I wonder that also. My 4 months old fell on his head and the doctors said it's our decision if we want a cat scan. They said he looks ok, but they can never be 100% sure, but studies have showed that babies that had a cat scan at a very young age are more likely to develop cancer?! Weird. I am looking online and can't find any side effects though. It says CTs are safe. We decided against the cat scan.