Computed tomography, or CT scans, were introduced in the 1970s. They allow doctors to see the inner workings of the human body through the use of multiple X-ray images. Their use has grown from 3 million a year in 1980 to more than 80 million today.
CT scans emit a powerful dose of radiation, in some cases equal to about 200 chest X-rays, or the amount most people would be exposed to from natural sources over seven years.
A dose like this can change the makeup of human tissue and create free radicals, molecules that can wreak havoc on human cells. Human bodies can often repair that damage – but not always. When they don’t, the damage can lead to cancer that can take from five to 60 years to develop, with risk that also depends on age and lifestyle.