Diffusion tensor imaging

Abstract

It is said that knowledge doubles every 2.5 years. In the field of diagnostic imaging the doubling time is probably shorter due to the rapid pace of technological advances. Diffusion tensor imaging (DTI) and its potential application to neurologic disease represents one such advance. DTI is a special form of diffusion-weighted imaging that allows the assessment and visualization of large white matter fibers on a millimeter-level multidimensional scale.1 Although we can visualize and differentiate white and gray matter with standard MRI pulse sequences, they do not allow us to examine the integrity or directionality of white matter tracts. DTI takes advantage of the diffusivity of water and the restrictions imposed on the diffusion of water by white matter fiber tracts. When fiber tracts are dense, for example, the restriction imposed by their density leads to directionally dependent or anisotropic diffusion. By analogy, if an ink drop is placed in a narrow or oval tube the diffusion of that ink drop will adjust to the shape of the tube. In contrast, if a drop of ink is placed in a large bowl of water the drop of ink will be more spherical …