Yes, I believe I've put my baggage through said CBP x-rays while in secondary (agriculture) screening.

I suppose I'm wondering whether I ought to have taken (or take, in the future) any precautions with these machines. Other than certain types of photo film (which I don't use) is there any chance these specialized x-rays are harmful to our belongings?

Can one even opt-out of these x-rays (e.g., requesting inspection by hand)?