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3D MDEFT imaging of the human brain at 4.7T with reduced sensitivity to radiofrequency inhomogeneity

Thomas, DL; De Vita, E; Deichmann, R; Turner, R; Ordidge, RJ; (2005) 3D MDEFT imaging of the human brain at 4.7T with reduced sensitivity to radiofrequency inhomogeneity. MAGN RESON MED , 53 (6) 1452 - 1458. 10.1002/mrm.20482.

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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 degrees. 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. (c) 2005 Wiley-Liss, Inc.

Type:Article
Title:3D MDEFT imaging of the human brain at 4.7T with reduced sensitivity to radiofrequency inhomogeneity
DOI:10.1002/mrm.20482
Keywords:high field MRI, T-1-weighted imaging, RF inhomogeneity, human brain imaging, structural brain imaging, TO-NOISE RATIO, POWER DEPOSITION, PULSE, OPTIMIZATION, SEQUENCE, FIELDS, COIL, HEAD
UCL classification:UCL > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Neurology > Brain Repair and Rehabilitation
UCL > School of BEAMS > Faculty of Engineering Science > Medical Physics and Bioengineering

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