The apparent dependence of the diffusion coefficient of N-acetylaspartate upon magnetic field strength: evidence of an interaction with NMR methodology

✍ Scribed by David N. Guilfoyle; Raymond F. Suckow; Morris H. Baslow

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 121 KB
• Volume: 16
• Category: Article
• ISSN: 0952-3480
• DOI: 10.1002/nbm.849

✦ Synopsis

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°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. Copyright © 2003 John Wiley & Sons, Ltd.