I can't speak for your surgeons, of course, but the whole point of going to titanium was to provide MRI-compatible implants. Even stainless normally thought of as non-magnetic is magnetic at 1.5 or 3T.
Yup.
Well, there's the static field, which is very very (to a few parts per billion) even within the imaging area. Then there's the dynamic (Gradient) fields, in the x,y, and z directions. Those are at mostly audio frequencies, which is why the scans are as noisy as they are.
So. Ring on a finger, dynamic magnetic field, inducing current into...
I can see how that could create _torque_, if the ring was at an angle to the flux lines. Hm. If I still worked there, I'd do a little experiment. Ah well.
Sounds like the same eddy current effect I was describing with the coin, can, and aluminum plate, yup. If that was more portable, it'd be a great bar-bet...