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Simplified 13C metabolic modeling for simplified measurements of cerebral TCA cycle rate in vivo

13C NMR spectroscopy is a unique tool to measure the cerebral tricarboxylic acid (TCA) cycle rate in vivo. The measurement relies on metabolic modeling of glutamate C3 and C4 enrichment time courses during a 13C‐glucose intravenous infusion. Usual metabolic models require the plasma glucose and 13C‐glucose time courses as input functions, as well as the knowledge of Michaelis‐Menten kinetics parameters governing passage through the blood‐brain barrier. It is shown in the present work that, when using an infusion protocol yielding a rapidly stable plasma glucose fractional enrichment, metabolic modeling can be simplified in such a manner that this additional information on input function and glucose transport is no longer required, significantly simplifying the measurement of cerebral TCA cycle rate in vivo. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.