A healthy living blog from Marshfield Clinic Health System

Medical imaging tests and radiation: What you should know

Illustration of man in a MRI machine - Are medical imaging tests safe?

Talk with your care team if you have questions about medical imaging tests and radiation exposure.

Certain medical imaging tests expose us to radiation. Overexposure to radiation can be a cause of cancer, so it’s good to be aware when you have a medical test that exposes you.

Marshfield Clinic Health System radiation oncologist Dr. Patricia Lillis said we are all exposed to radiation every day whether or not you have a medical imaging test done. Radiation from the sun and radon, a gas, are natural sources of exposure we all experience. Radiation exposure is slightly greater for people who live at higher altitudes.

What tests expose you to radiation?

“In medical imaging tests, you are exposed to a variable amount of radiation depending on the test,” Lillis said. “Each study requires a different amount of radiation to produce the desired image.”

Lillis said MRIs and ultrasounds do not use radiation, while X-rays, CT scans and nuclear imaging tests do. Harvard Medical School published a chart showing the average dose of radiation exposure in multiple different tests.

The unit of measurement for radiation is a millisievert. The average person is exposed to about 3 millisieverts of radiation each year.

Body part and body type matter

Lillis said different areas of the body are more or less sensitive to radiation. The hands and skin, for instance, can tolerate more than the eyes or sexual organs. She added that your body composition also factors into your exposure. More radiation is required to produce an image for larger individuals.

Weigh the risk

With multiple scans, your level of radiation exposure can add up.

“You have to balance the potential risk of exposure against not finding out whatever potentially bad disease you may have,” she said. “It may be worth the risk. It’s a risk-benefit ratio.”

Lillis said it is important providers and patients talk through options and ensure unnecessary tests are not ordered. If you have questions about an imaging test you may need, discuss it with your care team.

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