Selective Excitation of [C]Bicarbonate Following Injection of Hyperpolarized [1-C]Pyruvate Allows for Enhanced Signal

Introduction Hyperpolarized (HP) [1-C]pyruvate has been shown to be metabolized to [C]bicarbonate and other products both in vivo and in isolated perfused hearts. The appearance of a [C]bicarbonate signal following an injection of hyperpolarized [1-C]pyruvate reflects the activity of pyruvate dehydrogenase (PDH) in heart. In some metabolic circumstances, the [C]bicarbonate signal is low and consequently the time-dependent evolution of this signal is difficult to characterize. Unlike traditional NMR spectroscopy, hyperpolarized substances lose magnetization with time due to two effects, application of a series of RF readout pulses to observe the signal as well as T1 relaxation. However, frequency selective RF readout pulses could be used to detect [C]bicarbonate without concomitant destruction of the “upstream” HP pyruvate signal. This in effect would conserve HP [1-C]pyruvate for a longer period of time and increase the amount of HP [C]bicarbonate detected on each scan.