7T vs. 4T: RF power, homogeneity, and signal-to-noise comparison in head images

Signal-to-noise ratio (SNR), RF field (B,), and RF power requirement for hu man head imaging were examined at 7T and 4T magnetic field strengths. The v ariation in B, magnitude was nearly twofold higher at 7T than at 4T (simila r to 42% compared to similar to 23%). The power required for a 90 degrees p ulse in the center of the head at 7T was approximately twice that at 4T, Th e SNR averaged over the brain was at least 1.6 times higher at 7T compared to 4T, These experimental results were consistent with calculations perform ed using a human head model and Maxwell's equations, (C) 2001 Wiley-Liss, I nc.