In vivo H-1 MR spectra analysis by means of second derivative method

Short echo time (TE) in vivo PRESS H-1 MR spectra (2 T, TE = 35 ms) of norm al brain were fitted in the frequency domain using the second derivative me thod. In this approach, local maxima and hidden peaks are found as local mi nima of spectrum second derivative. The Lorentzian robust minimisation proc edure (referred to as maximum likelihood or m-estimate fitting) using Leven burg-Marquardt non-linear fitting engine was applied. Spectral lines were a pproximated under the assumption of the mixed Lorentzian/Gaussian lineshape s. The same procedure was applied to 18 proton spectra. The number of peaks found within the range of 0.74/4.2 parts per million (ppm) was 52 +/- 3 an d their positions were almost the same. The fitted lines were assigned on t he basis of the J-pattern recalculated for the field strength of 2 T and by comparing the chemical shifts with the shifts in the single compound spect ra. The ratios of main metabolites, such as NAA/Cr, Cho/Cr, Cho/NAA and mI/ Cr, are in accord with those obtained earlier using the software supplied w ith the MR imager and the absolute concentrations of N-acetylaspartate (NAA ), choline containing compounds (Cho), myoInositol (mI), glucose (Glc) and glutamate (Glu) obtained from the fit agree with those reported in literatu re, which confirms the usefulness of the second derivative method in routin e analyses of H-1 MR brain spectra. (C) 2001 Elsevier Science B.V. All righ ts reserved.