title: In vivo quantification of brain metabolites by 1H-MRS using water as an internal standard.
abstract: The reliability of absolute quantification of average metabolite concentrations in the human brain in vivo by 1H-MRS using the fully relaxed water signal as an internal standard was tested in a number of in vitro as well as in vivo measurements. The experiments were carried out on a SIEMENS HELICON SP 63/84 wholebody MR-scanner operating at 1.5 T using a STEAM sequence. In vitro studies indicate a very high correlation between metabolite signals (area under peaks) and concentration, R = 0.99 as well as between metabolite signals and the volume of the selected voxel, R = 1.00. The error in quantification of N-acetyl aspartate (NAA) concentration was about 1-2 mM (6-12%). Also in vivo a good linearity between water signal and selected voxel size was seen. The same was true for the studied metabolites, N-acetyl aspartate (NAA), creatine/phosphocreatine (Cr/PCr), and choline (Cho). Calculated average concentrations of NAA, Cr/PCr, and Cho in the occipital lobe of the brain in five healthy volunteers were (mean +/- 1 SD) 11.6 +/- 1.3 mM, 7.6 +/- 1.4 mM, and 1.7 +/- 0.5 mM. The results indicate that the method presented offers reasonable estimation of metabolite concentrations in the brain in vivo and therefore is useful in clinical research.
authors.affiliation: Danish Research Center of Magnetic Resonance, Hvidovre Hospital, University of Copenhagen, Denmark.
authors.forename: P
authors.initials: P
authors.lastname: Christiansen
authors.forename: O
authors.initials: O
authors.lastname: Henriksen
authors.forename: M
authors.initials: M
authors.lastname: Stubgaard
authors.forename: P
authors.initials: P
authors.lastname: Gideon
authors.forename: H B
authors.initials: HB
authors.lastname: Larsson
mesh_terms: D001834:Body Water / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D005069:Evaluation Studies as Topic; D006801:Humans; D006859:Hydrogen; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D008433:Mathematics; D008961:Models, Structural; D012016:Reference Values; D013997:Time Factors
chemical_list: D006859:Hydrogen