High-resolution hyperpolarized in vivo metabolic ¹³C spectroscopy at low magnetic field (48.7 mT) following murine tail-vein injection

High-resolution ¹³C NMR spectroscopy of hyperpolarized succinate-1-¹³C-2,3-d₂ is reported in vitro and in vivo using a clinical-scale, biplanar (80 cm-gap) 48.7 mT permanent magnet with a high homogeneity magnetic field. Non-localized ¹³C NMR spectra were recorded at 0.52 MHz resonance frequency over the torso of a tumor-bearing mouse every 2 s. Hyperpolarized ¹³C NMR signals with linewidths of ∼3 Hz (corresponding to ∼6 ppm) were recorded in vitro (2 mL in a syringe) and in vivo (over a mouse torso). Comparison of the full width at half maximum (FWHM) for ¹³C NMR spectra acquired at 48.7 mT and at 4.7 T in a small-animal MRI scanner demonstrates a factor of ∼12 improvement for the ¹³C resonance linewidth attainable at 48.7 mT compared to that at 4.7 T in vitro. ¹³C hyperpolarized succinate-1-¹³C resonance linewidths in vivo are at least one order of magnitude narrower at 48.7 mT compared to those observed in high-field (≥3 T) studies employing HP contrast agents. The demonstrated high-resolution ¹³C in vivo spectroscopy could be useful for high-sensitivity spectroscopic studies involving monitoring HP agent uptake or detecting metabolism using HP contrast agents with sufficiently large ¹³C chemical shift differences.