In VivoQuantitation of Cerebral Metabolite Concentrations Using Natural AbundanceC MRS at 1.5 T

A method for the quantitation of cerebral metabolites on a clinical MR scanner by natural abundance¹³C MRSin vivois described. Proton-decoupled spectra were acquired with a power deposition within FDA guidelines using a novel coil design.myo-Inositol, quantified by a separate proton MRS, and readily detectable in¹³C MRS, was used as an internal reference. Normal concentrations, measured in four control subjects, age 7 months to 12 years, were 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, glutamate was reduced to 46% of normal, 4.6 ± 0.5 mmol/kg. NAA was increased by 50% to 13.2 ± 1.6 mmol/kg in¹³C MRS, consistent with the 41% increase to 12.3 ± 1.1 from control 8.7 ± 1.1 mmol/kg assayed by¹H MRS. Limited concentration of glutamate may impact on glutamatergic neurons and excitatory neurotransmission in Canavan disease. Quantitation of cerebral glutamate in human brain may have clinical value in human neuropathologies in which glutamate is believed to play a central role.