Lindy,

I posted previously on the question of interpretation of scans:

http://neurotalk.psychcentral.com/thread149034.html

Also, with reference in particular to spect scans, i was told that if you have several of them, they really need to be done on the same machine, same protocol and same person reading the scan, to have any real validity of comparison.

And on a not so minor point - I was once given someone else's MRI to take away from the clinic to my neurologist. Luckily i checked the name on the side of the film myself.