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3D MDEFT imaging of the human brain at 4.7 T with reduced sensitivity to radiofrequency inhomogeneity
Author(s) -
Thomas David L.,
De Vita Enrico,
Deichmann Ralf,
Turner Robert,
Ordidge Roger J.
Publication year - 2005
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.20482
Subject(s) - flip angle , excitation , adiabatic process , amplitude , nuclear magnetic resonance , signal (programming language) , pulse (music) , pulse sequence , fourier transform , sensitivity (control systems) , physics , materials science , intensity (physics) , optics , computational physics , magnetic resonance imaging , computer science , medicine , quantum mechanics , electronic engineering , detector , radiology , programming language , engineering , thermodynamics
Abstract A modification to the 3D modified driven equilibrium Fourier transform (MDEFT) imaging technique is proposed that reduces its sensitivity to RF inhomogeneity. This is especially important at high field strengths where RF focusing effects exacerbate B 1 inhomogeneity, causing significant signal nonuniformity in the images. The adiabatic inversion pulse used during the preparation period of the MDEFT sequence is replaced by a hard (nonadiabatic) pulse with a nominal flip angle of 130°. The spatial inhomogeneity of the hard pulse preparation compensates for the inhomogeneity of the excitation pulses. Uniform signal intensity is obtained for a wide range of B 1 amplitudes and the high CNR characteristic of MDEFT is retained. The new approach was validated by numerical simulations and successfully applied to human brain imaging at 4.7 T, resulting in high‐quality T 1 ‐weighted images of the whole human brain at high field strength with uniform signal intensity and contrast, despite the presence of significant RF inhomogeneity. Magn Reson Med 53:1452–1458, 2005. © 2005 Wiley‐Liss, Inc.