Effect of Water Suppression and Metabolite Cycling on Quantification of ¹H MRS Spectra in the Human Brain at 3 Tesla

Purpose: This study investigates the effect of VAPOR water suppression and metabolite cycling on metabolite quantification and macromolecules in proton magnetic resonance spectroscopy. Methods: Single-voxel semi-LASER spectra (T_R/T_E = 3000/28 ms) and metabolite-nulled spectra (macromolecules) were acquired in five healthy subjects in the posterior cingulate cortex at 3 T using two different water suppression schemes: VAPOR or metabolite cycling (MC). Post-processed spectra were quantified using LCModel. Metabolites concentrations were compared between the two schemes. Results: Region specific differences in macromolecule resonances were observed and the concentration of most metabolites was significantly higher when using MC compared to VAPOR. The difference was most pronounced for total creatine (−14% with VAPOR vs. MC, p < 0.05). Conclusion: The macromolecules spectrum included in the LCModel basis set must be measured with the same water suppression scheme as the metabolite spectrum for accurate quantification.