I've never heard of a SPECT scan either. Honestly, I think that it would be needed to be coordinated with all the other tests & with an analysis of your personality issues & the IRL ways you have of dealing with your life to get a REAL determination. I honestly would never trust one test without all the other testing abilities being coordinated together for a diagnosis.

This might be an interesting article for you to read regarding SPECT scans:
The Neurocritic: The Dark Side of Diagnosis by Brain Scan