Deuterated water imaging of the rat brain following metabolism of [ H ]glucose.

PURPOSE

To determine whether deuterated water (HDO) generated from the metabolism of [ H ]glucose is a sensitive biomarker of cerebral glycolysis and oxidative flux.

METHODS

A bolus of [ H ]glucose was injected through the tail vein at 1.95 g/kg into Sprague-Dawley rats. A H surface coil was placed on top of the head to record H spectra of the brain every 1.3 minutes to measure glucose uptake and metabolism to HDO, lactate, and glutamate/glutamine. A two-point Dixon method based on a gradient-echo sequence was used to reconstruct deuterated glucose and water (HDO) images selectively.

RESULTS

The background HDO signal could be detected and imaged before glucose injection. The H NMR spectra showed arrival of [ H ]glucose and its metabolism in a time-dependent manner. A ratio of the HDO to glutamate/glutamine resonances demonstrates a pseudo-steady state following injection, in which cerebral metabolism dominates wash-in of HDO generated by peripheral metabolism. Brain spectroscopy reveals that HDO generation is linear with lactate and glutamate/glutamine appearance in the appropriate pseudo-steady state window. Selective imaging of HDO and glucose is easily accomplished using a gradient-echo method.

CONCLUSION

Metabolic imaging of HDO, as a marker of glucose, lactate, and glutamate/glutamine metabolism, has been shown here for the first time. Cerebral glucose metabolism can be assessed efficiently using a standard gradient-echo sequence that provides superior in-plane resolution compared with CSI-based techniques.