Microsoft Word - ISMRM2009-001197.DOC

Introduction Glycogen (Glyc) is the main energy store in the brain, but its precise role remains to be fully understood. To further characterize the role of brain Glyc, its metabolic characteristics and concentration need to be determined. The only in vivo method available has been based on the incorporation of 1-C-labeled glucose (Glc) into brain 1-C Glyc and its detection with localized NMR. Among the challenges of this technique is the differentiation of increases in Glyc signal due to changes in C isotopic enrichment (IE, the percentage of the molecule that contains the C isotope) from changes in total Glyc concentration. In this study we present an approach based on the “pre-labeled” C1 position of Glyc and an acute infusion of C1,6 Glc, leading to the C1 of Glyc to represent total concentration changes and the C6 position to reflect flux through the synthesis pathway. The aim therefore was to establish the localized measurement of C6 at the same time as C1 labeled Glyc. To minimize large chemical shift displacement errors due to the 39 ppm difference between the C1 and C6 resonances, a novel sequence based on the Fourier series window (FSW,1) was implemented.