The short answer
Some imaging tests, like CT scans and x-rays, use ionizing radiation, which carries a small cancer risk. For most people the benefit of a needed scan far outweighs the risk. MRI and ultrasound use no ionizing radiation.
NCI says x-rays, CT scans and PET scans can cause cell damage that leads to cancer, but the risk from these tests is very small.
People are mainly exposed by undergoing x-ray and CT imaging tests.
NCI says the benefit of these tests is almost always greater than the risk.
A carcinogen classification describes hazard — whether something can cause cancer — not your personal risk at a given exposure.
Choose how you want to read this
The whole article, with every detail and caution.
The simple version
Medical imaging such as x-rays and CT scans uses small amounts of ionizing radiation to see inside the body. That radiation carries a very small added cancer risk. Still, a scan your doctor recommends usually brings benefits that far outweigh the risk. Some tests use no ionizing radiation at all, including MRI and ultrasound.
What medical imaging radiation is
X-rays and CT scans pass ionizing radiation through the body to make images. MRI and ultrasound do not use ionizing radiation.
How people are exposed
Exposure comes almost entirely from medical tests:
- CT scans, x-rays, and PET scans.
- Exposure from many repeated scans adds up, which is why the FDA suggests keeping a record of your imaging.
- The FDA says children are more sensitive to radiation and often have multiple scans, so special care applies to pediatric CT.
The cancer connection
The National Cancer Institute says that chest x-rays, CT scans and PET scans can cause cell damage that leads to cancer. It also says the risks from these procedures are very small, and the benefit from having them is almost always greater than the risks. The FDA estimates that a CT scan at 10 millisieverts may add about a 1 in 2,000 chance of fatal cancer, compared with a natural cancer risk of about 1 in 5 in the U.S.
Hazard is not the same as risk
Calling imaging radiation a carcinogen speaks to hazard. Hazard is whether something can cause cancer under some conditions. That is not the same as your personal risk. Your risk depends on how much you are exposed to, for how long, and other factors. A hazard label says a thing can cause cancer. It does not say how likely that is for you.
How to lower your exposure
- Ask if a scan is needed, and whether MRI or ultrasound could work instead.
- For a child, ask whether the scan is needed and whether another test could be used.
- Keep a record of past imaging so tests are not repeated for no reason.
- Do not skip scans your doctor considers important out of fear.
To see where medical imaging radiation sits among all the things that affect cancer risk, read our overview of cancer prevention and what raises cancer risk.
The bottom line
Radiation from imaging can cause cell damage that leads to cancer. The National Cancer Institute says the cancer risk from these tests is very small, and the benefit is almost always greater than the risk. The useful questions are whether a scan is needed and whether a test without radiation would work.
Common questions
Does medical imaging radiation cause cancer?
It can. NCI says chest x-rays, CT scans and PET scans can cause cell damage that leads to cancer, but the risk from these tests is very small and the benefit is almost always greater than the risk.
How are people exposed to medical imaging radiation?
Most exposure happens by undergoing x-ray and CT imaging tests.
Which cancers are linked to medical imaging radiation?
Radiation from imaging can cause cell damage that leads to cancer. For a medically needed scan, NCI says the risk is very small and the benefit is almost always greater.
How can I reduce my exposure to medical imaging radiation?
Ask your doctor whether the test is necessary, and about its risks and benefits. Keep a record of your imaging, and ask whether a test without ionizing radiation, such as MRI or ultrasound, could work.
Does a carcinogen label mean I will get cancer?
No. A classification is about hazard — whether medical imaging radiation can cause cancer under some conditions — not a prediction that any one exposed person will develop cancer. Your actual risk depends on the amount and length of exposure and other factors.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Talk with a trained specialist or navigator
Cancer Explained provides educational guidance, but does not replace trained specialists, social workers, or your medical team.
Talk to a trained cancer information specialist
Free, confidential assistance from NCI Cancer Information Service via phone, chat, or email.
Contact your oncology team
Locate after-hours contact numbers, portal messages, or urgent triage phone lines.
Find a patient navigator
Get one-on-one help with appointments, logistics, translation, and care coordination.
Find a genetic counselor
Discuss inherited mutation risk, family history, and genetic testing options.
Find an oncology social worker
Access emotional counseling, family support groups, and mental health resources.
Find a financial navigator
Locate copay assistance foundations, grant programs, and lodging/travel support.
Find a clinical-trial specialist
Search matching studies and speak with NCI trial information specialists.
Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Last updated: 2026-10-16Next planned review: 2028-07-05
Review details and limits
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status — Source checked. This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
General education — varies by person. Answers genuinely differ between people. This page explains what commonly varies and points you to your care team for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
Words to know
Tap any term to see what it means.
Knowledge check
0 of 2 answered
This self-assessment checks understanding of educational content only. It is not medical advice.
How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
Read more about our editorial process, our use of AI, and our corrections policy.
Spotted a problem? Report an error — a factual mistake, broken or outdated source, confusing wording, or anything that seems unsafe. Please do not include names, medical record numbers, dates of birth, addresses, or other identifying medical information in your report.
After using this page, do you understand what to do next?
Anonymous — we only record the answer, never who gave it.