Hi my husband had that back in 2009 which was helpful in his diagnosis. From memory it is similar to a MRI and was not a long test I think it was just his head that was in a tunnel but can't be sure as I wasn't in with him. Keep positive.

I’m having a DAT scan on Wednesday. I’ll report back ASAP. I was told 5 hours. Meds first to protect thyroid then wait two hours. Then the injection and wait one hour. Then the test which takes half an hour.

I have had it done for clinical trials. They put a tracer IV in you, you wait for about 4 hours and you have the scan done. It can help immensely with diagnosis.