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.