Application of LCModel for quality control and quantitative in vivo1H MR spectroscopy by short echo time STEAM sequence

The linear combination of model spectra (LCModel) calculation of a parameter for long-term quality control,k _T, was introduced, representing the ratio of the temporal and nominal intensities of CH₃ groups of lactate and acetate in a quality control phantom. This procedure is a part of the quality assurance of the scanner using fully automatic measurement and calculation ofk _T parameters, and utilizing Shewhart regulation control charts for continuous evaluation of the magnetic resonance (MR) scanner setting. The application of thek _T parameter for the correction of in vivo data increases the precision of molar concentration determination by about 4%. This was tested by the quantitative in vivo MR determination of the molar concentrations of 13 prominent metabolites (N-acetylaspartate (NAA),N-acetylaspartylgutamate, creatine and phosphocreatine (Cr), choline-containing compounds (Cho), myo-inositol, scyllo-inositol., γ-aminobutyric acid, glutamine, glutamate, glucose, lactate, alanine, taurine) in the white matter and hippocampus of the brain in groups of volunteers, using a short echo time stimulated echo acquisition mode sequence (echo time =10 ms) and the LCModel technique. The repeatability of the measurement of prominent metabolites such as NAA, Cr and Cho was found to be around 10% (relative standard deviation,n=6); precision in a group of volunteers (n=20 and 28, respectively) was in the range of approximately 13–20%. For other metabolites, which are measured with a lower signal-to-noise ratio, the precision can be much lower.