GABA, glutamate and excitatory-inhibitory ratios measured using short-TE STEAM MRS at 7-Tesla: Effects of macromolecule basis sets and baseline parameters

Rationale and objectivesMacromolecules (MMs) affect the precision accuracy of neurochemical quantification in magnetic resonance spectroscopy. A measured MM basis is increasingly used LCModel analysis combined with a spline baseline, whose stiffness controlled by parameter named DKNTMN. The effects DKNTMN were investigated.Materials methodsTwenty-six healthy subjects prospectively enrolled scanned twice using short echo-time Stimulated Echo Acquisition Mode (STEAM) at 7-T. Using LCModel, analyses conducted simulated (MMsim) 0.15 an inhouse (MMmeas) 0.15, 0.30, 0.60 1.00. Cramér-Rao lower bound (CRLB) concentrations gamma-aminobutyric acid (GABA), glutamate excitatory-inhibitory ratio (EIR), addition to MMs statistically analyzed. Measurement stability was evaluated coefficient variation (CV).ResultsCRLBs GABA significantly when MMsim than MMmeas; levels 2–3. higher MMmeas where or 0.30 Difference concentration not significant. EIRs showed same difference as depending on values. CVs between test-retest scans relatively stable for but became larger increased EIR.ConclusionNeurochemical depends parameters sets fitting. Analysis conformed best previous studies recommended.