What Does A DOT Test Reveal About Parkinson S Disease?

My neurologist has recommended a DOT test. He said it was a nuclear test. I think he suspects Parkinson disease. I have complained of balance issues for over a year, but I do not fall. I recently had a CT scan (short version), a brain MRI and an EEG. What will the DOT test show? What is the full name for the DOT test? Thanks