to be investigated on an Edge Illumination system which would potentially overcome some limitations in the previous approaches.

4. Alignment to EPSRC's strategies and research areas

This project aligns with the EPSRC Healthcare Technologies and Engineering strategies. New x-ray imaging techniques can improve the ability to diagnose disease in Medical Imaging, or the quality of material production in Manufacturing Technologies and Materials Engineering.

5. Any Companies or Collaborators Involved

None at present, however if successful this project could be brought to Nikon Metrology, who are currently developing an Edge Illumination XPCi system.