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Implementation and evaluation of frequency offset corrected inversion (FOCI) pulses on a clinical MR system
Author(s) -
Payne Geoffrey S.,
Leach Martin O.
Publication year - 1997
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.1910380520
Subject(s) - amplitude , waveform , offset (computer science) , adiabatic process , usable , radio frequency , frequency offset , nuclear magnetic resonance , physics , acoustics , optics , computational physics , computer science , telecommunications , channel (broadcasting) , world wide web , orthogonal frequency division multiplexing , thermodynamics , programming language , quantum mechanics , voltage
FOCI pulses are a variant of hyperbolic secant pulses in which the RF amplitude, RF frequency, and gradient waveform are all modulated by the same function A ( t ). This increases the usable gradient amplitude without requiring a corresponding increase in RF amplitude. In this paper the implementation and inversion profiles of FOCI pulses on a clinical MR system are described, showing improved slice definition and chemical‐shift offset behavior. Their adiabatic behavior is confirmed, and their use with an ISIS sequence for localized MRS is illustrated. Finally the effects of waveform digitization are considered, and the implications for SAR and db/dt are discussed.