Purpose
The objective of the present work was to develop and implement an efficient approach to hyperpolarize [1‐13C]acetate and apply it to in vivo cardiac spectroscopy and imaging.
Methods
Rapid hydrogen peroxide induced decarboxylation was used to convert hyperpolarized [2‐13C]pyruvate into highly polarized [1‐13C]acetate employing an additional step following rapid dissolution of [2‐13C]pyruvate in a home‐built multi‐sample dissolution dynamic nuclear polarization system. Phantom dissolution experiments were conducted to determine optimal parameters of the decarboxylation reaction, retaining polarization and T1 of [1‐13C]acetate. In vivo feasibility of detecting [1‐13C]acetate metabolism is demonstrated using slice‐selective spectroscopy and multi‐echo imaging of [1‐13C]acetate and [1‐13C]acetylcarnitine in the healthy rat heart.
Results
The first in vivo signal was observed ~23 s after dissolution. At the corresponding time point in the phantom experiments, 97.9 ± 0.4% of [2‐13C]pyruvate were converted into [1‐13C]acetate by the decarboxylation reaction. T1 and polarization of [1‐13C]acetate was determined to be 29.7 ± 1.9% and a 47.7 ± 0.5 s. Polarization levels of [2‐13C]pyruvate and [1‐13C]acetate were not significantly different after transfer to the scanner. In vivo, [1‐13C]acetate and [1‐13C]acetylcarnitine could be detected using spectroscopy and imaging.
Conclusion
Decarboxylation of hyperpolarized [2‐13C]pyruvate enables the efficient production of highly polarized [1‐13C]acetate that is applicable to study short‐chain fatty acid metabolism in the in vivo heart.