My memory is not perfect but I seem to recall that there was a controversy over exposing women to mamograms younger than 40 unless there was indicaiton for it. There was an article in the April 5 New Scientist casting doubts on the current standards of "safe" x-rays since finding that cells who have had DNA damage from low dose X-rays do not repair themselves as had been previously thought. If you log onto
www.newscientist.com you might find the full article.