Yoshihara, H.A., et al., High-field dissolution dynamic nuclear polarization of [1-(13)C]pyruvic acid. Phys Chem Chem Phys, 2016. 18(18): p. 12409-13.
http://www.ncbi.nlm.nih.gov/pubmed/27093499
[1-(13)C]pyruvate is the most widely used hyperpolarized metabolic magnetic resonance imaging agent. Using a custom-built 7.0 T polarizer operating at 1.0 K and trityl radical-doped [1-(13)C]pyruvic acid, unextrapolated solution-state (13)C polarization greater than 60% was measured after dissolution and rapid transfer to a spectrometer magnet, demonstrating the signal enhancement attainable using optimized hardware. Slower rates of polarization under these conditions can be largely overcome with higher radical concentrations.