A method for myelin fiber orientation mapping using diffusion-weighted MR images.
In the past, the anisotropic diffusion of water molecules in white matter in the brain has been correlated to the basic symmetry of the myelin fibers: water diffuses more readily along the fiber direction than perpendicular to it. As a consequence, diffusion sensitized magnetic resonance imaging can be expected to be useful for studying the fiber orientation. In this work, we present a method for exploiting this type of information to map the fiber orientations in the image plane. It makes use of three diffusion-weighted images with sensitizing gradients along x, y and u, an axis at 45 degrees with respect to x and y. The orientation information contained in these images is summarized in a single image representing the angle between the fiber direction and a fixed axis, making use of a cyclic color scale. The method is evaluated using computer simulations for a variety of diffusion weighting strengths and signal-to-noise ratios, tested on a phantom and illustrated on an in vivo example. An extension to the determination of the fiber orientation in three dimensions is also described.
Coremans
J
J
Biomedical MR Unit, PRIMIS, Vrije Universiteit Brussel, Belgium.
Luypaert
R
R
Verhelle
F
F
Stadnik
T
T
Osteaux
M
M
D016880:Anisotropy; D001921:Brain / Q000166:cytology*; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D008961:Models, Structural; D009413:Nerve Fibers, Myelinated