If you got them from a hospital, they were most likely used in radiology. If you got them anywhere else, you'll have to narrow it down by that origin. You say cylinders? Do they have holes on both ends? If they're containers, they won't allow radition to penetrate. Kind of useless in radiology, unless you place your testicles in one during an xray. If they ring when dropped, I would say trash them. They could have been used for counter weights of some kind and not for radiology at all.