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Real‐time motion and B 0 corrected single voxel spectroscopy using volumetric navigators
Author(s) -
Hess Aaron T.,
Dylan Tisdall M.,
Andronesi Ovidiu C.,
Meintjes Ernesta M.,
van der Kouwe André J. W.
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.22805
Subject(s) - shim (computing) , laser linewidth , nuclear magnetic resonance , voxel , magnetic resonance imaging , population , nuclear medicine , computer science , optics , physics , artificial intelligence , radiology , medicine , surgery , erectile dysfunction , laser , environmental health
In population groups where head pose cannot be assumed to be constant during a magnetic resonance spectroscopy examination or in difficult‐to‐shim regions of the brain, real‐time volume of interest, frequency, and shim optimization may be necessary. We investigate the effect of pose change on the B 0 homogeneity of a (2 cm) 3 volume and observe typical first‐order shim changes of 1 μT/m per 1° rotation (chin down to up) in four different volumes of interest in a single volunteer. An echo planar imaging volume navigator was constructed to measure and apply in real‐time within each pulse repetition time: volume of interest positioning, frequency adjustment, and first‐order shim adjustment. This volume navigator is demonstrated in six healthy volunteers and achieved a mean linewidth of 4.4 Hz, similar to that obtained by manual shim adjustment of 4.9 Hz. Furthermore, this linewidth is maintained by the volume navigator at 4.9 Hz in the presence of pose change. By comparison, a mean linewidth of 7.5 Hz was observed, when no correction was applied. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.