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A new sequence for shaped voxel spectroscopy in the human brain using 2D spatially selective excitation and parallel transmission
Author(s) -
Waxmann Patrick,
Mekle Ralf,
Schubert Florian,
Brühl Rüdiger,
Kuehne Andre,
Lindel Tomasz D.,
Seifert Frank,
Speck Oliver,
Ittermann Bernd
Publication year - 2016
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3558
Subject(s) - voxel , excitation , imaging phantom , pulse sequence , spectroscopy , computer science , nuclear magnetic resonance , sequence (biology) , physics , human brain , biological system , algorithm , artificial intelligence , optics , chemistry , biology , biochemistry , quantum mechanics , neuroscience
Spatially selective excitation in two dimensions (2D‐SSE) utilizing parallel transmission was applied as a means to acquire signal from voxels adapted to the anatomy of interest for in vivo 1 H MR spectroscopy. A novel method to select spectroscopy voxels with arbitrary shapes in two dimensions was investigated. An on–off scheme with an adiabatic slice selective inversion pulse preceding a 2D‐SSE pulse together with a segmented inward spiral excitation k ‐space trajectory enabled rapid free induction decay acquisitions. Performance of the sequence was evaluated in simulations, phantom experiments, and in vivo measurements at 3 T. High spatial fidelity of the excitation profile was achieved for different target shapes and with little off‐resonance deterioration. Metabolite concentrations in human brain determined with the new sequence were quantified with Cramér–Rao lower bounds less than 20%. They were in the physiological range and did not deviate systematically from results acquired with a conventional SPECIAL sequence. In conclusion, a new approach for shaped voxel MRS in the human brain is presented, which complements existing sequences. Simulations show that 2D‐SSE pulses yield reduced chemical shift artifact when compared with conventional localization methods. Copyright © 2016 John Wiley & Sons, Ltd.