Premium
RF excitation using time interleaved acquisition of modes (TIAMO) to address B 1 inhomogeneity in high‐field MRI
Author(s) -
Orzada Stephan,
Maderwald Stefan,
Poser Benedikt Andreas,
Bitz Andreas K.,
Quick Harald H.,
Ladd Mark E.
Publication year - 2010
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.22527
Subject(s) - excitation , signal (programming language) , radio frequency , amplitude , computer science , field (mathematics) , amplifier , phase (matter) , flip angle , physics , acoustics , head (geology) , nuclear magnetic resonance , optics , magnetic resonance imaging , telecommunications , mathematics , medicine , bandwidth (computing) , quantum mechanics , pure mathematics , radiology , programming language , geomorphology , geology
As the field strength and, therefore, the operational frequency in MRI is increased, the wavelength approaches the size of the human head/body, resulting in wave effects, which cause signal decreases and dropouts. Several multichannel approaches have been proposed to try to tackle these problems, including RF shimming, where each element in an array is driven by its own amplifier and modulated with a certain (constant) amplitude and phase relative to the other elements, and Transmit SENSE, where spatially tailored RF pulses are used. In this article, a relatively inexpensive and easy to use imaging scheme for 7 Tesla imaging is proposed to mitigate signal voids due to B 1 +field inhomogeneity. Two time‐interleaved images are acquired using a different excitation mode for each. By forming virtual receive elements, both images are reconstructed together using GRAPPA to achieve a more homogeneous image, with only small SNR and SAR penalty in head and body imaging at 7 Tesla. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.