Can radiation from x-rays and computed tomography (CT) scans cause cancer?

The risk of harm from radiation exposure from having diagnostic testing, such as x-rays and computed tomography (CT) scans, is generally considered low. In most cases, the benefits of these tests usually outweigh the risks. However, repeated exposure can have the potential to cause cancer.

Recent estimates are that up to 2 percent of all cancer cases are directly caused by exposure to medical x-ray tests. It is well known that exposure to increasing doses of x-rays, and undergoing repeated x-ray examinations, increases the overall risk of cancer formation. Most radiation experts believe that there is no completely safe level of exposure to x-rays.

A CT scan is an imaging method that uses x-rays to create cross-sectional pictures of the internal body. It is estimated that CT scans of the body may cause at least 2 percent of all new cases of cancer. Most CT scans are performed for very important clinical information. However, some CT scans are still being ordered and performed when they may not be necessary. Talk with your physician to be certain that CT scans are done only when they are medically needed.
Anthony L. Komaroff, MD
Internal Medicine
A 2009 scientific advisory on the topic from the American Heart Association (AHA) offers some perspective. Your risk of developing some type of cancer during your lifetime is 41%, and the risk of dying as a result is 21%. The relative risk of dying of cancer from radiation due to a heart computed tomography (CT) scan is very small in comparison -- an estimated increase of about 0.05% above the 21% background risk. In addition, radiation-induced cancers don't occur until decades after exposure, making the cancer risk even less concerning for older people, who are likely to die from other causes (including heart disease) before developing cancer.

However, a 2010 study in the Journal of the American Medical Association (JAMA) that looked at heart imaging tests on patients at a New York teaching hospital found that many received "alarming and probably unsafe" levels of medical radiation from the tests. About one-third of the tests were done in people without symptoms of heart disease and therefore would not prompt changes in treatment. The findings underscore the AHA's recommendation that tests involving radiation exposure should be ordered only after "thoughtful consideration," including whether an alternative test might do instead. Don't request or agree to any type of medical test unless it will give you and your doctor important information about your health or body. And ask about receiving the lowest dose of radiation possible.
Brian Gelbman, MD
Pulmonary Disease

CT scans and x-rays do involve some radiation, but they are generally considered safe since the radiation dosage for these screenings is low. Watch pulmonologist Brian Gelbman, MD, explain the risks and why frequency of scans should be minimized.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.