The place I called quoted me $6k, but the test from this facility is very detailed as it will tell you the the fractional anisotropy of each white matter tract and whether it is below/above normal or normal. If you are involved in a lawsuit, this would probably be THE test to get.

DTI (Quantitative): An advanced MRI procedure for evaluation of Concussions | Doctors Imaging | MRI, Ultrasound, CT Scan, X-Ray, PET-CT in Metairie

DTI for Traumatic Brain Injury - YouTube

Is there any benefit to getting the test done? Not in terms of treatment as far as I know.