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MRS of pilocytic astrocytoma: The peak at 2 ppm may not be NAA
Author(s) -
Tamrazi Benita,
Nelson Marvin D.,
Blüml Stefan
Publication year - 2017
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26374
Subject(s) - pilocytic astrocytoma , nuclear magnetic resonance , astrocytoma , nuclear medicine , chemistry , creatine , chemical shift , in vivo magnetic resonance spectroscopy , magnetic resonance imaging , medicine , glioma , radiology , physics , cancer research , biochemistry
Purpose To determine whether the chemical shift of residual N‐acetylaspartate (NAA) signal in pilocytic astrocytomas (PA) is consistent with the position of the NAA peak in controls. Methods MR spectra from 27 pediatric World Health Organization (WHO) grade I pilocytic astrocytoma patients, fifteen patients with WHO grade II and high‐grade (III–IV) astrocytomas, and 36 controls were analyzed. All spectra were acquired with a short echo time (35 ms), single voxel point‐resolved spectroscopy sequence on clinical 3 tesla scanners. Fully automated LCModel software was used for processing, which included the fitting of peak positions for NAA and creatine (Cr). Results The chemical shift difference between the NAA and Cr peaks was significantly smaller (by 0.016 ± 0.005 parts per million, P < 1e–10) in PAs than in controls and was also smaller than what was observed in infiltrative astrocytomas. Conclusion The chemical shift position of the residual NAA peak in PAs is not consistent with NAA. The signal likely originates from an N‐acetyl group of one or more other chemicals such as N‐acetylated sugars. Magn Reson Med 78:452–456, 2017. © 2016 International Society for Magnetic Resonance in Medicine