Premium
Phase coherent averaging in magnetic resonance spectroscopy using interleaved navigator scans: Compensation of motion artifacts and magnetic field instabilities
Author(s) -
Thiel Thorsten,
Czisch Michael,
Elbel Gregor K.,
Hennig Juergen
Publication year - 2002
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.10174
Subject(s) - signal (programming language) , laser linewidth , magnetic field , phase (matter) , nuclear magnetic resonance , physics , data acquisition , magnetic resonance imaging , signal averaging , computer science , optics , digital signal processing , radiology , medicine , laser , signal transfer function , quantum mechanics , computer hardware , analog signal , programming language , operating system
Abstract The quality of spectra in 1 H magnetic resonance spectroscopy (MRS) is strongly affected by temporal signal instabilities during the acquisition. One reason for these instabilities are hardware imperfections, e.g., drifts of the main magnetic field in superconducting magnets. This is of special concern in high‐field systems where the specification of the field stability is close to the spectral linewidth. A second major potential source of artifacts, particularly in clinical MRS, is patient motion. Using standard acquisition schemes of phase‐cycled averaging of the individual acquisitions, long‐term effects (field drifts) as well as changes on a shorter time scale (motion) can severely reduce spectral quality. The new technique for volume‐selective MRS presented here is based on the additional interleaved acquisition of a navigator signal during the recovery time of the metabolite acquisition. It corrects for temporal signal instabilities by means of a deconvolution of the metabolite and the navigator signal. This leads to phase‐corrected individual metabolite scans and upon summation to a phase‐coherent averaging scheme. The interleaved navigator acquisition does not require any user interaction or supervision, while sequence efficiency is maintained. Magn Reson Med 47:1077–1082, 2002. © 2002 Wiley‐Liss, Inc.