Efficient 13C-hyperpolarization of lactate using parahydrogen and proton exchange.

Hyperpolarization of biological molecules1,2,3 is a promising approach for metabolic MR imaging. Hyperpolarization methods based on parahydrogen and proton exchange4,5 promise almost universal polarization of many molecules, but current polarization yields are relatively low. Here, we present a new variant of Parahydrogen-Induced Polarization relayed via proton exchange (PHIP-X), which we demonstrate using the important biomolecule lactate. Polarization transfer between labile and covalent bound protons at different fields, combined with an RF pulse sequence, enables significantly enhanced 13C polarization of lactate. We believe that this approach may be used as a general strategy for the polarization of various biomolecules.