Conversion of a proton pair para order into 13C polarization by rf irradiation, for use in MRI

We describe the theory of production of hyperpolarized 13C in small organic molecules, for use as molecular contrast agents in MRI, by a two-step process. The first is a catalyzed hydrogenation with para-hydrogen in a small dc magnetic field under rf irradiation, resulting in a molecular proton pair in the pure para state. The second step converts this para order into net hyperpolarization of a nearby carbon 13 through a sequence of rf pulses at the resonance frequencies of both spin species. The final theoretical polarization is close to unity. The whole process, which was successfully implemented, takes a few seconds. To cite this article: M. Goldman, H. Jóhannesson, C. R. Physique 6 (2005).