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Comparison of RF body coils for MRI at 3 T: a simulation study using parallel transmission on various anatomical targets
Author(s) -
Wu Xiaoping,
Zhang Xiaotong,
Tian Jinfeng,
Schmitter Sebastian,
Hanna Brian,
Strupp John,
Pfeuffer Josef,
Hamm Michael,
Wang Dingxin,
Nistler Juergen,
He Bin,
Vaughan Thomas J.,
Ugurbil Kamil,
Moortele PierreFrancois Van
Publication year - 2015
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.3378
Subject(s) - magnetic resonance imaging , medical school , medicine , siemens , research center , center (category theory) , nuclear medicine , library science , medical physics , radiology , physics , computer science , medical education , pathology , chemistry , quantum mechanics , crystallography
The performance of multichannel transmit coil layouts and parallel transmission (pTx) RF pulse design was evaluated with respect to transmit B 1 ( B 1 + ) homogeneity and specific absorption rate (SAR) at 3 T for a whole body coil. Five specific coils were modeled and compared: a 32‐rung birdcage body coil (driven either in a fixed quadrature mode or a two‐channel transmit mode), two single‐ring stripline arrays (with either 8 or 16 elements), and two multi‐ring stripline arrays (with two or three identical rings, stacked in the z axis and each comprising eight azimuthally distributed elements). Three anatomical targets were considered, each defined by a 3D volume representative of a meaningful region of interest (ROI) in routine clinical applications. For a given anatomical target, global or local SAR controlled pTx pulses were designed to homogenize RF excitation within the ROI. At the B 1 + homogeneity achieved by the quadrature driven birdcage design, pTx pulses with multichannel transmit coils achieved up to about eightfold reduction in local and global SAR. When used for imaging head and cervical spine or imaging thoracic spine, the double‐ring array outperformed all coils, including the single‐ring arrays. While the advantage of the double‐ring array became much less pronounced for pelvic imaging, with a substantially larger ROI, the pTx approach still provided significant gains over the quadrature birdcage coil. For all design scenarios, using the three‐ring array did not necessarily improve the RF performance. Our results suggest that pTx pulses with multichannel transmit coils can reduce local and global SAR substantially for body coils while attaining improved B 1 + homogeneity, particularly for a “ z ‐stacked” double‐ring design with coil elements arranged on two transaxial rings. Copyright © 2015 John Wiley & Sons, Ltd.