Design of experiments to optimise the staining protocol of polyoxometalates for contrast-enhanced microCT of aorta tissue

Details

Supervisors

Kerckhofs, Greet ; Hoffmann, Delia

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil biomédical, à finalité spécialisée

Abstract

Vascular diseases are one of the leading causes of death in developed countries. To better treat these diseases, a complete characterisation of the spatial organisation and mechanical properties of tissues is needed. This can be achieved by using microfocus X-ray tomography, and in particular contrast-enhanced microfocus tomography. This novel 3D histology technique is based on the use of contrast agents when visualising soft tissue, such as vasculature. Recently, two new contrast agents have shown promise in this field: Hf-WD 1:2 POM and Mono-WD POM. However, there is a great lack of fundamental knowledge about the properties of these contrast agents. The general aim of this master thesis was to characterise these two contrast agents in terms of the contrast they offer and their diffusion within a tissue. To do so, both molecules were used on porcine aorta during experiments during which different parameters were varied: the mass percentage of the contrast agent in solution, the volume of the solution and the staining time. To carry out this study in a judicious way, two design of experiments were performed. The results revealed that the two molecules behave differently, particularly since Hf-WD 1:2 POM mainly separated into Hf-WD 1:1 POM and Mono-WD POM. The latter offered a lower contrast enhancement than Hf-WD 1:1 POM, but it diffused considerably more rapidly within the tissue. Moreover, the study demonstrated that increasing the mass percentage of contrast agents is the most important condition for improving contrast enhancement and diffusion. Furthermore, although all analyses were performed in the media, a microstructural difference between distinct regions of the tissue could be highlighted. The side of the media exposed to the adventitia showed greater contrast enhancement but slower diffusion compared to the side exposed to the intima. High-quality scans and conventional 2D histology revealed that this was probably linked to a higher presence of elastin fibres in the tissue. In conclusion, this master thesis is a first step in the study of these two contrast agents, and has highlighted the benefit of design of experiment. Further research is required, particularly regarding the binding mechanism of the molecules in biological tissue. Another contrast agent, Hf-WD 2:2 POM, should also be investigated. Finally, biomechanical tests should be performed.