The theory and practice of hyperpolarization in magnetic resonance using parahydrogen

In this review we have aimed to comprehensively and critically report on the literature descriptions of the polarization transfer and the subsequent evolution of magnetic states resulting from the addition of parahydrogen to inorganic systems and unsaturated organic hydrogen acceptors. In doing so, we have covered evolution under high and low field and thus both the weak and strong coupling regimes. Low field evolution experiments have been shown to generate polarization transfer to coupled heteronuclei. This technological advance has enabled the collection of high sensitivity in vivo 13C-MRI measurements and marks a major opportunity for future development. It has also been illustrated how parahydrogen has enabled the achievement of a greater understanding of both homogeneous and heterogeneous catalysis.While early studies were limited to the detection of metal-dihydrides, sensitization of the substrate when hosted within the coordination sphere of the metal has dramatically widened applicability of the tec. The observation of one-proton PHIP, while as yet relatively unexplored, presents an area which is ripe for further investigation. The exciting discovery of non-hydrogenative PHIP, referred to as signal amplification by reversible exchange, demonstrates the potential for parahydrogen to polarize any substrate under the right conditions. Research involving parahydrogen now involves a large range of international researchers, and continued expansion of the field over the next few years seems assured. The possibility of creating a new generation of low field MRI systems using novel detection methods in conjunction with hyperpolarized molecules presents an opportunity to develop low-cost screening capabilities which could be far more widely accessible than those associated with more traditional 1.5 T clinical MRI scanners. Near-zero field measurements employing parahydrogen-derived spin systems have already been successfully completed. © 2012 Elsevier B.V. All rights reserved.