Effects of static and radiofrequency magnetic field inhomogeneity in ultra-high field magnetic resonance imaging

To characterize the severe static (B-0) and radiofrequency (B-1) magnetic field inhomogeneity in ultra-high field (>= 7 T) magnetic resonance imaging, gradient echo (GE) and spin echo (SE) images of in vivo and postmortem human brains were acquired. The B-0 and B-1 inhomogeneity were experimentally mapped and/or numerically simulated, and correlated with the image artifacts. Whereas B-0 inhomogeneity affects predominantly GE images near air/tissue interfaces, B-1 inhomogeneity affects SE images more severely and shows nonintuitive patterns. Mapping of the B-0 and B-1 inhomogeneity is important in characterizing image artifacts. This will help develop better B-0 and B-1 inhomogeneity correction methods. (C) 2006 Elsevier Inc. All rights reserved.