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A radiofrequency coil to facilitate B 1 + shimming and parallel imaging acceleration in three dimensions at 7 T
Author(s) -
Gilbert Kyle M.,
Curtis Andrew T.,
Gati Joseph S.,
Klassen L. Martyn,
Me Ravi S.
Publication year - 2011
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.1627
Subject(s) - physics , electromagnetic coil , radiofrequency coil , cartesian coordinate system , decoupling (probability) , transverse plane , shim (computing) , nuclear magnetic resonance , acoustics , optics , mathematics , geometry , engineering , medicine , structural engineering , quantum mechanics , control engineering , erectile dysfunction
A 15‐channel transmit–receive (transceive) radiofrequency (RF) coil was developed to image the human brain at 7 T. A hybrid decoupling scheme was implemented that used both capacitive decoupling and the partial geometric overlapping of adjacent coil elements. The decoupling scheme allowed coil elements to be arrayed along all three Cartesian axes; this facilitated shimming of the transmit field, B 1 + , and parallel imaging acceleration along the longitudinal direction in addition to the standard transverse directions. Each channel was independently controlled during imaging using a 16‐channel console and a 16 × 1‐kW RF amplifier–matrix. The mean isolation between all combinations of coil elements was 18 ± 7 dB. After B 1 +shimming, the standard deviation of the transmit field uniformity was 11% in an axial plane and 32% over the entire brain superior to the mid‐cerebellum. Transmit uniformity was sufficient to acquire fast spin echo images of this region of the brain with a single B 1 +shim solution. Signal‐to‐noise ratio (SNR) maps showed higher SNR in the periphery vs center of the brain, and higher SNR in the occipital and temporal lobes vs the frontal lobe. Parallel imaging acceleration in a rostral–caudal oblique plane was demonstrated. The implication of the number of channels in a transmit–receive coil was discussed: it was determined that improvements in SNR and B 1 +shimming can be expected when using more than 15 independently controlled transmit–receive channels. Copyright © 2010 John Wiley & Sons, Ltd.