Distributing coil elements in three dimensions enhances parallel transmission multiband RF performance: A simulation study in the human brain at 7 Tesla. Issue 6 (21st March 2016)

• Record Type: Journal Article
• Authors: Wu, Xiaoping; Tian, Jinfeng; Schmitter, Sebastian; Vaughan, J. Tommy; Uğurbil, Kâmil; Van de Moortele, Pierre‐François
• Is Part Of: Magnetic resonance in medicine. Volume 75:Issue 6(2016)
• Page Start: 2464
• Page End: 2472
• Publication Date: 2016-03-21
• Subjects: parallel transmit multiband pulse design -- simultaneous multislice imaging -- transmit B1 homogenization -- high‐field MRI -- multiring RF array design; Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.26194
• Languages: English
• ISSNs: 0740-3194

Abstract

Abstract : 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.