Production of highly polarized [1-13C]acetate by rapid decarboxylation of [2-13C]pyruvate - application to hyperpolarized cardiac spectroscopy and imaging

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