How doesn't the magnet changing the position of your bodies protons hurt you in an mri?

Question

from what i understand, an mri works by attracting your bodies charged protons and then letting them go back in their regular positions and using computers to show the body by using the time it takes for the protons to return to their positions. like it takes longer in fat cells than in muscle cells etc. i don't know if my understanding is correct though. if it is true that the magnet moves your bodies protons, how don't you feel that? is it because there aren't enough to feel? please explain.

*don't answer the question if you don't really know the answer please*

Answer 1

It doesn't move the protons how you're thinking. Instead, it changes the magnetic alignment of the nucleus of hydrogen atoms in the water in the body. The change in nuclear magnetic orientation changes the response to changing magnetic field direction;  radio waves are used to scope the changes in nuclear alignment. Since different tissues have different water concentrations, you end up with a contrast image of the internal structures.

So you're not actually "pulling" hydrogen (protons) out of the body, you're just changing how their nuclei spin. But, if you had an object in your body that reacts strongly in magnetic fields (i.e. a nail, a bullet, etc) then that object would be pulled out of the body. Since hydrogen atoms are non-magnetic, they don't physically move out of the body, so you don't feel anything in an MRI.

If you want to know more, read about NMR spectroscopy (nuclear magnetic resonance, which this technology is based on) and MRI's; both are available in wikipedia.