Yet, they still do use lie detectors, even though the things they detect can be faked, or triggered out of personal alarm or offense. So it is entirely possible, regardless.
It often is "inspired" by what I'm hearing and reading, but not related to how I actually feel about anything in particular. Sometimes I have to put effort into not getting too extreme in those many based-on-a-theme side stories. I'm quite sure this technology would either paint me as someone I'm not, just because of my brain's way of going through a dozen interpretations of whatever it is I'm thinking about, or burn out by the extreme amounts of the internal chatter that entails.
Needless to say, I grew up on nightmares (a common ADHD thing). I eventually ended up learning lucid dreaming to escape them, but still, even my dream world comes up with s##t I would never think of in my waking reality. Those feel so very real to me that I can't imagine this brain scanner thing could tell the difference either.
Prior to this, it was already known to produce false feedback and confessions. The US military has a strange way of repeating history to see if it'll turn out differently "this time." It sadly never does.