I know one top tier diagnostic radiologist and he could tell which piece of equipment an image was taken on (or if something is out of calibration) with a fairly quick glance. Regularly on the phone with techs and technologists to get things fixed or reimaged. He retired recently.
From his telling most of the work has been outsourced to India for the last 10-15 years. He only gets the really challenging stuff.
edit: Interestingly, it seems like breast imaging is still done more in house and there are regular reviews, but that's from a different source.