title: 7T vs. 4T: RF power, homogeneity, and signal-to-noise comparison in head images.
abstract: Signal-to-noise ratio (SNR), RF field (B(1)), and RF power requirement for human head imaging were examined at 7T and 4T magnetic field strengths. The variation in B(1) magnitude was nearly twofold higher at 7T than at 4T ( approximately 42% compared to approximately 23%). The power required for a 90 degrees pulse in the center of the head at 7T was approximately twice that at 4T. The SNR averaged over the brain was at least 1.6 times higher at 7T compared to 4T. These experimental results were consistent with calculations performed using a human head model and Maxwell's equations. Magn Reson Med 46:24-30, 2001.
authors.affiliation: Center for MR Research, Department of Radiology, School of Medicine, University of Minnesota, 2021 Sixth Street SE, Minneapolis, MN 55455, USA. tommy@cmrr.umn.edu
authors.forename: J T
authors.initials: JT
authors.lastname: Vaughan
authors.forename: M
authors.initials: M
authors.lastname: Garwood
authors.forename: C M
authors.initials: CM
authors.lastname: Collins
authors.forename: W
authors.initials: W
authors.lastname: Liu
authors.forename: L
authors.initials: L
authors.lastname: DelaBarre
authors.forename: G
authors.initials: G
authors.lastname: Adriany
authors.forename: P
authors.initials: P
authors.lastname: Andersen
authors.forename: H
authors.initials: H
authors.lastname: Merkle
authors.forename: R
authors.initials: R
authors.lastname: Goebel
authors.forename: M B
authors.initials: MB
authors.lastname: Smith
authors.forename: K
authors.initials: K
authors.lastname: Ugurbil
mesh_terms: D001921:Brain / Q000033:anatomy & histology*; D002138:Calibration; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D011846:Radio Waves