T2*-based fiber orientation mapping

Neuroimage. 2011 Jul 1;57(1):225-234. doi: 10.1016/j.neuroimage.2011.04.026. Epub 2011 Apr 22.


Recent MRI studies at high field have observed that, in certain white matter fiber bundles, the signal in T(2)*-weighted MRI (i.e. MRI sensitized to apparent transverse relaxivity) is dependent on fiber orientation θ relative to B(0). In this study, the characteristics of this dependency are quantitatively investigated at 7 T using ex-vivo brain specimens, which allowed a large range of rotation angles to be measured. The data confirm the previously suggested variation of R(2)* (=1/T(2)*) with θ and also indicate that this dependency takes the shape of a combination of sin2θ and sin4θ functions, with modulation amplitudes (=ΔR(2)*) reaching 6.44±0.15 Hz (or ΔT(2)*=2.91±0.33 ms) in the major fiber bundles of the corpus callosum. This particular dependency can be explained by a model of local, sub-voxel scale magnetic field changes resulting from magnetic susceptibility sources that are anisotropic. As an illustration of a potential use of the orientation dependence of R(2)*, the feasibility of generating fiber orientation maps from R(2)* data is investigated.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Adult
  • Anisotropy
  • Brain Mapping / methods*
  • Humans
  • Image Processing, Computer-Assisted / methods*
  • Magnetic Resonance Imaging