[chasil]

I didn't really know this, but a Computed Tomography scan uses X-rays.

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