When your children are sick, it's hard not to want doctors to do everything in their power to cure them. But when it comes to CT scans, less is often more. That's because CT scanners -- which use X-rays to produce richly detailed images of almost any part of the body -- deliver far higher doses of dangerous ionizing radiation than any other commonly used medical imaging device. And children, for a host of reasons, are even more susceptible to the carcinogenicity of ionizing radiation than adults. Scientists have, of course, understood the risks of ionizing radiation for nearly a century.