Premium
If J doesn't evolve, it won't J‐resolve: J‐PRESS with bandwidth‐limited refocusing pulses
Author(s) -
Edden Richard A. E.,
Barker Peter B.
Publication year - 2011
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.22747
Subject(s) - spins , bandwidth (computing) , physics , pulse sequence , nuclear magnetic resonance , spectroscopy , coupling (piping) , scalar (mathematics) , optics , computer science , condensed matter physics , materials science , quantum mechanics , telecommunications , mathematics , geometry , metallurgy
Abstract 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.