FIG. 8.

POCE MRS can be used to enhance the detection of ¹³C-enriched metabolites. A: Standard ¹H acquisition. B: The incorporation of an additional ¹³C pulse in the ¹H pulse sequence selectively inverts the signal of all ¹H bound to ¹³C; ¹H bound to ¹²C are unaffected. C: The difference spectrum (A minus B) yields only ¹³C-enriched metabolites. Fractional enrichment can be calculated from the ratio of C-to-A. These example spectra from a muscle extract show ¹³C enrichment at multiple sites, including the C₄ and C₃ positions of glutamate (Glu) and glutamine (Gln) and C₃-alanine (Ala).