CT Scans, Other Imaging Tests Becoming More Common
CT Scan Rates Tripled at HMOs in the Last 15 Years, Doubling Radiation Exposure to Patients
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Concerns Over CT Scans continued...
Smith-Bindman says the risk of getting cancer from any one scan appears to be very small. But over time, doses may accumulate, increasing the risk. She says they will be looking at this issue in a future study.
The study also showed that doses of radiation delivered to patients can vary widely for the same test, depending on where it's performed. "Very few facilities know the doses they're using. They don't collect them. They don't look at them, so that's a huge problem," she says.
Though radiologists sometimes use higher doses of radiation to get a clearer image, Smith-Bindman says doses have escalated beyond the range that's needed for image clarity. "The doses are so much higher than they need to be," she says.
And researchers say that they found some evidence that testing was being ordered when it might not be needed.
"We know that in a lot of the cases, the CT really isn't necessary and maybe you can wait. Or if the CT is necessary, then maybe you can just go lower dose," Diana L. Miglioretti, PhD, tells WebMD. She is a senior investigator and biostatistician at the Group Health Research Institute in Seattle.
Miglioretti says the doses of radiation they documented in the study were chilling when viewed in the light of the risks of brain tumors and leukemia documented in the recent Lancet paper.
Assuming typical average doses for CT scans, The Lancet study found that having two to three CT scans of the head before age 15 exposed children to radiation levels that could triple a child's risk of having a brain tumor.
"What we found is that for 10% to 20% of kids, just one head CT scan got them to those levels. So that's really scary," Miglioretti says.
By 2010, 2.5% of patients at HMOs received high annual doses of radiation from CT scans, up from 1.2% in 1996. Similarly, the number of patients who got very high doses of radiation from CT scans jumped from 0.6% to 1.4% in the same period. A high dose was anything between 20 and 50 millisieverts (mSv). A very high dose was over 50 mSv.
The risk for getting higher doses of radiation increased with age. Older patients were scanned more frequently than younger patients.
What Patients Can Do
Researchers say patients shouldn't be shy about asking questions when doctors order a scan, especially if it's a CT scan.
"We need to start getting into these discussions," Smith-Bindman says.
Good things to know before you get a scan include why the test is being ordered, whether or not the test uses radiation, and if it does, how much radiation.
In some cases, she says, patients may have to call the radiologist or imaging clinic to find out about dosing since her study found that many doctors aren't aware of the radiation dose patients are getting.
If you get repeated scans, it's also a good idea to keep track of each test and its associated radiation dose.