title: Trace apparent diffusion coefficients of metabolites in human brain using diffusion weighted magnetic resonance spectroscopy.
abstract: The rotationally invariant trace/3 apparent diffusion coefficients (ADC) of N-acetyl aspartate (NAA), creatine and phosphocreatine (tCr), and choline (Cho) were determined using a diffusion-weighted stimulated echo acquisition mode sequence at 3 T in three separate human brain regions, namely the subcortical white matter, occipital gray matter, and frontal gray matter. The measurement of the mean diffusivity eliminates the dependence of the measured ADC on the direction of the diffusion gradient relative to the tissue microstructure (i.e., anisotropy). Macroscopic brain motions induce phase errors that were compensated for by phasing (zero and first order) on the single average spectrum (zero order on the NAA peak) prior to summing the individual spectra. This method yielded reproducible trace/3 ADC values in the expected range without the use of cardiac gating. The mean diffusivity of NAA (0.14 +/- 0.03 x 10(-3) mm(2)/s) appears to be less than that of tCr (0.17 +/- 0.04 x 10(-3) mm(2)/s) and Cho (0.18 +/- 0.05 x 10(-3) mm(2)/s) in human brain.
authors.affiliation: Department of Biomedical Engineering, University of Alberta, Edmonton, Canada.
authors.forename: Jacob
authors.initials: J
authors.lastname: Ellegood
authors.forename: Chris C
authors.initials: CC
authors.lastname: Hanstock
authors.forename: Christian
authors.initials: C
authors.lastname: Beaulieu
mesh_terms: D016880:Anisotropy; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001923:Brain Chemistry; D002794:Choline / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010725:Phosphocreatine / Q000378:metabolism; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted
chemical_list: D010725:Phosphocreatine; D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline