Exploring contrast-enhancing staining agents for contrast-enhanced computed tomography imaging by Tim BALCAEN

For the degree of Doctor of Engineering Sciences and Technology

The need for high-resolution 3D imaging of biological tissues is a driving force behind the development of innovative technologies. Among these technologies, microfocus computed tomography (MicroCT) stands out for its exceptional spatial resolution, user-friendliness, and cost-effectiveness. While MicroCT excels at providing non-destructive 3D views of tissue samples, it is limited to visualizing dense tissues, such as bone, that strongly interact with X-rays.

To address this limitation, researchers have developed methods to enhance the contrast of soft tissues. The approach studied and discussed in this dissertation focuses on the use of heavy atom-containing molecules, known as contrast-enhancing staining agents (CESAs). These molecules passively diffuse into an ex vivo biological tissue sample and disperse throughout the tissues based on their affinity, contributing to improved tissue contrast. This specific methodology is also called contrast-enhanced computed tomography (CECT).

Within this thesis, a series of case studies were conducted to shed light on the staining mechanisms and diffusion kinetics of both established and novel CESAs for 3D histopathology of biological tissues. The primary focus was on investigating the chemistry and interactions of these staining systems, with each case study centered on a specific tissue or organ. In the first project, we explored the potential of CECT in revealing the microstructure of healthy murine brain hemispheres, as well as in murine disease models of Alzheimer’s disease and multiple sclerosis. The second project involved screening various CESAs for the study of adipose tissue in the bone marrow and muscle. Additionally, the staining mechanism of Lugol’s iodine components with respect to biological tissues was investigated using both simplified and more complex model systems. The third project centered on studying the diffusion kinetics of different types of polyoxometalates (POMs) through the porcine aorta wall.

In summary, this thesis has provided invaluable insights into the staining kinetics and mechanisms of CESAs for biological tissues. Furthermore, it has introduced novel CESAs into various fields of CECT, paving the way for further advancements in CESAs for 3D histopathology of biological tissues using CECT.

Jury members :

• Prof. Greet Kerckhofs (UCLouvain, Belgium), supervisor
• Prof. Wim De Borggraeve (KU Leuven, Belgium), supervisor
• Prof. Elke Debroye (KU Leuven, Belgium), chairperson
• Prof. Catherine Behets (UCLouvain, Belgium)
• Prof. Mario Smet (KU Leuven, Belgium)
• Prof. Mark Grinstaff (Boston University, Boston, US)
• Dr. Nada Savic (KU Leuven, Belgium)