Exchange‐linked dissolution agents in dissolution‐DNP 13C metabolic imaging

Abstract

The use of unlabeled exchange-linked dissolution agents in hyperpolarized metabolic imaging was studied to examine pool size limits and saturation relative to the availability of NADH. Three-dimensional dynamic metabolic images were obtained, and compared following injection of a bolus of hyperpolarized [1-(13)C]pyruvate, prepared with and without unlabeled sodium lactate in the dissolution buffer. Comparisons were made on the basis of apparent rate constants and [1-(13)C]lactate signal-to-noise ratio. Range finding data were obtained for different bolus compositions. Isotope exchange was also probed in the reverse direction, following injection of a bolus of hyperpolarized [1-(13)C]lactate, with and without unlabeled sodium pyruvate in the dissolution buffer. Liver, kidney, and vascular regions of interest all showed an increase in [1-(13)C]lactate signal with addition of unlabeled sodium lactate in the dissolution buffer. Injection of hyperpolarized [1-(13)C]lactate with unlabeled sodium pyruvate in the dissolution buffer, provided exchange rate constants Klp for kidney and vascular regions of interest. These results are consistent with a high level of (13)C-exchange, and with labeling rates that are limited by steady-state pool sizes in vivo.