An MRI is just a great big magnet (generated by a superconductor that is held at low temperatures by liquid helium).
From the safety section of the wiki: "Since MRI does not use any ionizing radiation, its use is generally favored in preference to CT when either modality could yield the same information... MRI uses powerful magnets and can therefore cause magnetic materials to move at great speeds, posing a projectile risk, and may cause [extremely rare, perhaps fatal] accidents."
If you've had a PET scan, then you've been exposed to antimatter (anti-electrons) for Positron Emission Tomography (which ends up as gamma ray radiation).
A magnetic field is not radiation. The changing RF fields used are, but they're not ionizing radiation (the dangerous kind) like that found in CT scans. The radiation used in MRIs should not be able to induce any changes to the molecular structure of your body, but RF burns can still be a risk. (Clothing and even tattoo ink can exacerbate this, fascinating!) The biggest risk seems to be being bonked by loose medical equipment, but I don't think that's what you were asking about.
There is a theory that there could be unexplored effects of RF exposure. For example, we can see that glucose metabolism increases in brain tissue exposed to RF. That could be the end of it, or there could be consequences to that under the right conditions. We don't know yet.
Very strong constant magnetic fields don't seem to be dangerous (at least at the kind of levels MRI machines work at, which are within an order of magnitude of the strongest magnets on the planet). A very rapidly changing strong magnetic field can be dangerous, because it induces currents in your body, like in your nerves. There are safety limits (very conservatively set) in MRI machines on how quickly they adjust magnetic fields, as if they were to really go for it there's a risk of heart problems (in the moment, it's not like CT scans where more exposure means more risk later in life).
We don't have any evidence they are dangerous. There are some phenomenon like magnetophosenes. You could also look up what a magnetar would theoretically do to a body, but nobody is getting close to one of them anytime soon.
not at all whatsoever. however if you have gadolinium injected for contrast some people have problems with that. but the magnetic field itself doesn't affect you negatively on its own
https://en.wikipedia.org/wiki/CT_scan
An MRI is just a great big magnet (generated by a superconductor that is held at low temperatures by liquid helium).
From the safety section of the wiki: "Since MRI does not use any ionizing radiation, its use is generally favored in preference to CT when either modality could yield the same information... MRI uses powerful magnets and can therefore cause magnetic materials to move at great speeds, posing a projectile risk, and may cause [extremely rare, perhaps fatal] accidents."
https://en.wikipedia.org/wiki/Magnetic_resonance_imaging
If you've had a PET scan, then you've been exposed to antimatter (anti-electrons) for Positron Emission Tomography (which ends up as gamma ray radiation).
https://en.wikipedia.org/wiki/Positron_emission_tomography