dr. david larson and his team at cincinnati children's hospital published the study, out today in the journal "radiology." >> what we found was from 1995 to 2008 the number of ct scans that were done in children who visited the emergency department increased fivefold, essentially, from 330,000 per year to 1.65 million per year. >> reporter: to get those images the ct scan takes multiple x-rays. and that has consequences. a typical ct scan exposes a child to about 100 times as much radiation as a conventional x-ray. experts say this can present a danger to adults but it is far more of a problem for children. >> radiation in children scares us. it's the fact that they're small little creatures and they have a long life to live. and the chance of them getting cancer from that increases exponentially. >> reporter: but doctors emphasize there is a risk-benefit ratio, that sometimes the ct scan is definitely called for and can be an enormously helpful tool. general electric, part owner of nbc universal, is one of the biggest manufacturers of ct scanners. often, doctors say, using the device is a ba