The physical phenomenon that MRI is based on does not depend on ionizing radiation, but on other properties of atoms instead. What is this phenomenon called?

gamma-ray bursts

positron emission

X-ray propagation

nuclear magnetic resonance

nuclear magnetic resonance

This phenomenon is called Nuclear Magnetic Resonance.

When I met my future wife, she was working in the medical research building next door to the communications building where I worked. (We shared a parking lot.) MRI was not a thing yet, and she was doing research in Nuclear Magnetic Resonance. I learned a lot about it when I walked next door to visit her in her lab. Strange as it may seem, several years earlier, her older brother was involved in the invention of the CAT scan. When we got married, I figured that our kids had at least a 50% chance of inheriting some brains. So we had some, and they've done OK.