How to design 13C para-hydrogen-induced polarization experiments for MRI applications

The application of hyperpolarization techniques for MRI purposes is gathering increasing attention, especially for nuclei such as 13C or 129Xe. Among the different proposed methods, ParaHydrogen Induced Polarization requires relatively cheap equipment. The setup of an MRI experiment by means of parahydrogen requires the application of skills and methodologies that derive from different fields of knowledge. The basic theory and a practical insight of this method are presented here. Parahydrogenation of alkynes, having a labelled 13CO group adjacent to the triple bond, catalyzed by Rh(I) complexes containing a chelating phosphine, represents the best choice for producing and maintaining high heteronuclear polarization effect. In order to transform anti-phase into in-phase (net) 13C polarization for MRI application it is necessary to set up the described magnetic field cycle procedure. In vitro and in vivo images have been acquired using fast imaging sequences (RARE and trueFISP).