Magnetic Resonance Imaging (MRI) has a high importance in medicine as it enables the observation of the organs inside the body without the use of radiative or invasive techniques. However it is known to suffer from poor sensitivity. To circumvent this limitation, a key solution resides in the use of hyperpolarized species. Among the entities with which we can drastically increase nuclear polarization, xenon has very specific properties through its interactions with its close environment that lead to a wide chemical shift bandwidth. The goal is thus to use it as a tracer. This PhD thesis focuses on the concept of 129Xe MRI-based sensors for the detection of biological events. In this approach, hyperpolarized xenon is vectorized to biological targets via functionalized host systems, and then localized thanks to fast dedicated MRI sequences. The conception and set-up of a spin-exchange optical pumping device is first described. Then studies about the interaction of the hyperpolarized noble gas with new cryptophanes susceptible to constitute powerful host molecules are detailed. Also the implementation of recent MRI sequences optimized for the transient character of the hyperpolarization and taking profit of the xenon in-out exchange is described. Applications of this approach for the detection of metallic ions and cellular receptors are studied. Finally, our first in vivo results on a small animal model are presented.
Molecular MRI based on hyperpolarized xenon