Discrimination between neurochemical and macromolecular signals in human frontal lobes using short echo time proton magnetic resonance spectroscopy.
Magnetic resonance spectra from large (35 cm3) frontal lobe voxels in vivo were analyzed using LCModel, with and without subtraction of a "metabolite nulled" spectrum with an inversion time of 650 ms to characterize the macromolecule baseline. Baseline subtraction decreased the signal to noise ratio (SNR), but improved the reliability of LCModel quantification of most metabolites, as reflected in the Cramer-Rao lower bounds, in particular for glutamate and glutamine. The reported concentrations increased for glutamine, creatine, and lactate, and decreased for glutamate, myo-inositol and NAAG, but the sum of all metabolites remained constant, as did the standard deviation of the concentrations in the control group. Macromolecule subtraction is worthwhile when SNR is high, as in the characterization of normal-appearing tissue in the brain.
McLean
Mary A
MA
MRI Unit, National Society for Epilepsy, Chalfont St. Peter, Gerrard's Cross, Bucks, UK SL9 0RJ.
Simister
Robert J
RJ
Barker
Gareth J
GJ
Duncan
John S
JS
D000465:Algorithms; D001923:Brain Chemistry / Q000502:physiology*; D005625:Frontal Lobe / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy
D046911:Macromolecular Substances