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Quantitative single‐voxel spectroscopy: The reciprocity principle for receive‐only head coils
Author(s) -
Jost Gregor,
Harting Inga,
Heiland Sabine
Publication year - 2005
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.20236
Subject(s) - electromagnetic coil , voxel , flip angle , reciprocity (cultural anthropology) , nuclear magnetic resonance , signal (programming language) , head (geology) , acoustics , radiofrequency coil , physics , calibration , scanner , optics , materials science , magnetic resonance imaging , computer science , artificial intelligence , radiology , medicine , psychology , social psychology , quantum mechanics , geomorphology , programming language , geology
Purpose To correct MR spectra for local changes in the coil sensitivity for a widely used coil setup, consisting of a transmitting body coil and a receive‐only head coil. Materials and Methods The method relies on the reciprocity principle for the body coil and a correction factor for signal amplitudes between body coil and head coil. The correction is based either on the local flip angle dependence of the stimulated echo acquisition mode signal (TFC) or on the automatic RF calibration (RFC). Water phantoms of different volumes were used to simulate variable coil loads, and B1 field inhomogeneities were assessed by varying the voxel position. Furthermore, the correction was tested by longitudinal measurements in one volunteer. Results The correction in vitro yields a reduction of the variation coefficient of the water signal by about 77% (TFC) and 66% (RFC) for different coil loads, as well as 55% (TFC) for variable voxel positions. Slightly lower reductions were assessed for the variation coefficients of the metabolite signals in vivo. Conclusion This approach adequately compensates for local changes in coil sensitivity, when acquiring MR spectra with a receive‐only head coil. J. Magn. Reson. Imaging 2005;21:66–71. © 2004 Wiley‐Liss, Inc.