If J doesn't evolve, it won't J-resolve: J-PRESS with bandwidth-limited refocusing pulses

There is increasing interest in the J‐PRESS technique, an in vivo implementation of two‐dimensional J‐spectroscopy combined with PRESS localization, for high‐field spectroscopy studies of the human brain. The experiment is designed to resolve scalar couplings in the second, indirectly detected dimen...

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Bibliographic Details
Published in:Magnetic resonance in medicine 2011-06, Vol.65 (6), p.1509-1514
Main Authors: Edden, Richard A. E., Barker, Peter B.
Format: Article
Language:English
Subjects:
Aspartic Acid - analogs & derivatives
Aspartic Acid - metabolism
Brain - metabolism
Brain Mapping - methods
chemical shift displacement
Computer Simulation
gamma-Aminobutyric Acid - metabolism
Humans
J-PRESS
J-refocused
J-resolved
Lactates - metabolism
Magnetic Resonance Spectroscopy - instrumentation
Magnetic Resonance Spectroscopy - methods
Phantoms, Imaging
scalar coupling
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Summary:There is increasing interest in the J‐PRESS technique, an in vivo implementation of two‐dimensional J‐spectroscopy combined with PRESS localization, for high‐field spectroscopy studies of the human brain. The experiment is designed to resolve scalar couplings in the second, indirectly detected dimension, but will only do so if the slice‐selective refocusing pulses in the PRESS sequence affect all coupled spins equally. At high magnet field strengths, due to limited RF pulse bandwidth, PRESS‐based localization results in spatially dependent evolution of coupling. In some regions of the localized volume, coupling evolves during the PRESS echo time, while in other regions it may be partially or fully refocused. This study investigates the impact of this effect on the appearance of the J‐PRESS spectrum for coupled spins, focusing on two commonly observed metabolites, lactate and N‐acetyl aspartate, showing that such behavior results in additional peaks in the J‐resolved spectrum (termed J‐refocused peaks). It is also demonstrated that increasing the bandwidth of refocusing pulses significantly reduces the size of such signals. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
ISSN:0740-3194
1522-2594
DOI:10.1002/mrm.22747