In case it’s not 100% clear–the scans don’t last 4 and 24 hours, it’s the time lapsed from the injection. Pretty much the scans range from 45 minutes to an hour, with a couple different scans per session. If something needs more follow-up, there can also be 48 and 72-hour scans, as well.

During the first day while trying not to freak out as that huge machine towered over me (and revolved around me at one point, but not smoothly, more a ca-chunk, pause, ca-chunk, pause kinda deal) my arms had to be out of the way so were raised above my head. The numbness from the position wasn’t helped by the temps in that (and most other) scan room.