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Distributing coil elements in three dimensions enhances parallel transmission multiband RF performance: A simulation study in the human brain at 7 Tesla
Author(s) -
Wu Xiaoping,
Tian Jinfeng,
Schmitter Sebastian,
Vaughan J. Tommy,
Uğurbil Kâmil,
Van de Moortele PierreFrançois
Publication year - 2016
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.26194
Subject(s) - parallel communication , sagittal plane , specific absorption rate , transmission (telecommunications) , radiofrequency coil , electromagnetic coil , radio frequency , excitation , stripline , materials science , ring (chemistry) , coronal plane , nuclear magnetic resonance , computer science , optics , physics , telecommunications , antenna (radio) , chemistry , radiology , organic chemistry , medicine , quantum mechanics
Purpose We explore the advantages of using a double‐ring radiofrequency (RF) array and slice orientation to design parallel transmission (pTx) multiband (MB) pulses for simultaneous multislice (SMS) imaging with whole‐brain coverage at 7 Tesla (T). Methods A double‐ring head array with 16 elements split evenly in two rings stacked in the z ‐direction was modeled and compared with two single‐ring arrays consisting of 8 or 16 elements. The array performance was evaluated by designing band‐specific pTx MB pulses with local specific absorption rate (SAR) control. The impact of slice orientations was also investigated. Results The double‐ring array consistently and significantly outperformed the other two single‐ring arrays, with peak local SAR reduced by up to 40% at a fixed excitation error of 0.024. For all three arrays, exciting sagittal or coronal slices yielded better RF performance than exciting axial or oblique slices. Conclusions A double‐ring RF array can be used to drastically improve SAR versus excitation fidelity tradeoff for pTx MB pulse design for brain imaging at 7 T; therefore, it is preferable against single‐ring RF array designs when pursuing various biomedical applications of pTx SMS imaging. In comparing the stripline arrays, coronal and sagittal slices are more advantageous than axial and oblique slices for pTx MB pulses. Magn Reson Med 75:2464–2472, 2016. © 2016 Wiley Periodicals, Inc.