title: Comparison of NAA measures by MRS and HPLC.
abstract: This work investigates the accuracy of an in vivo estimation of absolute N-acetyl aspartate (NAA) concentrations by magnetic resonance spectroscopy (MRS) using cerebral water as an internal reference standard. Single-voxel, proton spectroscopy was carried out in two groups of rats (normal and diffuse head injury), using a PRESS sequence with TR = 3 s, TE = 135 ms. Fully relaxed water spectra and water-suppressed proton spectra were obtained from a 7 x 5 x 5 mm3 volume of tissue. MRI-based brain water content measurements were also performed. Following MRS, HPLC determinations of NAA were carried out. In the normal rats the MRS yielded 10.98 +/- 0.83 mmol/kg w.w. vs 10.76 +/- 0.76 for HPLC with a mean absolute difference of 0.8. In the injured rats the corresponding results were 9.41 +/- 1.78 (MRS) and 8.16 +/- 0.77 (HPLC) with a mean absolute difference of 1.66. The in vivo absolute method accurately documented the temporal NAA changes compared to the NAA/Cr approach.
authors.affiliation: Division of Radiation Physics, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: P P
authors.initials: PP
authors.lastname: Fatouros
authors.forename: D L
authors.initials: DL
authors.lastname: Heath
authors.forename: A
authors.initials: A
authors.lastname: Beaumont
authors.forename: F D
authors.initials: FD
authors.lastname: Corwin
authors.forename: S
authors.initials: S
authors.lastname: Signoretti
authors.forename: R H
authors.initials: RH
authors.lastname: al-Samsam
authors.forename: B
authors.initials: B
authors.lastname: Alessandri
authors.forename: P
authors.initials: P
authors.lastname: Lazzarino
authors.forename: R
authors.initials: R
authors.lastname: Vagnozzi
authors.forename: B
authors.initials: B
authors.lastname: Tavazzi
authors.forename: R
authors.initials: R
authors.lastname: Bullock
authors.forename: A
authors.initials: A
authors.lastname: Marmarou
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D001924:Brain Concussion / Q000175:diagnosis / Q000503:physiopathology*; D001929:Brain Edema / Q000175:diagnosis / Q000503:physiopathology*; D002851:Chromatography, High Pressure Liquid; D003401:Creatine / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology*; D005110:Extracellular Space / Q000502:physiology; D009682:Magnetic Resonance Spectroscopy; D011237:Predictive Value of Tests; D051381:Rats
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine