High-tech screening tests: Too much radiation?


When President Obama went in for a recent check-up, he took the fast track. Instead of a traditional colonoscopy performed with an endocscope, he had a virtual colonoscopy done with a CT-scan. It is quicker, less invasive, and meant the president would not have to undergo anesthesia. But there was a trade-off.

"Definitely the convenience is at the cost of radiation, and that's the problem," says Dr. Rita Redberg, director of cardiology at the University of California at San Francisco. She is also among a vocal group of medical experts who argue that Americans are receiving too much radiation; partially, from a new wave of high-tech screening tests such as the coronary-calcium scan, which the president also received on his heart, and which also employs a powerful CT-scanner.

"So when you go through one of these virtual colonoscopies, or coronary-calcium scans, you don't realize you've just had 50 to 100 to 200 chest x-rays," says Redberg.

Redberg was concerned enough to write an online editorial about the president's check-up and the example it set.

Her concern centers around the increased frequency of radiological screening over the past decade. Last year alone, an estimated 70 million Americans underwent an exam that involved at least some level of radiation.

"The problem is that there's an increased cancer risk even from little amounts of radiation that we don't feel," says Redberg. "So a CT-scan here and a CT-scan there, and they start to add up and you've increased your chance of getting cancer."

Still, with hearings scheduled for next week in Washington, D.C., other experts argue that average Americans need a better understanding of the benefits and relative risks of the powerful imaging tests.

Dr. Fergus Coakley is a professor of radiology at UCSF. He says a good way to measure the tests are against the normal background radiation we absorb from the sun and earth's atmosphere.

"The typical CT-scan might give you a dose of 10 millisieverts and that's the same amount of radiation you would just get from background radiation over two or three years," says Coakley. "I think that's a better comparison than looking at the number of chest x-rays."

He agrees that dosage and frequency of testing should be closely monitored, but argues that the decisions on how and when to use the powerful technology should be left to doctors.

"I personally don't like the idea of a big government top-down answer telling us how much radiation to use in a given study," he says.

Whatever the outcome, hospitals across the country are likely to closely examine their policies regarding screenings.

"How many of them are necessary? We don't know. But certainly we're doing more scans and we're doing more scans with radiation," says Redberg.

The FDA hearings we mentioned will be held on Tuesday and Wednesday of next week. They will focus on three areas – CT-scans, nuclear medicine studies, and fluoroscopy.

Written and produced by Tim Didion.

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