Hospitals Monitor Radiation Exposure from Medical Tests
Tuesday, October 6, 2009
Since August, patients who undergo CT scans at the National Institutes of Health Clinical Center have gotten a little something extra: a record of the amount of radiation they were exposed to during the test.
The NIH center joins a small number of hospitals and outpatient imaging centers across the United States that automatically transmit radiation data to a patient's record whenever certain scans are done. Beginning next year, at Brigham and Women's Hospital in Boston, all scans performed at the hospital and those done in the past 22 years will be in a patient's record. Each time a new scan is ordered, the file will spit out the number of past tests and the estimated risk of cancer for the patient.
A study done at New York's Columbia University Medical Center, published in 2007 in the New England Journal of Medicine, estimated that as many as 2 percent of cancer cases in the United States could be linked to radiation from CT, or computed tomography, scans, which emit more radiation than many other procedures.
"We don't have a definitive radiation level that we know to be dangerous," says James Jelinek, head of radiology at Washington Hospital Center, "but we do know theoretically that large doses of radiation may slightly increase the risk of cancer."
Something else researchers know is how dramatically the number of CT scans performed in the United States has increased, from 3 million in 1980 to 62 million in 2006. Researchers at Emory University reported in August that examination of three years' worth of insurance records of nearly 1 million adults showed that 68 percent had at least one CT scan in that period.
Now that more children are also getting CT scans, concerns are being raised because young people are considerably more sensitive to radiation than adults and because early exposure makes them more likely to accumulate high levels of radiation in their lifetime. One reason doctors request CT scans on children is that they can obviate the need for sedation, often required for invasive tests. Another reason is speed. For example, said Jelinek, appendicitis used to be diagnosed by assessing abdominal pain and waiting, often for hours, to see if it progressed, during which time an appendix could burst. "Now," he said, "we can do a CT scan of the abdomen and see, often within 15 minutes, whether the cause is appendicitis."
The time when a significant number of hospitals automatically send imaging test data to a patient's record is probably years away, says James H. Thrall, chair of the American College of Radiology and head of the radiology department at Massachusetts General Hospital. Meanwhile, concerned patients can keep track of the information for themselves and their families. The Alliance for Radiation Safety in Pediatric Imaging has a downloadable card on its Web site (http:/
The specific amount of radiation emitted isn't tracked on the card, Farley says, because the emission can vary from scanner to scanner and because a patient's size can affect the amount of radiation absorbed. But physicians can get "a general idea of how much radiation a patient received just by seeing the type of test," says Robert Zeman, head of radiology at the George Washington University Hospital. Zeman suggests that patients have the physician or technician fill out the card for them to be sure all available information, such as whether a dye was used, is recorded.
The average American receives an effective annual dose of about 300 millirems, a unit of radiation measurement, from naturally occurring materials. About two-thirds of it comes from radon gas in soil, rock and water; some comes from cosmic radiation from outer space.
Ultrasound and MRI tests emit no radiation; most X-rays, including dental X-rays, expose people to less than 1 millirem. A mammogram emits about 13 millirems. CT scans give off much more radiation: Abdominal scans emit about 1,000 milllirems and and scans of coronary arteries can be double that.
At least a third of the 1 million patients in the Emory study had received radiation doses equivalent to 2,000 millirems. Exposure to 300 to 2,000 millirems is considered moderate; more than 2,000 millirems is referred to as high.
Repeated medical tests can make even small levels add up, which is why keeping a record can be valuable, Thrall says. For example, if you needed a tooth pulled, an oral surgeon could check your record to see how recently dental X-rays were done and maybe eliminate the need for another set.
Jelinek advises consumers to record and share their imaging test information with family members, so they can remind each other to take the record to medical appointments or grab it if someone is rushed to the emergency room. Because CT scans can deliver information so quickly, their use has especially increased in the ER. But if you've had a number of scans previously, you or a family member may want to review the list with the attending physician to see if a scan is the best option -- "though if the doctor says your life depends on the quick results the scan can provide, opt for the scan," said Zeman.