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Adiabatic RF pulse design for Bloch‐Siegert B + mapping
Author(s) -
Khalighi Mohammad Mehdi,
Rutt Brian K.,
Kerr Adam B.
Publication year - 2013
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.24507
Subject(s) - adiabatic process , pulse (music) , imaging phantom , specific absorption rate , sensitivity (control systems) , physics , nuclear magnetic resonance , bloch equations , noise (video) , computational physics , optics , computer science , telecommunications , electronic engineering , quantum mechanics , engineering , detector , antenna (radio) , artificial intelligence , image (mathematics)
The Bloch–Siegert (B–S) B 1 + mapping method has been shown to be fast and accurate, yet it suffers from high Specific Absorption Rate (SAR) and moderately long echo time. An adiabatic RF pulse design is introduced here for optimizing the off‐resonant B–S RF pulse to achieve more B–S B 1 + measurement sensitivity for a given pulse width. The extra sensitivity can be used for higher angle‐to‐noise ratio B 1 + maps or traded off for faster scans. Using numerical simulations and phantom experiments, it is shown that a numerically optimized 2‐ms adiabatic B‐S pulse is 2.5 times more efficient than a conventional 6‐ms Fermi‐shaped B–S pulse. The adiabatic B–S pulse performance is validated in a phantom, and in vivo brain B 1 + mapping at 3T and 7T are shown. Magn Reson Med 70:829–835, 2013. © 2012 Wiley Periodicals, Inc.