The latest research in ADD scan studies show a lack on activity in the left side of the pre-frontal cortex. As far as your question goes not everyone can afford these scans to come up with an accurate diagnosis. Also a SPECT scan could show a two totally different patterns in activity if the scan was done more than once. It would have to take numerous scans over time to come up with an accurate diagnosis. That is why it is much easier to be honest about symptoms with a psychiatrist you trust.
David Lopez Blass