Are you worried it will show cancer? If by a slim chance, it does, then you could get it treated and dealt with. MRIs do not cause cancer. If they did, then I'd be dead a long time ago! I think I've about paid for one machine.
You'll just need to stick your leg in. Your head will be out. It's just sort of noisy, sounding like someone's tearing up a street with a jack hammer sometimes. I've usually been given earphones, so I can listen to music, at least when I've had to stick my whole body into the thing.
It'll be okay. I have GAD and sailed through. You will, too!