Parameterization of spectral baseline directly from short echo time full spectra in 1H-MRS

Purpose To investigate the feasibility of parameterizing macromolecule (MM) resonances directly from short echo time (TE) spectra rather than pre-acquired, T1-weighted, metabolite-nulled spectra in 1H-MRS. Methods Initial line parameters for metabolites and MMs were set for rat brain spectra acquired at 9.4 Tesla upon a priori knowledge. Then, MM line parameters were optimized over several steps with fixed metabolite line parameters. The proposed method was tested by estimating metabolite T1. The results were compared with those obtained with two existing methods. Furthermore, subject-specific, spin density-weighted, MM model spectra were generated according to the MM line parameters from the proposed method for metabolite quantification. The results were compared with those obtained with subject-specific, T1-weighted, metabolite-nulled spectra. Results The metabolite T1 were largely in close agreement among the three methods. The spin density-weighted MM resonances from the proposed method were in good agreement with the T1-weighted, metabolite-nulled spectra except for the MM resonance at ∼3.2 ppm. The metabolite concentrations estimated by incorporating these two different spectral baselines were also in good agreement except for several metabolites with resonances at ∼3.2 ppm. Conclusion The MM parameterization directly from short-TE spectra is feasible. Further development of the method may allow for better representation of spectral baseline with negligible T1-weighting. Magn Reson Med 78:836–847, 2017. © 2016 International Society for Magnetic Resonance in Medicine.