We fret about airport scanners, power lines, cellphones and even microwaves. It’s true that we get too much radiation. But it’s not from those sources — it’s from too many medical tests.
Americans get the most medical radiation in the world, even more than people in other rich countries. The U.S. accounts for half of the most advanced procedures that use radiation, and the average American’s dose has grown sixfold over the past couple of decades.
Too much radiation raises the risk of cancer. That risk is growing because people in everyday situations are getting imaging tests far too often. Like the New Hampshire teen who was about to get a CT scan to check for kidney stones until a radiologist, Dr. Steven Birnbaum, discovered he had already had 14 of these powerful X-rays for previous episodes. Adding up the total dose, “I was horrified” at the cancer risk it posed, Birnbaum said.
After his own daughter, Molly, was given too many scans after a car accident, Birnbaum took action: He asked the two hospitals where he works to watch for any patients who had had 10 or more CT scans or patients younger than 40 who had had five — dangerous amounts. They found 50 people over a three-year period, including a young woman with 31 abdominal scans.
When other radiologists tell him they have never found such a case, Birnbaum says: “That tells me you haven’t looked.”
Danger is hidden, builds over the yearsOf the many ways Americans are overtested and overtreated, imaging is one of the most common and insidious. CT scans — “super X-rays” that give fast, extremely detailed images — have soared in use over the past decade, often replacing tests that don’t require radiation, such as ultrasound and magnetic resonance imaging.
Radiation is a hidden danger — you don’t feel it when you get it, and damage usually doesn’t show up for years. Taken individually, tests that use radiation pose little risk. Over time, the dose accumulates.
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.
That may soon change. U.S. Food and Drug Administration officials describe steps in the works, including possibly requiring device makers to print the radiation dose on each image so patients and doctors can see how much was given.
The FDA also is pushing industry and doctors to set standard doses for common tests such as CT scans.
“We are considering requirements and guidelines for record-keeping of dose and other technical parameters of the imaging exam,” said Sean Boyd, chief of the FDA’s diagnostic-devices branch. A near-term goal: developing a “radiation medical record” to track doses from cradle to grave.
How much radiation is risky? It’s hard to say. A chest or abdominal CT scan involves 10 to 20 millisieverts (a measure of a dose), versus 0.01 to 0.1 for an ordinary chest X-ray, less than 1 for a mammogram and as little as 0.005 for a dental X-ray. Natural radiation from the sun and soil accounts for about 2 millisieverts a year.
