Half of all medical procedures that involve radiation happen in the U.S. The average American is on the receiving end of six times the amount of radiation they would have been exposed to a few decades ago.
Higher radiation dose means higher risk of getting cancer.
CT scans have become more popular in the last ten years, and are often substituted for other tests that don't involve radiation. An individual test may not offer a high radiation dose, but there is a cumulative effect in the amount of radiation when tests are used repeatedly.
"Doctors don't keep track of radiation given their patients — they order a test, not a dose. Except for mammograms, there are no federal rules on radiation dose. Children and young women, who are most vulnerable to radiation harm, sometimes get too much at busy imaging centers that don't adjust doses for each patient's size."
U.S. heart attack patients can get an amount of radiation equal to 850 chest x-rays in just a few days hospital stay. The Food and Drug Administration is looking into ways to bring some regulation onto the scene.