Counteracting radio frequency inhomogeneity in the human brain at 7 Tesla using strongly modulating pulses

✍ Scribed by N. Boulant; J.-F. Mangin; A. Amadon

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 700 KB
• Volume: 61
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.21955

✦ Synopsis

Abstract

We report flip angle and spoiled gradient echo measurements at 7 Tesla on human brains in three‐dimensional imaging, using strongly modulating pulses to counteract the transmitted radiofrequency inhomogeneity problem. Compared with the standard square pulse results, three points of improvement are demonstrated, namely: (i) the removal of the bright center (typical at high fields when using a quadrature head coil), (ii) the substantial gain of signal in the regions of low B~1~ intensity, and (iii) an increased 35% signal uniformity over the whole brain at the flip angle where maximum contrast between white and gray matter occurs. We also find by means of simulations that standard BIR‐4 adiabatic pulses need several times more energy to reach a similar performance at the same field strength. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.