Monday, April 4, 2011

How Many CT Scans are Too Many?

Photo credit: Getty Images

"Doctor, do I need a CT scan, or can we do a different test?" 

The following article may help you remember to ask that question.




Japan nuke woes raise radiation awareness

The vastly expanded use of such medical tools as CT scans since the 1980s has led to a sharp spike in a typical American's radiation exposure, studies have shown.

Japan's nuclear plant crisis, while posing no threat here, "will hopefully make us more aware of the very different radiation-related issues that we face in this country," said David Brenner, director of the Center for Radiological Research at Columbia University Medical Center.

The average American is exposed to twice as much radiation annually -- 620 millirems -- as 30 years ago, though that amount remains far below the safety limit set for workers near radioactive material.

Most of that increase has come from an explosion in the use of computerized tomography -- CT scans. In 1980, Americans got about 3 million CT scans; now, more than 70 million a year are performed, according to Brenner.

Too much radiation, which can cause mutations in DNA, has been linked to cancer, including leukemia and thyroid cancer. Experts differ on the degree of health risks associated with medical radiation, but agree caution is warranted.

Brenner stressed "the CT scan is a wonderful tool that has saved countless lives." But he has also estimated 20 percent to 40 percent could be avoided if clinical guidelines are followed. Patient demand and doctors' worries about getting sued for not ordering tests are helping drive the increase.

"There is a very strong body of evidence that too many CT scans are being done in this country and many should not be done at all or should be replaced by something else," Brenner said.

A CT scan machine is essentially a computerized X-ray device that rotates, making three-dimensional cross-sectional images, or slices, of organs and body parts, and providing greater detail than conventional X-rays. Instead of a single beam, multiple X-rays are sent simultaneously from different angles, generally boosting the overall dosage.

The U.S. leads the world in CT scans per capita -- twice the average of other developed nations, according to the Organization for Economic Co-operation and Development. The American College of Radiology acknowledges their widespread use has led to more radiation exposure and has repeatedly said that unless the medical benefit outweighs the risk, such tests should not be performed.

Big dose from CT scans
About half of the average American's radiation comes from our natural environment, depending on where you live, according to the Nuclear Regulatory Commission. Residents of Long Island, near sea level, get less cosmic radiation than those in mile-high Denver, for instance.

The remaining average annual exposure is attributed to the increase in use of medical devices, especially CT scans.

A single heart CT scan delivers about 2,000 millirems. A chest scan averages 700 millirems, 70 times as much as a chest X-ray. A dental X-ray is only about 0.5 millirems.

International standards allow nuclear materials workers to be exposed to up to 5,000 millirems annually.

The NRC estimates that 50 percent of a population would die within 30 days after receiving a dose of between 350,000 to 500,000 millirems to the whole body over a period of a few minutes to a few hours.

Doses of less than 10,000 millirems spread out over years don't cause an immediate problem to body organs. The effects of this level of radiation, if any, occur at the cell level and would not be observed for 5 to 20 years after exposure, the NRC said.

A National Cancer Institute researcher, Amy Berrington de Gonzalez, and others calculated in a 2009 study in the Archives of Internal Medicine that CT scans performed in the U.S. in 2007 could lead to 29,000 future cases of cancer and 14,500 deaths.

The risk to any individual is likely small, the researchers said. But with CT scans so heavily used, even small risks "could translate in a considerable number of future cancers," especially in children.
The American College of Radiology has questioned the findings, but said it was still safer "to act as if low doses of radiation may cause harm."

Researchers also found a wide variation of radiation doses between CT scans. In the same Archives issue, Berrington de Gonzalez and others looked at scans at four San Francisco facilities and discovered routine chest CT scans emitted anywhere from 200 to 2,400 millirems.

The researchers blamed the lack of a national standard. Except for mammography facilities, the federal government has not regulated the use of X-ray devices.

Change coming in 2012
That will change next year when any nonhospital facility that offers CT scans and receives Medicare must be accredited by the American College of Radiology. That process includes ensuring doctors and technicians have the needed training and equipment works properly. ACR has called for hospitals that bill Medicare for medical imaging and radiation oncology to be accredited too.

In New York, the state health department requires facilities to ensure radiological imaging machines are properly used and deliver the right doses. It recommends, but doesn't require, accreditation.
ACR has accredited 404 CT facilities in New York. Neither ACR nor the health department knew the number of unaccredited facilities.

The U.S. Food and Drug Administration last year launched an effort to work with manufacturers and doctors on safeguards to ensure CT scans don't deliver more radiation than necessary.

Radiology groups like ACR have developed awareness campaigns to alert other medical professionals who order tests of the need to reduce unnecessary radiation exposure, especially duplicative scans.
Doctors must learn to ask, "Do I need this CT scan or can I do something else?" said Bill Robeson, radiation safety officer for the North Shore-LIJ Health System.

In the meantime, few patients -- or their doctors -- keep track of cumulative lifetime exposure to medical radiation, experts said. Keeping a record is a good idea.Dr. John Pippin, a Dallas cardiologist and senior medical and research adviser for Physicians Committee for Responsible Medicine, offers this advice: "The best question to ask [your doctor] is, 'What's the risk of having this done and the actual risk I would have the disease you're looking for?' "

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