Deuterium metabolic imaging of the human brain in vivo at 7 T

Purpose: To explore the potential of deuterium metabolic imaging (DMI) in the human brain in vivo at 7 T, using a multi-element deuterium (²H) RF coil for 3D volume coverage. Methods: ¹H-MR images and localized ²H MR spectra were acquired in vivo in the human brain of 3 healthy subjects to generate DMI maps of ²H-labeled water, glucose, and glutamate/glutamine (Glx). In addition, non-localized ²H-MR spectra were acquired both in vivo and in vitro to determine T₁ and T₂ relaxation times of deuterated metabolites at 7 T. The performance of the ²H coil was assessed through numeric simulations and experimentally acquired B₁⁺ maps. Results: 3D DMI maps covering the entire human brain in vivo were obtained from well-resolved deuterated (²H) metabolite resonances of water, glucose, and Glx. The T₁ and T₂ relaxation times were consistent with those reported at adjacent field strengths. Experimental B₁⁺ maps were in good agreement with simulations, indicating efficient and homogeneous B₁⁺ transmission and low RF power deposition for ²H, consistent with a similar array coil design reported at 9.4 T. Conclusion: Here, we have demonstrated the successful implementation of 3D DMI in the human brain in vivo at 7 T. The spatial and temporal nominal resolutions achieved at 7 T (i.e., 2.7 mL in 28 min, respectively) were close to those achieved at 9.4 T and greatly outperformed DMI at lower magnetic fields. DMI at 7 T and beyond has clear potential in applications dealing with small brain lesions.