September 25, 2023
17:00
Louvain-la-Neuve
Place Sainte Barbe, auditorium BARB91
For the degree of Doctor of Engineering Sciences and Technology
Despite the continuous improvement of prevention and treatments, cardiovascular diseases are the most common cause of death in the world. They correspond to (micro)structural changes affecting the proper functioning of the cardiovascular system. To non-destructively assess the complex and heterogeneous 3D structural organization of the heart and its constituents (heart chambers, coronary blood vessels, muscle fibers and heart valves), advanced imaging techniques are required.
This thesis was dedicated to the optimization and application of microfocus computed tomography (microCT)-based imaging techniques, such as contrast-enhanced computed tomography (CECT) and cryogenic CECT (cryo-CECT) to the entire heart (murine) and the heart valves (porcine and human). First, cryo-CECT, in which the biological samples are frozen and preserved frozen during the entire image acquisition, was optimized on bovine muscle samples to visualize individual muscle fibers. It was then applied to hypertrophic and control murine hearts to demonstrate the ability to perform 3D histopathology of biological samples. It allowed to compute the orientation and thickness of individual muscle fibers in the myocardium. Then, CECT and cryo-CECT were compared using two imaging qualities to perform 3D histology of healthy murine hearts. The microstructure of the coronary blood vessel network and the 3D thickness distribution of the left-sided heart valves were characterized in a non-destructive way.
In the second part of the PhD thesis, human calcified aortic valves (associated with aortic stenosis) were analyzed using high-resolution microCT (without contrast-enhancement) to quantitatively describe the calcifications present in the cusps, as well as the changes in the soft tissues surrounding the dense calcifications. This detailed microstructural characterization was obtained for two diagnosis groups and paves the way for a better understanding of the calcification mechanisms involved in aortic stenosis. Finally, CECT and cryo-CECT were applied to healthy porcine mitral valves to determine their microstructure in full 3D. While CECT surprisingly revealed the presence of adipocytes and a complex blood vessel network, cryo-CECT enabled the 
visualization of the organization of extracellular matrix fibers within the porcine mitral valve leaflet. Both techniques were finally applied to a chorda tendinea sample (connecting the mitral valve leaflet to the papillary muscle), and revealed the intricate transition from collagen towards muscle fibers.
Jury members :
- Prof. Greet Kerckhofs (UCLouvain, Belgium), supervisor
- Prof. Benoît Lengelé (UCLouvain, Belgium), supervisor
- Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
- Prof. Christophe Beauloye (UCLouvain, Belgium)
- Prof. Nele Famaey (KU Leuven, Belgium)
- Prof. Christophe De Vleeschouwer (UCLouvain, Belgium)
- Dr. Romain Capoulade (Université de Nantes, France)