Noninvasive quantification of human brain ascorbate concentration using 1H NMR spectroscopy at 7 T

Ascorbate (Asc, vitamin C) was quantified in the human brain noninvasively using two different 1H NMR spectroscopy methods: short‐echo time STEAM and MEGA‐PRESS homonuclear editing. Taking advantage of increased sensitivity and chemical shift dispersion at 7 T, Asc was quantified with increased reliability relative to our previous study accomplished at 4 T. Asc concentration quantified from short‐echo time spectra measured from the occipital lobe of eight healthy subjects ([Asc] = 1.1 ± 0.3 µmol/g, mean ± SD) was in excellent agreement with Asc concentration quantified from the same volume of interest using homonuclear editing ([Asc] = 1.2 ± 0.2 µmol/g). This agreement indicates that at 7 T, Asc can be reliably quantified in the human brain simultaneously with 15 other metabolites. Additional advantages of the short‐echo time approach were: shorter measurement time than homonuclear editing and minimal effect of T2 relaxation on Asc quantification. High magnetic field was also beneficial for Asc quantification with MEGA‐PRESS because increased chemical shift dispersion enabled editing with full efficiency, which resulted in a supra‐linear gain in signal‐to‐noise ratio relative to 4 T. Copyright © 2009 John Wiley & Sons, Ltd.