Spurious signals in DQF spectroscopy: two-shot stimulated echoes.

Détails

ID Serval
serval:BIB_7BDBC00E7050
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Titre
Spurious signals in DQF spectroscopy: two-shot stimulated echoes.
Périodique
Magma
Auteur(s)
Pictet J., van der Klink J.J., Meuli R.
ISSN
0968-5243 (Print)
ISSN-L
0968-5243
Statut éditorial
Publié
Date de publication
11/2004
Volume
17
Numéro
2
Pages
74-79
Langue
anglais
Notes
Publication types: Evaluation Studies ; Journal Article ; Research Support, Non-U.S. Gov't Publication Status: ppublish
Résumé
The most widely used technique for double-quantum filtered (DQF) single-voxel spectroscopy (SVS) is based on a symmetric PRESS sequence with two additional spatially unselective pi/2 pulses, one of which is usually frequency selective. The actual filtering, rejecting signals from all uncoupled resonances, can be done by suitable phase cycling of the rf pulses in successive shots, but in practice gradient filtering is always used. Under usual conditions the sequence repetition time is comparable to the spin-lattice relaxation time, and a stimulated echo is formed by five out of the ten rf pulses in two consecutive shots. This echo is not filtered out by the gradients, and additional phase cycling is needed to eliminate it. Its spatial origin is the full transverse slice selected by the last pulse of the PRESS sequence. The SVS shimming procedure may create an important field variation in this slice (outside the volume of interest VOI). Water singlet signals therefore appear in a band of frequencies other than 4.7 ppm, and remain unaffected by water suppression pulses. In practice phase-alternation schemes can reduce these spurious signals by several orders of magnitude, but even then they may mask the weak metabolite signals of interest. We describe a strategy to minimize these spurious signals and propose a 16-step phase cycling scheme that attenuates the stimulated echo in every two-step subcycle.
Mots-clé
Algorithms, Artifacts, Magnetic Resonance Spectroscopy/methods, Signal Processing, Computer-Assisted
Pubmed
Web of science
Création de la notice
08/04/2008 14:48
Dernière modification de la notice
20/08/2019 14:37
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