DTI Tractography

The Central Nervous System (CNS) is composed of white and gray matter. The gray matter contains the neurons or nerve cells, whereas the white matter consists of fibers coming (afferent) or going (efferent) to different regions of the CNS. These fibers are organized in bundles or "tracts". Previously, few of them could be seen in either in vivo or in brains obtained from autopsies. For that reason their appearence is limited in most neuroanatomy atlases. Their existence has been documented only by techniques that require microscopy.
 

Diffusion Tensor Imaging (DTI) Tractography is a procedure to demonstrate those tracts of the nervous system. This procedure utilizes special techniques of magnetic resonance imaging (MRI), and computer analysis. The tracts are depicted in 2D or 3D images.
 

The MRI sequences utilized to demonstrate the neural tracts look at the symmetry of brain water diffusion. Bundles of fiber tracts make the water diffuse asymmetrically with more "probability" that the diffusion will spread in the direction of the fibers. This asymmetry is termed anisotropy. The more fibers you have, the more anisotropic the water diffusion.