Diffusion Tensor Imaging (DTI) is a method of imaging that maps the diffusion, or movement, of molecules in the brain--mainly water. This movement can give insight into any structural abnormalities in the brain, especially changes in white matter. White matter is made primarily of neuronal tracts, which are responsible for the communication of one brain area with another. DTI can give insight into structural abnormalities that could be the cause of prolonged behavioral and mental changes following a head injury. Typically, an acute concussion does not cause changes in white matter structure that are identifiable through DTI, therefore this test is normally recommended only for a small subset of patients with concussion. For example, DTI studies may be requested for those who are experiencing a clinically significant level of symptoms over a period of time, for those with a history of multiple concussions, or for those who may have had a potentially undiagnosed TBI or micro-bleed in the brain.