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TROMBONE: T 1 ‐relaxation‐oblivious mapping of transmit radio‐frequency field ( B 1 ) for MRI at high magnetic fields
Author(s) -
Fleysher Roman,
Fleysher Lazar,
Inglese Matilde,
Sodickson Daniel
Publication year - 2011
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.22804
Subject(s) - flip angle , relaxation (psychology) , transmission (telecommunications) , range (aeronautics) , physics , nuclear magnetic resonance , computer science , field (mathematics) , radio frequency , pulse (music) , magnetic resonance imaging , computational physics , optics , materials science , mathematics , telecommunications , medicine , psychology , social psychology , pure mathematics , composite material , radiology , detector
Fast, 3D radio‐frequency transmit field ( B 1 ) mapping is important for parallel transmission, spatially selective pulse design and quantitative MRI applications. It has been shown that actual flip angle imaging—two interleaved spoiled gradient recalled echo images acquired in steady state with two very short time delays (TR 1 , TR 2 )—is an attractive method of B 1 mapping. Herein, we describe the TROMBONE method that efficiently integrates actual flip angle imaging with EPI imaging, alleviates very short TR requirement of actual flip angle imaging and through their synergy yields up to 16 times higher precision in B 1 estimation in the same experimental time. High precision of TROMBONE can be traded for faster scans. The map of B 1 reconstructed from the ratio of intensities of two images is insensitive to longitudinal relaxation time ( T 1 ) in the physiologically relevant range. A table of the optimal acquisition protocol parameters for various target experimental conditions is provided. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.