The effect of susceptibility differences on an MR image is known to increase with field strength. Magnetic field inhomogeneities within the voxels influence the apparent transverse relaxation time T(2) *, while effects due to different precession frequencies between voxels caused by local field variations are evident in the image phase, and susceptibility-weighted imaging highlights the veins and deep brain structures. Here, these three contrast mechanisms are examined at a field strength of 9.4 T. The T(2) * maps generated allow the identification of white matter structures not visible in conventional images. Phase images with in-plane resolutions down to 130 μm were obtained, showing high gray/white matter contrast and allowing the identification of internal cortical structures. The susceptibility-weighted images yield excellent visibility of small venous structures and attain an in-plane resolution of 175 μm.
Copyright © 2010 Wiley-Liss, Inc.