Radiation from health scans causes concern
Increasing use stirs cancer fears
By
LAURA GEGGEL
P-I REPORTER
(Editor's note: This story has been changed since it was first published. The previous version incorrectly stated that Magnetic Resonance Imaging uses radiation.)
Cheryl Smith's cancer went into remission after her mastectomy two years ago, but she travels from Port Angeles to Seattle annually so doctors at Virginia Mason Medical Center can scan her to check for a relapse.
Last month, she had her second CT scan, four years after she was diagnosed with late-stage breast cancer. She said the radiation exposure from the scan is hardly a major concern for her.
"I think about it once in a while," said Smith, 58, but she noted that people flying around the world regularly receive relatively high levels of natural radiation 40,000 feet closer to the sun.
But Smith's CT scan subjected her to nearly 300 times the radiation she would have received on a roundtrip, coast-to-coast flight, according to data from the American College of Radiology.
Americans are being exposed by scans to record amounts of ionizing radiation, the most energetic and potentially hazardous form of radiation. Some researchers are concerned not only that the procedures are being overused, but also that patients may have no idea how much radiation they are receiving. Some physicians are worried that increased radiation exposure could lead to higher cancer rates.
"A CT scan of the chest will give you about the same radiation dose to the breast tissue as 10 to 20 mammograms," said Dr. Fred Mettler Jr., professor emeritus of radiology at the University of New Mexico and representative to the United Nations for nuclear radiation effects.
"Most women don't have a clue," he said. "Most people would get up and leave if they knew that."
Mettler is the principal investigator for the National Council on Radiation Protection's report on sources and magnitude of radiation exposure in the United States. Funded by the Nuclear Regulatory Commission and the Environmental Protection Agency, the report is expected to be published early next year.
Most radiation exposure previously came from natural background radiation. While advances in radiology have radically transformed medical practice and allow pinpoint diagnostics and treatment, they also have meant that more people are getting more radiation.
Clinical imaging exams in the United States are largely responsible for the per capita dose of ionizing radiation increasing almost 600 percent from 1980 to 2006, concludes the new report.
Though CT scans make up only 12 percent of all medical radiation procedures, they deliver 46 percent of the total dose of radiation exposure in the United States, Mettler said.
The report found that the number of CT scans jumped from 3 million in 1980 to 62 million in 2006. Mettler called the increase "staggering." He said that amounts to about one CT scan a year for every five people in the United States.
No one is saying that CT scans should be eliminated. However, researchers such as Mettler believe the Food and Drug Administration should take a more active role, and that patients need to be better informed about radiation doses.
Despite their high radiation, diagnostic radiation machines are not regulated by the FDA. Only mammogram facilities must be periodically accredited by the American College of Radiology to qualify for Medicare funding.
Other countries do have regulations. The United Kingdom requires hospitals to carry out periodic dose audits to show that the mean radiation doses for the entire hospital do not exceed national reference levels.
"The Europeans are ahead of us in this area in measuring dose and making people more aware of what the risks are," said Dr. Brent Stewart, a professor of radiology at the University of Washington. "The American College of Radiation is taking a very progressive stance in implementing these ideas of dose consciousness. We need to do more to raise the consciousness of referring physicians."
The radiology department at Virginia Mason employs precautions when it comes to CT scans, checking if the patient has had a CT scan at another hospital within 24 hours and sometimes questioning the size of the requested scan. Radiology technologists also give women 70 and younger a breast shield that deflects a percentage of low-dose radiation known to linger in breast tissue.
"We generally don't use CT scans unless there is a life-threatening condition," said Giao Nguyen, an emergency room doctor at Virginia Mason.
"When you image a patient, you're trying to answer a question," said Dr. Marie Lee, a radiologist at Virginia Mason. "You want to be sure that the question you're asking can be answered by the radiation."
Lee compared the images produced by a CT scan as akin to looking at a detailed anatomy textbook, but cautioned that radiation in larger amounts can have complications that may lead to cancer.
Stewart said that the University of Washington Medical Center and Harborview Medical Center are trying to implement an electronic order entry system that would allow physicians access to radiology guidelines and show how frequently patients are receiving radiation.
Stewart offered patients some advice.
"The patient, as a good consumer, ought to know as much as possible and ask as many questions as they need to be satisfied," he said.
Like driving on the highway, he said, using medical radiation involves risk.
Radiologists are still studying the correlations between medical radiation and cancer rates. A 2004 study in The Lancet surveying data from 1991 to 1996 suggested that medical radiation accounts for only 1 percent of American cancer cases, but a May 2007 report from the American College of Radiation stated that most radiation-induced cancers can take 10 to 20 years to occur.
Stewart said there is still some debate about the carcinogenic effect of medical radiation.
"At this point, we don't know for certain whether small doses of radiation like chest X-rays are injurious to a person overall," Stewart said.
But Mettler wants more safety precautions in place. Radiation doses for the same procedure can vary in the hands of different practitioners by as much as a factor of 10, reports the FDA. He would like to see the FDA actively involved in pressuring manufacturers to use lower radiation doses that still produce good images.
"There's a huge amount of pressure to order these things, but people just don't know how much radiation there is," he said.
SCANS
CT, or Computed Tomography, scans take a series of X-ray slices of an area of concern. A computer combines the slices to form a multidimensional view. Dyes, each highlighting separate soft tissues in the body, such as blood vessels or the colon, show up in shades of gray on the resulting CT image.
Carrie Richardson, a radiation technologist at Virginia Mason Medical Center, said the denser areas are grayer: "The overall density of a healthy organ should be all the same tone." If an organ appears to be different hues, physicians may order a biopsy.
Magnetic Resonance Imaging also captures images of patients using non-ionizing radio waves. But MRIs require more time than CT scans, provide less detail and cannot portray motion as well.
Cumulative Radiation Concern
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