title: Global average gray and white matter N-acetylaspartate concentration in the human brain.
abstract: Since the amino acid derivative N-acetylaspartate (NAA) is almost exclusive to neuronal cells in the adult mammalian brain and its concentration has shown local (or global) abnormalities in most focal (or diffuse) neurological diseases, it is considered a specific neuronal marker. Yet despite its biological and clinical prominence, the relative NAA concentration in the gray and white matter (GM, WM) remains controversial, with each reported to be higher than, equal to, or less than the other. To help resolve the controversy and importantly, access the NAA in both compartments in their entirety, we introduce a new approach to distinguish and quantify the whole-brain average GM and WM NAA concentration by integrating MR-image segmentation, localized and non-localized quantitative (1)H-MRS. We demonstrate and validate the method in ten healthy volunteers (5 women) 27+/-6 years old (mean+/-standard-deviation) at 1.5T. The results show that the healthy adult human brain comprises significantly less WM, 39+/-3%, than GM 60+/-4% by volume (p<0.01). Furthermore, the average NAA concentration in the WM, 9.5+/-1.0 mM, is significantly lower than in GM, 14.3+/-1.1 mM (p<0.01).
authors.affiliation: Department of Radiology, New York University School of Medicine, 650 First Avenue, 6th Floor, New York, NY 10016, USA.
authors.forename: Matilde
authors.initials: M
authors.lastname: Inglese
authors.forename: Henry
authors.initials: H
authors.lastname: Rusinek
authors.forename: Ilena C
authors.initials: IC
authors.lastname: George
authors.forename: James S
authors.initials: JS
authors.lastname: Babb
authors.forename: Robert I
authors.initials: RI
authors.lastname: Grossman
authors.forename: Oded
authors.initials: O
authors.lastname: Gonen
mesh_terms: D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000032:analysis; D001921:Brain / Q000033:anatomy & histology; D001923:Brain Chemistry; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate