I did a lot of cardiac MR and often GA cases. Sometimes after the scan an echo would be done.

I know my anatomy and etc and have done a short stint in ultrasound. I have no idea what you are doing or looking at and can identify pretty much nothing.

Echo techs are going to be around a lot longer than MR techs.

I mean, probably not. No expert, but everytime I go to an immunology meeting (I'm a paediatrician) they've got a whole stack of new diseases. The field is moving fast, and there has to be a careful amount of shared decision making about when to test, what a positive test means and so on. I reckon they're as safe as any of us.