MRIs aren't much use for screening. They can't be used to diagnose many diseases at all, and for many others, their sensitivity and specificity are quite low. In addition, they produce a large number of huge, highly complex images that have to be reviewed by a human being, and it's incredibly easy to overlook something if you don't know what to look for. If I had a coffee for every time our radiology specialist has said some variant of "I wouldn't even have noticed that if I didn't know that's where the pain is -" well, let's just say, I'd find it a lot easier not to fall asleep in the radiology demonstration.

If you want one yearly screening procedure available to anyone, there are many better choices than MRIs, especially considering their high costs (even in non-US countries.)