title: The apparent dependence of the diffusion coefficient of N-acetylaspartate upon magnetic field strength: evidence of an interaction with NMR methodology.
abstract: An inverse relationship between applied magnetic field strength and the apparent diffusion coefficient (ADC) of several important brain metabolites including N-acetyl-l-aspartate (NAA), choline and creatine, measured in vivo using proton magnetic resonance spectroscopy (MRS), has been reported. In this investigation, using phantom studies of NAA at magnetic field strengths of 3 and 7 T, these observations have been verified under controlled MRS conditions in vitro, and the ADC of NAA has been found to vary inversely with magnetic field strength, decreasing at a rate of 2.5%/T at 20 degrees C. We have also assessed whether the effect is a function of a systemic bias in methodology, or if the effect is actually on the rate of molecular diffusion. This was done using an MRS-independent method for measurement of molecular diffusion in NAA phantoms at 0, 0.025 and 7 T applied magnetic field strengths. As a result, it has been demonstrated that the observed apparent magnetic field dependence of the ADC of NAA is a consequence of the NMR measurement and is apparently not a real effect on molecular diffusion.
authors.affiliation: Nathan S. Kline Institute for Psychiatric Research, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA. Guilfoyl@nki.rfmh.org
authors.forename: David N
authors.initials: DN
authors.lastname: Guilfoyle
authors.forename: Raymond F
authors.initials: RF
authors.lastname: Suckow
authors.forename: Morris H
authors.initials: MH
authors.lastname: Baslow
mesh_terms: D016477:Artifacts; D001216:Asparagine / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism* / Q000528:radiation effects*; D015415:Biomarkers / Q000032:analysis*; D001921:Brain / Q000378:metabolism*; D001931:Brain Mapping / Q000379:methods*; D004058:Diffusion; D004307:Dose-Response Relationship, Radiation; D004574:Electromagnetic Fields; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; D001216:Asparagine; C026988:N-acetylasparagine