CT Scans and the Cancer Link
Two newly published studies find that commonly used CT scans appear to pose a risk of cancer greater than previously thought.
The studies, published in the Archives of Internal Medicine, support caution and restraint in using CT scans and other procedures that involve radiation.
CT- short for computerized tomography scan - is used to find injuries and tumors. Since the early 1990s, its use has tripled in the U.S. to more than 70 million in 2007, reports the Wall Street Journal.
While the scans use radiation, the exact amount is often uncertain.
One study attempts to find out.
Among more than 1,000 patients, the estimated dose of radiation for a heart scan received at age 40 would result in cancer in 1 in 270 women, and 1 in 600 men. For a CT scan of the head, 1 in 8,100 women, and 1 in 11,080 men would likely develop cancer.
While the scanners deliver radiation from calibrated machines, the dosage varied wildly, according to the study, even within the same hospital. The University of California San Francisco study finds some patients received one-tenth the radiation of others.
Why do the doses differ?
That’s the concern, says author Rebecca Smith-Bindman, of UC San Francisco, a professor of radiology and biomedical imaging, epidemiology and biostatistics.
“They don’t have to be this high” she says to the WSJ, attributing the differences to a lack of standardized settings and how different technicians use the CT scan for different patients.
A higher radiation dose generally generates a clearer picture. The trick is not to use too much radiation.
The second study published Monday, estimates that 29,000 future cancers, particularly those in the abdomen and pelvis, could be related to CT scans received in 2007.
Most impacted are females who receive an abdominal scan at the age of three. She has a 1 in 500 chance of eventually developing cancer.
Mammograms emit a much smaller dose of radiation than CT scans, but the effects are cumulative. These studies echo recent federal guidelines that women should cut back on mammograms, starting later in life and receiving them less frequently.
After Cedars-Sinai in Los Angeles reset a CT scan machine in February of last year, the patients received brain scans received more than eight times the normal dose of radiation, the Los Angeles Times reports.
It came to light when a patient reported he began losing his hair after the scan. More than 200 people had the same exposure and also suffered skin rashes.
A reaction such as hair loss or skin rash should be reported immediately. The Food and Drug Administration (FDA) has issued an alert warning hospitals across the country to check their CT protocols.
Every day more than 19,000 CT scans are performed in the U.S. subjecting each patient to the equivalent of 30 to 442 chest radiographs per scan.
The CT scan is a relatively quick, cheap and painless way to get 3-D pictures into the body to evaluate trauma, belly pain, seizures, chronic headaches, kidney stones especially in the emergency rooms. In kids they are used to diagnose or rule out appendicitis.
Medical radiation now accounts for more than half of the population's total exposure. Previously it was one-sixth, and the top source was the normal background rate in the environment from things like radon in soil and cosmic energy from the sun.
Since previous studies suggest that a third of all diagnostic tests are unnecessary, that means that 20 million adults and more than 1 million children getting CT scans are needlessly being put at risk, according to a published report in 2007 in the New England Journal of Medicine. #