Re: Brain scans?
Vax did - not because he's trying to help the Derleth cause, but because for all he knows it'll help him make some sense out of the hows and whys he was taken to the Dreamlands and why he's truly back now. Everyone involved in the scanning can just let him think so, it'll be easiest.
Yelena did too, because why the hell not? She's already had her mind messed with enough, a little more probably won't hurt.