Patients underestimate CT scan radiation, risks

Will getting two or three CT scans of the abdomen expose you to the same amount of radiation as people who lived near the atomic blast that ravaged Hiroshima in 1945 but survived?
Will they increase your lifetime cancer risk?
If you answered yes to both questions, you're spot on. You're also better informed than many patients at inner-city emergency departments, according to a new survey from Cooper University Hospital in Camden, New Jersey.
Researchers there asked more than 1,100 patients who came in with stomach pain to rate statements similar to the questions above. Half said they had very little faith in the comparison between Hiroshima survivors and patients who had CT scans, rating their agreement at 13 on a scale from 0 to a perfect 100.
The majority of patients also tended to disagree that the scans would up their cancer risk. And three-quarters underestimated the x-ray radiation from a CT scan compared with traditional chest x-rays, which are at least 100 times weaker.
"The point of the paper was not to create mass hysteria," said Dr. Brigitte Baumann, an emergency physician at Cooper, whose findings appear in the Annals of Emergency Medicine.
"The concern is patients who keep coming back to their physicians and get a lot of scans," she told Reuters Health. "But the person who comes in with chest pain coughing up blood" -- a possible sign of blood clots in the lungs -- "a CT scan might save that person's life."
"The whole topic is just a big shade of gray," Baumann said.
In recent decades, the number of Americans who get CT or computed tomography scans has soared, reaching 72 million in 2007.
While the scans help diagnose serious medical problems, some doctors now worry that they may be overused. At a few hundred to a couple thousand dollars per scan, that would mean wasted healthcare dollars -- and as the Hiroshima comparison hints, lost lives.
According to one government study, CT scans done in 2007 alone will cause about 29,000 cancers and kill nearly 15,000 Americans.
From a single patient's perspective, however, the risk seems less daunting: It would take 1000 "average" scans to produce one extra case of cancer in 50-year-olds, the National Cancer Institute's Amy Berrington told Reuters Health in November.
By comparison, about one in three Americans develop some type of cancer during their life, so the extra risk may be a small price to pay if the consequence is better treatment.
The radiation dosage from one scan typically ranges from a few millisieverts -- comparable to the yearly background radiation from natural sources -- to tens of millisieverts.

By Frederik Joelving

NEW YORK | Wed Jan 5, 2011 2:50pm EST

NEW YORK (Reuters Health)