Journal Article

T2-based fiber orientation mapping

Duyn, Jeff H., Kuo, Li-Wei, Silva, Afonso C., Lee, Jongho, Merkle, Hellmut, van Gelderen, Peter

2011

Overview

Recent MRI studies at high field have observed that, in certain white matter fiber bundles, the signal in T2⁎-weighted MRI (i.e. MRI sensitized to apparent transverse relaxivity) is dependent on fiber orientation θ relative to B0. In this study, the characteristics of this dependency are quantitatively investigated at 7T using ex-vivo brain specimens, which allowed a large range of rotation angles to be measured. The data confirm the previously suggested variation of R2⁎ (=1/T2*) with θ and also indicate that this dependency takes the shape of a combination of sin2θ and sin4θ functions, with modulation amplitudes (=ΔR2⁎) reaching 6.44±0.15Hz (or ΔT2⁎=2.91±0.33ms) 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 R2⁎, the feasibility of generating fiber orientation maps from R2⁎ data is investigated. [Display omitted] ► Demonstrate orientation dependent T2* in white matter of fixed human brain. ► Present a susceptibility anisotropy model that closely matches to the T2* measurement. ► Present a novel fiber orientation map based on T2* and compare it with DTI.

• Publisher: Elsevier Inc
• Subject: Adult / Anisotropy / Brain Mapping - methods / Diffusion tensor imaging (DTI) / Fiber tracking / Humans / Image Processing, Computer-Assisted - methods / Magnetic Resonance Imaging / Magnetic susceptibility anisotropy in white matter / R2 / Susceptibility tensor imaging (STI) / T2⁎ relaxation