In vivo1H MR spectra analysis by means of second derivative method |
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Authors: | Maria Sokól |
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Affiliation: | (1) Department of Medical Physics, Maria Sklodowska-Curie Institute of Oncology, Wybrzeze Armii Krajowej 15 Str, 44 100 Gliwicc, Poland |
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Abstract: | Short echo time (TE) in vivo PRESS1H MR spectra (2 T. TE = 35 ms) of normal brain were fitted in the frequency domain using the second derivative method. In
this approach, local maxima and hidden peaks are found as local minima of spectrum second derivative. The Lorentzian robust
minimisation procedure (referred to as maximum likelihood or m-estimate fitting) using Levenburg -Marquardt non-linear fitting
engine was applied. Spectral lines were approximated under the assumption of the mixed Lorentzian/Gaussian lineshapes. 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 and their positions were almost the same. The fitted lines were assigned on the 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 spectra. The ratios
of main metabolites, such as NAA/Cr, Cho/Cr, Cho/NAA and ml/Cr, are in accord with those obtained earlier using the software
supplied with the MR imager and the absolute concentrations ofN-acetylaspartate (NAA). choline containing compounds (Cho),myo Inositol (ml), glucose (Gle) and glutamate (Glu) obtained from the fit agree with those reported in literature, which confirms
the usefulness of the second derivative method in routine analyses of1H MR brain spectra. |
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Keywords: | Brain In vivo1H MRS Spectra fitting Second derivative method Metabolite concentrations |
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