The thought crossed my mind, to be sure! I talked about all that with the techs beforehand. "Are you sure this isn't going to yank my teeth out?" "Pretty sure. Now stop moving around."
I have a simple hiatal hernia. One of the treatment options is to basically put a weighted band around your esophagus above the stomach so that the weight holds everything downward so your stomach doesn't get pulled up through the hernia. I imagined being in a car accident or some other situation where I'm nonresponsive, the doctor ordering an MRI, and me re-enacting the scene from Alien. Nah, I'll take my chances with the hernia, thanks.
Well - if it helps any - my understanding is that a doctor at an ER center would order a CT scan which is based on x-rays and can be done in a matter of a few minutes.
MRI scans are really reserved for things that don't image well on CT scans or when the resolution of a CT scan just isn't good enough. They also take quite a bit of time to perform.