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Abstract Hyperpolarized¹³C MRI visualizes real-time metabolic processes in vivo. In this study, we achieved high¹³C polarization in situ in the bore of an MRI system for precursor molecules of most widely employed hyperpolarized agents: [1-¹³C]acetate and [1-¹³C]pyruvate ethyl esters in their perdeuterated forms, enhancing hyperpolarization lifetimes, hyperpolarized toP_13C ≈ 28% at 80 mM concentration andP_13C ≈ 19% at 10 mM concentration, respectively. Using vinyl esters as unsaturated Parahydrogen-Induced Polarization via Side-Arm Hydrogenation (PHIP-SAH) precursors and our novel polarization setup, we achieved these hyperpolarization levels by fast side-arm hydrogenation in acetone-d₆at elevated temperatures (up to 90°C) and hydrogenation pressures (up to 32 bar). We optimized the hyperpolarization process, reducing it to under 10 s, and employed advanced pulse sequences to enhance the polarization transfer efficiency. The hyperpolarization system has a small footprint, allowing it to be positioned in the same magnet, where¹³C MRI is performed. We exemplified the utility of the design with sub-second in situ¹³C MRI of ethyl [1-¹³C]pyruvate-d₆. However, challenges remain in side-arm cleavage and purification in the MRI system to extract highly polarized aqueous agent solutions. Our results showcase efficient and rapid¹³C hyperpolarization of these metabolite precursors in an MRI system with minimal additional hardware, promising to enhance future throughput and access to hyperpolarized¹³C MRI. 

The signal enhancement provided by the hyperpolarization of nuclear spins of metabolites is a promising technique for diagnostic magnetic resonance imaging (MRI). To date, most 13 C-contrast agents are hyperpolarized utilizing a complex or cost-intensive polarizer. Recently, the in situ para hydrogen-induced 13 C hyperpolarization was demonstrated. Hydrogenation, spin order transfer (SOT) by a pulsed NMR sequence, in vivo administration, and detection was achieved within the magnet bore of a 7 Tesla MRI system. So far, the hyperpolarization of the xenobiotic molecule 1- 13 C-hydroxyethylpropionate (HEP) and the biomolecule 1- 13 C-succinate (SUC) through the PH-INEPT+ sequence and a SOT scheme proposed by Goldman et al. , respectively, was shown. Here, we investigate further the hyperpolarization of SUC at 7 Tesla and study the performance of two additional SOT sequences. Moreover, we present first results of the hyperpolarization at high magnetic field of 1- 13 C-phospholactate (PLAC), a derivate to obtain the metabolite lactate, employing the PH-INEPT+ sequence. For SUC and PLAC, 13 C polarizations of about 1–2% were achieved within seconds and with minimal equipment. Effects that potentially may explain loss of 13 C polarization have been identified, i.e. low hydrogenation yield, fast T 1 / T 2 relaxation and the rarely considered 13 C isotope labeling effect.