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.
Prescot
Andrew P
AP
Brain Imaging Center, McLean Hospital, Belmont, Massachusetts 02478, USA. aprescot@mclean.harvard.edu
de B Frederick
Blaise
B
Wang
Liqun
L
Brown
John
J
Jensen
J Eric
JE
Kaufman
Marc J
MJ
Renshaw
Perry F
PF
D000328:Adult; D001923:Brain Chemistry; D005260:Female; D005998:Glycine / Q000032:analysis*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male
D005998:Glycine