What follows is the AI results of a Google Search [and here is the direct link to that page – there are numerous links to other websites on medical imaging radiation and cancer risk] and then I embed a resource from The American Cancer Society “Understanding Radiation Risk from Imaging Tests”:
AI OverviewMedical imaging tests that use ionizing radiation (such as CT scans and X-rays) carry a very small, cumulative risk of cancer, though the life-saving benefits of an accurate diagnosis almost always outweigh these risks.
How Radiation Causes Risk
- Ionizing radiation: Procedures like CT scans and X-rays use radiation that can damage cellular DNA.
- Natural repair: In most cases, human DNA successfully repairs itself after low-dose exposure.
- Cumulative effect: Unrepaired damage can add up over time with multiple scans, slightly raising long-term cancer risk.
- Dose levels: Standard chest X-rays use tiny doses (about 0.1 mSv), whereas CT scans involve higher doses (typically 2 to 10+ mSv). Read more on Harvard Health.
Vulnerable Groups
- Children: Kids face a higher relative risk per millisievert than adults because they have a longer life expectancy for any delayed effects to appear, and their cells divide rapidly. Recent studies note that cumulative pediatric CT exposure can measurably elevate blood or brain cancer risks, making dose justification critical. [1, 2, 3]
Safe Practices and Alternatives
- Weighing benefits: Doctors use American Cancer Society guidelines to ensure tests are only ordered when medically necessary.
- Lower doses: Modern machines use the lowest effective radiation dose required for a clear image.
Next I review, link to, and embed The American Cancer Society‘s “Understanding Radiation Risk from Imaging Tests”. Last Revised: April 23, 2026.
All that follows is from the above resource.
Low doses of radiation from imaging tests might increase your cancer risk slightly. But it’s important to weigh these risks against the benefits.
This page focuses on radiation risk from imaging tests, including x-rays, CT scans, and PET scans. To learn more about other types of radiation, see Radiation Exposure and Cancer Risk.
How much radiation do I get from imaging tests?
Many imaging tests use less radiation now than in the past, because technology has improved over time.
Studies show radiation exposure from imaging tests varies. The amount of exposure you get depends on:
- The type of imaging test
- The part of your body being tested
- Your size, age, and sex
In many cases, the benefit of having a scan often outweighs the risk. This is especially true for mammograms and screening tests. This means it is important to get screening tests like mammograms, even though you will be exposed to a small amount of radiation.
The risk of having a cancer that goes undetected and untreated is greater than the risk of radiation.
The estimates below are based on an average adult.
To put these numbers into perspective, we are all exposed to some radiation just by being on the planet. Radiation exposure is measured in millisieverts (mSv). The average American is exposed to about 3 mSv of background radiation from natural sources over the course of a year.
X-ray
Chest x-ray: A chest x-ray exposes you to about 0.1 mSv of radiation. This is about the amount you get from natural sources in 10 days.
Standard mammogram: A standard screening mammogram exposes you to 0.28 mSv of radiation. This is about the amount you get from natural sources in just over a month (34 days).
3D mammogram: A 3D screening mammogram exposes you to 0.34 mSv of radiation. This is about the amount you get from natural sources in 42 days.
Lower GI series: A lower GI series using x-rays of the large intestine exposes you to around 6 mSv of radiation. This is about the amount you get from natural sources in 2 years.
Fluoroscopy: This imaging test uses x-rays to make real-time moving images. It exposes you to different amounts of radiation depending on how long it is used.
CT scan
Abdomen and pelvis: A CT scan of the abdomen (belly) and pelvis exposes you to around 7.7 mSv of radiation. This is about the amount you get from natural sources in 2.6 years.
Low-dose CT: This lung cancer screening test exposes you to around 1.5 mSv of radiation. This is about the amount you get from natural sources in 6 months.
PET scan
A PET/CT exposes you to about 22.7 mSv of radiation. This is equal to about 8 years of exposure from natural sources. The radiation exposure from the PET portion of the exam is around 7-8 mSv.
MRI and ultrasound
MRI and ultrasound exams do not expose you to radiation.
How does radiation from imaging tests affect the risk of cancer?
In large doses, radiation can cause serious tissue damage and increase your risk of later developing cancer.
Imaging tests use the lowest dose of ionizing radiation possible. But even with low doses of radiation, there is still concern about whether these tests increase the risk of cancer.
Radiation doses used for screening and diagnostic tests have decreased over the years. Because radiation doses are lower than they used to be, it’s unclear how past research on cancer risk applies to current imaging tests.
Tracking the effect of radiation is also complicated because an individual person’s radiation exposure depends on many factors. This includes the type of test done, the area of the body exposed, and the person’s body size, age, and sex. All of these affect the amount of radiation absorbed by the body.
Current testing guidelines
Health care professionals must follow the as low as reasonably achievable (ALARA) principle.
This means they must use the lowest possible dose of radiation that allows them to get the clearest images they need to diagnose a problem or monitor response to treatment.
Being exposed to a single radiation dose of 50 mSv or a lifetime dose of 100 mSv has not been linked to health risks. These numbers are the upper limits in the guidelines health care professionals follow.
