I had an MRI roughly a month after my left nipple was pierced. My piercer removed my ear jewelry for me the day before the MRI, but I removed my nipple CBR at the MRI site.
Immediately after finishing the MRI, I went to my vehicle where I struggled to replace the CBR in my not-yet-healed nipple. It wasn’t easy. At one point I glanced up to see an elderly couple gawking at me. They obviously had no idea what I was doing. A penny for their thoughts!
I have acrylic or bone/shell thingies for my various piercings. My ears are gauged to 10 ga, normally I wear captive ball hoops but I will swap in nonmetallic stuff. I keep a pack ofthese in the assorted gauge pack and alcohol swabs on hand for people who might need them.
I once saw a guy in DFW with (short, blunt) metal horns, which I assume were screwed onto non-removable bases implanted in his forehead. Maybe the bases are plastic so he could unscrew the horns and send them through security in a bin, but otherwise, I figure they just wanded his head.