The imaging method is referred to as Diffusion Weighted Imaging (DWI). A DWI scan with at least 6 different directions can be modeled by a tensor. For this reason, people often refer to DWI scans with very few directions as DWI (e.g. used for clinical Trace images), while a DWI scan with many directions is often referred to as DTI. Indeed, some manufacturers provide different scanner licenses for low direction DWI and high direct scans that they refer to as DTI. As directions increase, one can model with more complex mathematical models, e.g. DSI.