Did doctors really not know or even suspect that CT scans would cause cancer until now?

The studies showing dangers of such “wonder technologies” always seem to come chugging up years after the doctors have been urging them on their patients. They are now predicting thousands more cancer cases for otherwise healthy patients. Where is the “do no harm” credo? http://www.nytimes.com/reuters/2009/12/14/health/news-cancer-radiation.html?scp=2&sq=ct%20scans&st=cse