At Doug Saito's seminar his theory was: If you add to the chip you are altering it, if you subtract, (CLEANING), you are not. Several years ago I and others also considered X-RAYING some chips, the alteration shows up because of different densities. I did this on some HIGH END chips, used my dentitst who really liked the idea and we found nothing, Allan Meyers has published some results of X-RAYING which are very interesting!