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Transmit and receive RF fields determination from a single low‐tip‐angle gradient‐echo scan by scaling of SVD data
Author(s) -
Sbrizzi Alessandro,
Raaijmakers Alexander J. E.,
Hoogduin Hans,
Lagendijk Jan J. W.,
Luijten Peter R.,
Berg Cornelis A. T.
Publication year - 2014
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.24912
Subject(s) - singular value decomposition , scaling , echo (communications protocol) , physics , voxel , multipole expansion , optics , nuclear magnetic resonance , algorithm , mathematics , computer science , geometry , artificial intelligence , computer network , quantum mechanics
Purpose A new method, called Transmit and Receive Patterns from Low‐Tip‐angle gradient‐Echo Images (TRIPLET), is described which simultaneously maps theB 1 +andB 1 −fields of a transmit/receive radiofrequency coil array. The input data are low‐tip‐angle gradient‐echo images, which can be acquired in a relatively short scanning time. Theory and Methods For each voxel in the field of view, a matrix can be assembled with the low‐tip‐angle gradient‐echo image values of the radiofrequency coil array. Applying the singular value decomposition to those matrices, datasets are obtained which show a high resemblance with the trueB 1 +andB 1 −fields. These datasets are a voxel‐wise scaled version of the true radiofrequency maps. The channel independent scaling parameters can be found by implicitly forcing the reconstructed fields to be solutions of the Maxwell equations. This is achieved by introducing a multipole expansion consisting of Bessel/Fourier functions. Results Two FDTD simulated radiofrequency fields for two coil array combinations at 7 T and a measured, in vivo dataset at 7 T are investigated to illustrate the singular value decomposition analysis of the low‐tip‐angle gradient‐echo images and to show how theB 1 +andB 1 −fields can be reconstructed by Transmit and Receive Patterns from Low‐Tip‐angle gradient‐Echo Images. Conclusion The Transmit and Receive Patterns from Low‐Tip‐angle gradient‐Echo Images algorithm can convert the datasets from singular value decomposition analysis of low‐tip‐angle gradient‐echo images to trueB 1 +andB 1 −fields. Magn Reson Med 72:248–259, 2014. © 2013 Wiley Periodicals, Inc.