Quantification of Brain Metabolites via LCModel

Data were analyzed as described previously²⁸ . Following a 1-Hz apodization, spectra were fitted with LCModel software^{19 (link)}, using calculated spectra of 20 metabolites as basis functions. The basis set included spectra of 2HG, NAA, GABA, glutamate, glycine, creatine, myo-inositol, glutamine, lactate, alanine, acetate, aspartate, ethanolamine, glutathione, phosphorylethanolamine, scyllo-inositol, taurine, N-acetylaspartylglutamate, glucose, and choline. The metabolite concentrations were estimated with respect to the short echo time water signal. Assuming an equal composition of gray and white matter in tumors, we used a water concentration value of 42.3 M, calculated from the literature values^{23 (link)} for the water concentrations in gray and white matter. Relaxation effects on metabolite signals were corrected using published metabolite T₂ and T₁; T₂ = 150, 230 and 280 for Cr, Cho and NAA, and 180 ms for other metabolites, respectively, and T₁ = 1.2 for 2HG, glutamate, glutamine and myo-inositol, and 1.5 for other metabolites^{20 (link)–22} .