In vivo detection of brain glycine with echo‐time‐averaged 1 H magnetic resonance spectroscopy at 4.0 T

A single‐voxel proton magnetic resonance spectroscopy ( 1 H‐MRS) method is described that enables the in vivo measurement of endogenous brain glycine (Gly) levels in human subjects. At 4.0 T, TE‐averaging 1 H‐MRS dramatically attenuates the overlapping myo ‐inositol (mI) resonances at 3.52 ppm, permitting a more reliable measure of the Gly singlet peak. This methodology initially is described and tested in phantoms. The phantom data infers that the 3.55‐ppm peak predominantly is Gly with a smaller contribution from mI. The composite resonance thus is differentiated from pure Gly and mI and is labeled Gly*. The mI contribution was calculated as <2% of the total Gly* signal for a 1:1 mI/Gly mixture. The technique subsequently was used to acquire TE‐averaged 1 H‐MRS data from the occipital cortex of healthy control subjects. The resultant spectra closely resembled experimental phantom data. LC‐model analysis provided a means for quantifying TE‐averaged 1 H‐MRS spectra and a mean test–retest variability measure of 15% was established for brain Gly* levels in studies of six healthy subjects. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.