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  1. Free, publicly-accessible full text available July 1, 2024
  2. null (Ed.)
    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. 
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  3. Abstract

    The feasibility of Carbon‐13 Radiofrequency (RF) Amplification by Stimulated Emission of Radiation (C‐13 RASER) is demonstrated on a bolus of liquid hyperpolarized ethyl [1‐13C]acetate. Hyperpolarized ethyl [1‐13C]acetate was prepared via pairwise addition of parahydrogen to vinyl [1‐13C]acetate and polarization transfer from nascent parahydrogen‐derived protons to the carbon‐13 nucleus via magnetic field cycling yielding C‐13 nuclear spin polarization of approximately 6 %. RASER signals were detected from samples with concentration ranging from 0.12 to 1 M concentration using a non‐cryogenic 1.4T NMR spectrometer equipped with a radio‐frequency detection coil with a quality factor (Q) of 32 without any modifications. C‐13 RASER signals were observed for several minutes on a single bolus of hyperpolarized substrate to achieve 21 mHz NMR linewidths. The feasibility of creating long‐lasting C‐13 RASER on biomolecular carriers opens a wide range of new opportunities for the rapidly expanding field of C‐13 magnetic resonance hyperpolarization.

     
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  4. Abstract

    The feasibility of Carbon‐13 Radiofrequency (RF) Amplification by Stimulated Emission of Radiation (C‐13 RASER) is demonstrated on a bolus of liquid hyperpolarized ethyl [1‐13C]acetate. Hyperpolarized ethyl [1‐13C]acetate was prepared via pairwise addition of parahydrogen to vinyl [1‐13C]acetate and polarization transfer from nascent parahydrogen‐derived protons to the carbon‐13 nucleus via magnetic field cycling yielding C‐13 nuclear spin polarization of approximately 6 %. RASER signals were detected from samples with concentration ranging from 0.12 to 1 M concentration using a non‐cryogenic 1.4T NMR spectrometer equipped with a radio‐frequency detection coil with a quality factor (Q) of 32 without any modifications. C‐13 RASER signals were observed for several minutes on a single bolus of hyperpolarized substrate to achieve 21 mHz NMR linewidths. The feasibility of creating long‐lasting C‐13 RASER on biomolecular carriers opens a wide range of new opportunities for the rapidly expanding field of C‐13 magnetic resonance hyperpolarization.

     
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  5. Abstract

    Metabolic magnetic resonance imaging (MRI) using hyperpolarized (HP) pyruvate is becoming a non‐invasive technique for diagnosing, staging, and monitoring response to treatment in cancer and other diseases. The clinically established method for producing HP pyruvate, dissolution dynamic nuclear polarization, however, is rather complex and slow. Signal Amplification By Reversible Exchange (SABRE) is an ultra‐fast and low‐cost method based on fast chemical exchange. Here, for the first time, we demonstrate not only in vivo utility, but also metabolic MRI with SABRE. We present a novel routine to produce aqueous HP [1‐13C]pyruvate‐d3for injection in 6 minutes. The injected solution was sterile, non‐toxic, pH neutral and contained ≈30 mM [1‐13C]pyruvate‐d3polarized to ≈11 % (residual 250 mM methanol and 20 μM catalyst). It was obtained by rapid solvent evaporation and metal filtering, which we detail in this manuscript. This achievement makes HP pyruvate MRI available to a wide biomedical community for fast metabolic imaging of living organisms.

     
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  6. Abstract

    Die metabolische Magnetresonanztomographie (MRT) mit hyperpolarisiertem (HP) Pyruvat wird zu einer vielversprechenden, nicht‐invasiven Technik für die Diagnose, die Charakterisierung und die Überwachung bei Behandlung von Krebs, sowie bei anderen Erkrankungen. Die klinisch etablierte Methode zur Herstellung HP‐Pyruvats, die dynamische Kernpolarisation, ist jedoch ein komplexes und langwieriges Verfahren. Die Signalverstärkung durch reversiblen Austausch (SABRE) ist eine ultraschnelle und kostengünstige Methode, die auf einem schnellen chemischen Austausch beruht. Hier demonstrieren wir zum ersten Mal eine in vivoAnwendung, sowie auch metabolische MRT mit SABRE. Wir präsentieren eine neuartige Routine zur Herstellung von wässrigem HP‐[1‐13C]Pyruvat‐d3innerhalb von sechs Minuten, zur Anwendung in lebenden Organismen. Die injizierte Lösung war steril, ungiftig, pH‐neutral und enthielt ≈30 mM [1‐13C]Pyruvat‐d3, polarisiert auf ≈11 % (Rückstände von 250 mM Methanol und 20 μM Katalysator). Es wurde durch schnelle Lösungsmittelverdampfung und Metallfiltrierung gewonnen, die wir in diesem Manuskript ausführlich beschreiben. Diese Ergebnisse machen die HP‐Pyruvat‐MRT für eine breite biomedizinische Gemeinschaft zur schnellen metabolischen Bildgebung von lebenden Organismen verfügbar.

     
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