IntroductionThere is a lack of robust metabolic imaging techniques that can be routinely applied to characterize lesions in patients with brain tumors. Here we explore in an animal model of glioblastoma the feasibility to detect uptake and metabolism of deuterated choline and describe the tumor-to-brain image contrast.MethodsRG2 cells were incubated with choline and the level of intracellular choline and its metabolites measured in cell extracts using high resolution1H NMR. In rats with orthotopically implanted RG2 tumors deuterium metabolic imaging (DMI) was appliedin vivoduring, as well as 1 day after, intravenous infusion of2H9-choline. In parallel experiments, RG2-bearing rats were infused with [1,1′,2,2′-2H4]-choline and tissue metabolite extracts analyzed with high resolution2H NMR to identify molecule-specific2H-labeling in choline and its metabolites.ResultsIn vitroexperiments indicated high uptake and fast phosphorylation of exogenous choline in RG2 cells.In vivoDMI studies revealed a high signal from the2H-labeled pool of choline + metabolites (total choline,2H-tCho) in the tumor lesion but not in normal brain. Quantitative DMI-based metabolic maps of2H-tCho showed high tumor-to-brain image contrast in maps acquired both during, and 24 h after deuterated choline infusion. High resolution2H NMR revealed that DMI data acquired during2H-choline infusion consists of free choline and phosphocholine, while the data acquired 24 h later represent phosphocholine and glycerophosphocholine.DiscussionUptake and metabolism of exogenous choline was high in RG2 tumors compared to normal brain, resulting in high tumor-to-brain image contrast on DMI-based metabolic maps. By varying the timing of DMI data acquisition relative to the start of the deuterated choline infusion, the metabolic maps can be weighted toward detection of choline uptake or choline metabolism. These proof-of-principle experiments highlight the potential of using deuterated choline combined with DMI to metabolically characterize brain tumors.