Radiation Exposure from Routine Tests: What You Don’t Know Can Hurt You

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By Lisa Larkin, MD, FACP, NCMP, IF

Medical providers today have more tools than ever to help with diagnostics. CT scans, X-rays, mammograms – these are all tools that help your provider discover disease or rule out concerns. These tests also have one other thing in common: radiation. Just how much radiation do these tests expose us to, and how much radiation exposure is considered dangerous? When should you agree to a test and when should you ask for alternatives? Understanding more about diagnostic tools and radiation exposure can help patients have an informed dialogue with their provider to make smart decisions.

How much radiation is “safe?” According to the American Cancer Society (ACS), the average American is exposed to about 3 mSv (millisieverts – a measure of radiation exposure) of radiation from natural sources over the course of a year. These sources include things like radon gas from our homes, materials in our environment, even cosmic rays from outer space. This background radiation, as it is called, can vary depending on where we live (i.e., higher altitudes are exposed to more radiation from the atmosphere than lower altitudes.) In general, this amount (3 mSv per year) of exposure is not considered dangerous at these levels.

We do know, however, that larger doses of radiation can increase a person’s risk of developing cancer, and that exposure to radiation is cumulative over a person’s lifetime.

How much radiation do imaging tests expose people to? The amount of radiation a person is exposed to per imaging test depends on a variety of factors, including age, sex, size of person, the protocol selected for the test and the age of the machine itself. Women and children tend to experience increased exposure per the same test than men, which could be related to their overall size.

The ACS states that “a single chest x-ray exposes the patient to about 0.1 mSv. This is about the same amount of radiation people are exposed to naturally over the course of about 10 days. A mammogram exposes a woman to 0.4 mSv, or about the amount a person would expect to get from natural background exposure over 7 weeks.”

But there are other tests that expose patients to higher levels of radiation. Again, according to the ACS,

  • “A lower GI series using x-rays of the large intestine exposes a person to about 8 mSv, or about the amount expected over about 3 years.
  • A CT scanof the abdomen (belly) and pelvis exposes a person to about 10 mSv.
  • A PET/CTexposes you to about 25 mSv of radiation. This is equal to about 8 years of average background radiation exposure.”

Research also has shown us that older machines expose patients to more radiation than newer machines.

Unfortunately, patients are not informed about radiation exposure. Clinicians often don’t think to discuss cumulative radiation effects with patients, and imaging centers are not required to inform patients about the amount of exposure per test or to share the age of their equipment.

What should patients do? First and foremost, stay informed. I often have patients in my practice who worry about the safety of, say, a statin medication, yet don’t bat an eye about getting a (possibly unnecessary) CT scan. Patients should always ask questions and have a meaningful dialogue with their provider about why certain tests are prescribed, and come to an agreement together that the benefit of the test outweighs any potential risks. The ACS also recommends patients keep records of their diagnostic tests throughout their lifetime – to avoid repeated, unnecessary testing, and to monitor the amount of radiation exposure. Sharing this information with all your providers can add to an informed conversation about your overall diagnostic and treatment options.

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