In vivo quantitation of cerebral metabolite concentrations using natural abundance C-13 MRS at 1.5 T

A method for the quantitation of cerebral metabolites on a clinical MR scan ner by natural abundance C-13 MRS in vivo is described. Proton-decoupled sp ectra were acquired with a power deposition within FDA guidelines using a n ovel coil design, myo-Inositol, quantified by a separate proton MRS, and re adily detectable in C-13 MRS, was used as an internal reference. Normal con centrations, measured in four control subjects, age 7 months to 12 years, w ere glutamate 9.9 +/- 0.7, glutamine 5.6 +/- 1.0, and NAA 8.8 +/- 2.8 mmol/ kg. In a patient diagnosed with Canavan disease, examined four times, gluta mate was reduced to 46% of normal, 4.6 +/- 0.5 mmol/kg, NAA was increased b y 50% to 13.2 +/- 1.6 mmol/kg in C-13 MRS, consistent with the 41% increase to 12.3 +/- 1.1 from control 8.7 +/- 1.1 mmol/kg assayed by H-1 MRS. Limit ed concentration of glutamate may impact on glutamatergic neurons and excit atory neurotransmission in Canavan disease. Quantitation of cerebral glutam ate in human brain may have clinical value in human neuropathologies in whi ch glutamate is believed to play a central role. (C) 1999 Academic Press.