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J ‐difference editing of gamma‐aminobutyric acid (GABA): Simulated and experimental multiplet patterns
Author(s) -
Near Jamie,
Evans C. John,
Puts Nicolaas A. J.,
Barker Peter B.,
Edden Richard A. E.
Publication year - 2013
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.24572
Subject(s) - multiplet , subtraction , pulse (music) , flip angle , pulse sequence , physics , coupling (piping) , nuclear magnetic resonance , chemistry , molecular physics , optics , atomic physics , materials science , mathematics , quantum mechanics , spectral line , medicine , arithmetic , detector , magnetic resonance imaging , metallurgy , radiology
Purpose : To investigate factors that influence the multiplet pattern observed in J ‐difference editing of gamma‐aminobutyric acid (GABA). Methods : Density matrix simulations were applied to investigate the shape of the 3 ppm GABA multiplet as a function of the editing sequence's slice‐selective refocusing pulse properties, in particular bandwidth, transition width, and flip angle. For comparison to the calculations, experimental measurements were also made at 3 T on a 10 mM GABA solution using the MEGA‐PRESS sequence at various refocusing pulse flip angles. Results : Good agreement was found between experiments and simulations. The edited multiplet consists of two outer lines of slightly unequal intensity due to strong coupling, and a smaller central line, the result of the unequal J ‐couplings between the C4 and C3 protons. The size of the center peak increases with increasing slice‐selective refocusing pulse transition width, and deviation of the flip angle from 180°. Conclusion : The 3 ppm GABA multiplet pattern observed in the MEGA‐PRESS experiment depends quite strongly on the properties of the slice‐selective refocusing pulses used. Under some circumstance, the central peak can be quite large; this does not necessarily indicate inefficient editing, or a subtraction artifact, but should be recognized as a property of the pulse sequence itself. Magn Reson Med 70:1183–1191, 2013. © 2012 Wiley Periodicals, Inc.