Comparison of different polyoxometalates for their staining potential in contrast-enhanced computed tomography

Details

Supervisors

Kerckhofs, Greet

Faculty

Ecole polytechnique de Louvain

Degree label

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

Abstract

The microscopic 3D visualization of biological tissue is crucial for understanding organ function and how they are affected by diseases and aging. The demand for high-resolution 3D imaging methods in histopathology has driven the development of new microscopic imaging techniques. In this context, X-ray microfocused computed tomography (microCT) has emerged as an advantageous solution, offering remarkable spatial resolution while remaining cost-effective. However, although the method provides excellent results when imaging dense tissues (e.g., bone), it is limited by the low X-ray attenuation properties of soft tissues. To overcome this limitation, contrast-enhanced staining agents (CESAs) were introduced. They passively diffuse within tissues and preferentially bind to specific tissue components, thereby improving the contrast for soft tissue imaging, a technique referred to as contrast-enhanced computed tomography (CECT). This master's thesis focuses on the use of polyoxometalates (POMs) as CESAs for CECT imaging, building on the encouraging results reported by G. Kerckhofs' research group in this field. The goal of this master’s thesis was to compare the performance of four promising POMs as CESAs for CECT imaging. Infra-renal porcine aorta samples were stained with Parent-WD, Mono-WD, Hf-WD 1:2, and Zr-WD 1:2 POMs to evaluate their ability to maintain tissue integrity, their diffusion behavior, and their effectiveness in producing contrasted images. Additionally, a production cost analysis was conducted with the aim to provide a comprehensive overview of each POM’s feasibility for use as a CESA in large-scale CECT applications within the biomedical field. Initial results indicated that none of the four studied POM affected tissue thickness, suggesting no tissue shrinkage or swelling. Diffusion behavior analysis identified Mono-WD POM as the fastest diffusing agent within tissue. While Zr-WD 1:2 POM stained tissue slightly faster than Hf-WD 1:2 POM, samples stained with Parent-WD POM were not fully stained even after 13 days. Regarding image contrast, Mono-WD POM produced low-contrast images, whereas Parent-WD POM yielded the highest grey values. Hf-WD 1:2 and Zr-WD 1:2 POMs performed slightly less well than Parent-WD POM in terms of image contrast. Cost analysis identified Parent-WD POM as the most affordable and scalable option, while the production of more complex POMs such as Hf-WD 1:2 and Zr-WD 1:2 POMs incurred significantly higher costs and presented greater challenges for upscaling. While this comprehensive analysis did not identify a single POM as the ideal candidate for optimized large-scale CECT imaging, it demonstrates that there remains room for further protocol optimization and investigation of POMs to better fit application specific scenarios.