Using CT scans to diagnose head injuries in children may needlessly expose them to radiation. And the scans also don't catch minor injuries any better than observing the child, according to a new study in the latest issue of Pediatrics. But good luck getting your local emergency room to back off of them. They've become the go-to test for quickly diagnosing soft-tissue injuries, like bleeding on the brain, that won't show up in an X-ray. And half of all children who go to an emergency room with a head injury now get CT scans, according to Lise Nigrovic, an attending physician in the emergency room at Children's Hospital Boston who led the study.