[duskwuff]

> They are superconductors, the resistance is 0.

So long as they stay under their critical temperature. If that changes… well, a lot of liquid helium is about to stop being liquid.

And that's one of the reasons why a permanent-magnet MRI is so interesting -- it doesn't depend on a constant supply of power (for the helium cooler) and gaseous helium (to replace lost gas), so the system is portable, and maintenance costs are likely to be much lower.