I had an MRI done today on my shoulder. I asked the tech about DTI MRIs and she said they are quite common. The limit is finding a neuro to prescribe it. She said that some high end neuro surgeons and other high end neuros use them but generic neuros tend to not be interested in nor informed about them.

She said there are a number of doctors who spec them locally here in Idaho.
It may help to ask an MRI tech for the name of a neuro who uses them.