2017 Volume 63 Issue 4 Pages 285-292
Diffusion magnetic resonance imaging (dMRI), which was established in the mid 1980’s, is an imaging technique that is based on the diffusion of water molecules in tissue. Initially it was an isotropic diffusion-weighted imaging (DWI) technique, and has been widely used mainly for investigating the tissue microstructural changes in neurological abnormalities, especially ischemic stroke. Many studies have been conducted to validate the usefulness of DWI in clinical settings and to improve the technique. Diffusion tensor imaging (DTI) was later introduced to deal with the anisotropic diffusion; the use of an ellipsoid tensor model means that the size and the direction of the water diffusion can be delineated. DTI and its developments are becoming powerful tools, and have become the standard imaging techniques for analyzing white matter fiber structure and connectivity in vivo. Furthermore, to facilitate researchers in applying DTI for multi-subject studies, tract-based spatial statistics (TBSS) was developed. TBSS is a voxelwise statistical analysis that was originally used to evaluate the fractional anisotropy (FA) values in the white matter. Thereafter, diffusion kurtosis imaging (DKI) was developed to overcome the limitations of DTI such as the non-Gaussian characteristics of tissue and the crossing fiber problems. The latest promising technique is neurite orientation dispersion and density imaging (NODDI), which can be used to show the microstructural changes of brain tissue more sensitively and specifically.
