A comparison of in vivo 13 C MR brain glycogen quantification at 9.4 and 14.1 T

The high molecular weight and low concentration of brain glycogen render its noninvasive quantification challenging. Therefore, the precision increase of the quantification by localized 13 C MR at 9.4 to 14.1 T was investigated. Signal‐to‐noise ratio increased by 66%, slightly offset by a T 1 increase of 332 ± 15 to 521 ± 34 ms. Isotopic enrichment after long‐term 13 C administration was comparable (∼40%) as was the nominal linewidth of glycogen C1 (∼50 Hz). Among the factors that contributed to the 66% observed increase in signal‐to‐noise ratio, the T 1 relaxation time impacted the effective signal‐to‐noise ratio by only 10% at a repetition time = 1 s. The signal‐to‐noise ratio increase together with the larger spectral dispersion at 14.1 T resulted in a better defined baseline, which allowed for more accurate fitting. Quantified glycogen concentrations were 5.8 ± 0.9 mM at 9.4 T and 6.0 ± 0.4 mM at 14.1 T; the decreased standard deviation demonstrates the compounded effect of increased magnetization and improved baseline on the precision of glycogen quantification. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.