Fig. 7.

a Representative ¹³C hyperpolarized (2° flip angle) and thermal (90° flip angle) NMR spectra of 2 mM [1-¹³C]pyruvic acid taken at 14.1 T and 298 K after dissolution of frozen polarized trityl-doped sample at 4.6 T and 1.15 K. The calculated liquid-state NMR signal enhancement is about 12,000-fold. b Decay of the liquid-state NMR signal emanating from hyperpolarized [1-¹³C]pyruvic acid at 14.1 T and 298 K. The decay curve was monitored by applying a 2° rf pulse every 2 s. These data were fitted with a decay equation accounting for the effects of rf pulse and T₁ relaxation [29]