Diffusion Imaging (DWI and DTI)

Diffusion Weighted Imaging (DWI) contrast is based on the rate of water diffusion in the tissue described by a parameter called apparent diffusion constant (ADC). It is used for evaluation of stroke and many other diseases. Areas which are injured during a stroke show up "darker" on an ADC map compared to healthy tissue.

Diffusion Tensor Imaging (DTI) is used to map the "anisotropy" of the water diffusion in the tissues. This provides a powerful tool to visualize the brain white matter tracts and to assess the changes due to diseases or trauma. Fractional anisotropy (FA) is used to characterize the DTI changes.

A T2*-weighted image, and fractional anisotropy (FA) maps. From left to right: T2*-weighted image, FA map of traumatic brain injury lesion, FA map at 3 months of recovery, and FA map at 6 months of recovery. The circled area highlights the trauma region.