For all intents and purposes, Magneto of Earth-616 has no effective upper limits to his magnetic powers. He is considered an Omega Class mutant, a mutant so powerful, his abilities can affect or even destroy the entire world. His powers are so great he has lifted a 30,000 ton submarine from the depths of the ocean, resisted the force of a nuclear detonation, manipulated electromagnetic fields to generate wormholes to travel through space, and even stripped the adamantium from Wolverine's skeleton, forcefully and painfully. His power defies almost all of the known physics of the Marvel Universe.

Drawing the adamantium from Wolverine's skeleton, yes the material that is supposedly unable to be affected by any normal force in the Marvel Universe once it has set...
Magnetokinesis: Magneto has a near-limitless control of all forms of magnetism, whether natural or artificial, to manipulate any metal. He can manipulate magnetic fields at the planetary level.
Generating Magnetic Force Fields: He is able to generate a forcefield capable of repelling forces equivalent to a nuclear attack. He has successfully defended himself against Thor and his hammer Mjolnir, Iron Man's impressive array of weapons and the wielders of the Phoenix force. He has single-handedly fought against entire teams of heroes and villains.
Magnetic Flight: By connecting himself to the magnetic field of the Earth, Magneto is capable of flight at supersonic speeds. He can also repel himself against the metals in the surface of a planet if the planet has no intrinsic magnetic field.
Molecular matter manipulation: His magnetic field manipulations are so powerful he can reorder the molecular structure of matter by manipulating the electromagnetic force bonds.
His control of his magnetic powers is so precise, he can manipulate the iron in a human's blood, causing aneurysms, strokes or heart attacks. He is even able to create a magnetic field strong enough to suppress the power of thought by suppressing the brain's electromagnetic field. It is likely the same magnetic field which makes him more resistant to psionic abilities.
This is not an all inclusive list of Magneto's powers, it is designed to simply give you a matter of comparison against a device such as an MRI machine; there is NO CONTEST.