Recent Developments in Diffusion Tensor Imaging of Brain.
Diffusion Weighted Imaging is a powerful Magnetic Resonance Imaging technique from a clinical standpoint, as the inherent rate of diffusion within various regions of the body can be measured. Stejskal and Tanner first described the technique to measure water diffusion with Nuclear Magnetic Resonance in 1965.
Water molecules in the body encounter physical boundaries that impede their random displacement, i.e. molecules can hit a barrier and bounce back within the given diffusion time of the experiment. Thus, the resultant signal may be higher than if the sample were under the same conditions but without barriers resulting in lower rates of diffusion than actuality.
DWI provides a powerful diagnostic tool as different diseases and disease states result in differential imbalances in local water content and diffusivity rates. Diffusion in the central nervous system may not be isotropic i.e. diffusion is not the same in all directions.
Diffusion in white matter tracts is preferential in the direction of the fibers and very small perpendicular to the fiber. Thus white matter bundles within the brain exhibit high degrees of anisotropy within a given voxel. Signal intensity, in diffusion-weighted images of white matter, changes depending on the direction of the applied diffusion gradient, due to the preferential direction of diffusion within the fibers, thus offering a means of determining fiber orientation.
Radiol Open J. 2015; 1(1): 1-12. doi: 10.17140/ROJ-1-101
