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Contamination of single‐voxel multiple quantum filters by external water signals arising from intermolecular multiple quantum coherences
Author(s) -
Thompson Richard B.,
Allen Peter S.
Publication year - 2009
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.22061
Subject(s) - voxel , filter (signal processing) , intermolecular force , excited state , imaging phantom , quantum , signal (programming language) , nuclear magnetic resonance , physics , chemistry , biological system , optics , atomic physics , quantum mechanics , computer science , molecule , artificial intelligence , computer vision , biology , programming language
Multiple‐quantum filtered pulse sequences simplify overlapping metabolite spectra by the elimination of peaks from uncoupled spin species, most notably from methyl groups and water, and the minimization of unwanted coupled‐spin peaks. However, it is shown in this study that a significant contaminant water signal can pass through this family of filters in the form of intermolecular multiple‐quantum coherences. An imaging evaluation of a single‐voxel multiple quantum filter experiment confirms that the water contamination is excited from outside of the voxel of interest, thus having an increased potential for broad spectral contamination. Phantom and in vivo experiments at 3.0 T are used to illustrate, first, significant water contamination of a single‐voxel double quantum filter experiment optimized for the observation of glutamate, and second, the elimination of the unwanted water signal with conventional phase cycling and optimized filter gradient orientations. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.