Screening staining agents for contrast-enhanced microCT of vascular tissues: Assessing the effect on microstructural and mechanical properties

Cardiovascular tissues possess a complex microstructure, which remodel and adapt due to ageing and diseases. This complex and evolving microstructure is intrinsically linked to the tissue’s mechanical properties. To better understand how changes in the microstructure can impact the mechanical behavior, 4D-contrast-enhanced microCT (4D-CECT) can be used (i.e. in situ mechanical loading combined with 3D microstructural visualization). Since absorption-based CECT requires the use of contrast-enhancing staining agents (CESAs), we investigated six different CESAs for their suitability for 4D-CECT imaging of arterial tissue, considering their ability to provide good microstructural visualization and segmentation while ensuring the preservation of the mechanical properties. For this purpose, the penetration speed, contrast-enhancement, volume change, and stiffness change of porcine arterial tissue stained with the different CESA solutions were studied. Based on our results, we selected 1:2 Hafnium-substituted Wells-Dawson Polyoxometalate as the most suited CESA for 4D-CECT of arterial tissue. Phosphotungstic acid (PTA) and Lugol iodine with Sorensen’s buffer (Lugol), despite being the reference in the state-of-the-art as CESA and having excellent contrast-enhancement properties, were the only ones that significantly affected the mechanical properties of porcine arterial tissue. Additionally, for these two solutions, tissue shrinkage was observed, resulting in a volume reduction of approximately − 12 % for PTA and − 17 % for Lugol. Finally, it was observed that the penetration speed of all CESA solutions exhibited a ratio of 60–40 % from the intimal side to the adventitial side, which is likely due to the denser packing of elastic lamellae towards the adventitia. Overall, our study offers valuable new insights for selecting and comparing various CESA solutions for (4D-)CECT.