Sensitivity enhancement in Magnetic Resonance by means of para-hydrogen (pH2) – PH2MR

The major objective of this project is sensitivity enhancement in magnetic resonance and more especially in MRI (Magnetic Resonance Imaging). The use of parahydrogen constitutes a promising method. This is because a hydrogenation reaction carried out with para-enriched gaseous hydrogen (di-hydrogen possesses two spin isomers: ortho and para) leads to a product, the resonances (those arising from hydrogenation) of which are enhanced by several orders of magnitude (greater is the enrichment, greater is the enhancement). In fact, these resonances show up generally in the form of antiphase doublets and are not directly usable for the sensitivity increase of NMR (Nuclear Magnetic Resonance) and MRI experiments. We are the only French group working on this subject and we have shown recently that, under particular experimental conditions, it was possible to obtain a net polarization leading to in-phase resonances. In this case, the term “hyperpolarization” becomes meaningful. The original part of the present project rests on this new approach which will have to be assessed by numerous NMR spectroscopy experiments. In particular, transfer of this hyperpolarization toward molecules dedicated to specific applications will be envisioned by means of intermolecular nuclear Overhauser effect. This methodology will rest on new substrates prone to be hydrogenated (initiators) and to appropriate targets (dedicated molecules). Both types of molecules will be synthesized and thoroughly tested. A parahydrogen enrichment unit (for an enrichment of about 100%) will be constructed. In a more prospective way, we shall try to devise vessels in which the para-ortho conversion is slowed down. Besides MRI of materials and in vivo MRI, applications will concern i) the sensitivity improvement of NMR in weak magnetic fields and, more tentatively, of nitrogen-14 Nuclear Quadrupole Resonance (NQR; magnetic resonance in zero magnetic field for indentifying nitrogen containing molecules), ii) the depolarization as a function of the NMR magnetic field value (relaxometry).