Just in case anyone else reads this and is confused. MRIs only use radio waves. No ionizing (or visible or even IR) radiation is used. The strong magnetic fields are a risk (due to interacting with metallic items embedded in the body). The contrast agents also can cause some undesirable side effects.

I'm a bit wary of regular DEXA due to the ionizing radiation. MRIs have essentially zero health side-effects if you're not using any contrast agents.

DEXA is definitely cheaper, but a good amount of my time spent in MRIs was due to assisting in various research and QA projects. Unless you're made of money, I wouldn't recommend that to anyone who has to pay. I wish they were cheaper...