MUST - A compact multimodal X-ray system for 3D micro-imaging of soft tissue based on the integration of spectral and phase-contrast techniques

Abstract:

This research proposal aims at developing innovative imaging protocols delivering X-ray spectral phase-contrast 3D images at the micrometer scale of soft tissue samples on the centimeter scale. The project builds on a compact micro-computed tomography (μCT) system available in Trieste leveraging on a unique integration of two enabling technologies: a chromatic X-ray detector and the edge-illumination phase-contrast technique. Each of the two innovative technologies guarantees substantial advantages compared to conventional X-ray imaging. Chromatic detectors allow for X-ray spectral imaging (XSI), thus generating material-specific quantitative maps. Edge-illumination (EI) phase-contrast imaging (XPCI) allows for the extraction of phase-shift and dark-field signals, corresponding to enhanced visibility of soft tissues and highly-granular structures.

The laboratory system was initially developed pursuing maximum flexibility, enabling multi-modal and multi-scale imaging in a wide energy range (40 - 100 kV). This project will specialize the setup, targeting maximum performance in spectral, phase, and dark-field signal sensitivity at a virtual histology-compatible spatial resolution (⪅10 μm). The target will be reached by developing imaging protocols in each of the following modalities:

1. Spectral CT, performing single-shot acquisitions by setting the two chromatic detector thresholds, yielding, e.g., iodine-base contrast-agent 3D maps at resolutions from 20 to 50 μm with fields-of-view (FOVs) from 1.5 to 4 cm.
2. Phase-contrast Dark-field CT, through EI, yielding phase and dark-field maps at a tunable resolution from 5 to 50 μm and 2 cm FOV.
3. Hybrid Spectral - Phase-Contrast CT, by operating the detector in two thresholds mode and acquiring EI images, delivering combined spectral and phase material decomposition.

Additionally, a next-generation fully-spectral detector - Timepix4 - will be integrated into the system. This will enable the implementation of an innovative, simpler, and scalable XPCI geometry (beam-tracking), also allowing post-acquisition energy binning and improving spectral performance. This beyond-state-of-the-art implementation will bring the setup to a world-leading position among compact XPCI systems.

The proposed techniques will improve soft-tissue discrimination capabilities compared to state-of-the-art table-top μCT dedicated to non-destructive 3D imaging of biological samples. The target applications driving this initiative are in the fields of (i) characterization of 3D-printed scaffolds for osteochondral tissue regeneration and (ii) study of osteoarticular disease development through innovative cationic contrast agents labeling cartilage structures.

The project's ultimate goal is to obtain high-quality results with a single, cheap, compact, and non-destructive lab device adding to, or as informative as, those obtained with time-consuming/destructive techniques (e.g., histology, TEM, SEM).