Deuterium metabolic imaging (DMI) is a novel MR-based method to spatially map metabolism of deuterated substrates such as [6,6'-2 H 2 ]-glucose in vivo. Compared with traditional 13 C-MR-based metabolic studies, the MR sensitivity of DMI is high due to the larger 2 H magnetic moment and favorable T 1 and T 2 relaxation times.Here, the magnetic field dependence of DMI sensitivity and transmit efficiency is studied on phantoms and rat brain postmortem at 4, 9.4 and 11.7 T. The sensitivity and spectral resolution on human brain in vivo are investigated at 4 and 7 T before and after an oral dose of [6,6'-2 H 2 ]-glucose. For small animal surface coils (Ø 30 mm), the experimentally measured sensitivity and transmit efficiency scale with the magnetic field to a power of +1.75 and −0.30, respectively. These are in excellent agreement with theoretical predictions made from the principle of reciprocity for a coil noise-dominant regime. For larger human surface coils (Ø 80 mm), the sensitivity scales as a +1.65 power. The spectral resolution increases linearly due to nearconstant linewidths. With optimal multireceiver arrays the acquisition of DMI at a nominal 1 mL spatial resolution is feasible at 7 T. K E Y W O R D Sdeuterium metabolic imaging, magnetic field dependence, resolution, sensitivity | INTRODUCTIONDeuterium metabolic imaging (DMI) is a novel MR-based method to spatially map metabolism. 1 DMI lies in the category of stable isotope methods, in which an enriched substrate isotope is followed over time as it appears in downstream metabolic products. Common stable isotope methods include 13 C MR spectroscopy (MRS), 2 inverse 1 H-[ 13 C] MRS 3 and hyperpolarized 13 C MRS. 4,5 DMI is characterized by its technical simplicity and robustness as well as the relatively high sensitivity due to the larger magnetic moment and short T 1 relaxation time constants. The low natural abundance of 2 H of 0.0115% 6 leads to low-intensity water and lipid signals, thus eliminating the need for water and lipid suppression. To maximize sensitivity, the 2 H signal is excited by a single RF pulse, after which spatial localization is achieved with short 3D phase-encoding blips before FID acquisition. The robustness of DMI is further enhanced by the low sensitivity to magnetic field inhomogeneity due to the low 2 H Larmor frequency.

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Background Preclinical neuroimaging allows for the assessment of brain anatomy, connectivity and function in laboratory animals, such as mice and rats. Most of these studies are performed under anesthesia to avoid movement during the scanning sessions. Method Due to the limitations associated with anesthetized imaging, recent efforts have been made to conduct rodent imaging studies in awake animals, habituated to the restraint systems used in these instances. As of now, only one such system is commercially available for mouse scanning (Animal Imaging Research, Boston, MA, USA) integrating the radiofrequency coil electronics with the restraining element, an approach which, although effective in reducing head motion during awake imaging, has some limitations. In the current report, we present a novel mouse restraining system that addresses some of these limitations. Results/Comparison to other methods The effectiveness of the restraining system was evaluated in terms of three-dimensional linear head movement across two consecutive functional MRI scans (total 20 min) in 33 awake mice. Head movement was minimal, recorded in roughly 12% of the time-series. Respiration rate during the acclimation procedure dropped while the bolus count remained unchanged. Body movement during functional acquisitions did not have a significant effect on magnetic field (B0) homogeneity. Conclusion/novelty Compared to the commercially available system, the benefit of the current design is two-fold: 1) it is compatible with a range of commercially-available coils, and 2) it allows for the pairing of neuroimaging with other established techniques involving intracranial cannulation (i.e. microinfusion and optogenetics).