Radiation from CT scans needs to be better taught to patients, as their risks are real.

It’s the best way to help curb the rampant ordering of these tests.  Unfortunately, we aren’t doing a very good job.

In a study from the Annals of Emergency Medicine, most patients underestimate their risk from radiation.

When asked to compare the amount of radiation from a CT scan to the amount that Hiroshima survivors were exposed to,

… half [of patients] said they had very little faith in the comparison between Hiroshima survivors and patients who had CT scans, rating their agreement at 13 on a scale from 0 to a perfect 100.

The majority of patients also tended to disagree that the scans would up their cancer risk. And three-quarters underestimated the x-ray radiation from a CT scan compared with traditional chest x-rays, which are at least 100 times weaker.

A government study says that CT scans done in a single year can potentially cause about 29,000 and kill 15,000 Americans. But these macro numbers resonate very little in the setting of an emergency department, or in a primary care office.

Although it’s getting better, there is significant more publicity aimed at a missed diagnosis from not ordering a scan than there is from cancer stemming from CT scan radiation.

And, as the chief investigator of the Annals study notes, “when [patients] go to the emergency department, they’re not really happy if all you do is speak to them; they want more.”

The best we can hope for is to explain to patients the risks and benefits of ordering such scans, and together come up with a shared, informed decision. Of course, our health system isn’t set up for such conversations. There is much more incentive — from a reimbursement, malpractice, and customer service standpoint — to simply order the test.

Until those incentives change, it’s unlikely that studies like these will make a significant impact in physician ordering patterns.

Kevin Pho is an internal medicine physician and on the Board of Contributors at USA Today.  He is founder and editor of KevinMD.com, also on Facebook, Twitter, and LinkedIn.