Detecting natural abundance carbon signal of NAA metabolite within 12- cm³ localized volume of human brain using ¹H-{¹³C} NMR spectroscopy

NMR spectroscopy has been applied extensively to study metabolism noninvasively in the human brain and other tissues. However, it usually suffers from poor signal-to-noise ratio due to low NMR sensitivity and low metabolite concentrations. In this study, the technique of proton-observe- carbon-edited (POCE) NMR spectroscopy combined with a single-shot localization sequence was used to detect the natural abundance carbon signal of the amino acid N-acetyl aspartate from a 12-cm³ localized volume in the occipital lobe of humans at 4 T. The results suggest that NMR spectroscopy is sensitive enough to detect signals from low concentration metabolites (<60 nmol/g) from small volumes in the human brain within several minutes of data acquisition. This reveals that in vivo NMR spectroscopy is a promising technique for detecting small metabolite changes and low traces of ¹³C isotopic labeling for dynamic metabolism studies aimed at investigating physiological and pathological questions.