Frequent Questions: Radiation in Medicine

View frequently asked questions and answers related to radiation in medicine by topic.

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General Information

Is it safe for children or pregnant women to have a medical imaging procedure that uses radiation?

Like any medical test, the beneficial information gained from diagnostic imaging procedures should outweigh the risk of having the test performed. Medical imaging is a very powerful and valuable technique that can provide important and even life-saving information.

Radiation exposure is a concern for children and developing fetuses because they are more sensitive to radiation than adults. However, the risks to children or developing fetuses from medical imaging will depend on several factors. These include the type of test being performed, the amount of radiation used, and the region of the body being imaged. Parents and pregnant women should discuss the medical imaging procedure with their physician.

For more information, see the FDA’s X-rays, Pregnancy and You or the FDA’s Pediatric X-ray Imaging webpage.

What are the risks from radiation exposure from medical imaging?

There are benefits and risks associated with any medical procedure, and you should discuss any concerns you have with your doctor. In general, the benefits of needed medical imaging far outweigh the risks. For imaging procedures that use ionizing radiation, such as CT scans, fluoroscopy and conventional x-ray imaging, medical professionals are trained to keep patient doses as low as reasonably achievable (ALARA). Medical professionals are encouraged to optimize doses, which means using the least amount of radiation required to provide adequate image quality or imaging guidance (for fluoroscopy). This optimization or ALARA process minimizes the patient dose of radiation, while still allowing the medical professional to obtain valuable information for treatment decisions. 

There are studies of large populations exposed to radiation that have demonstrated slight increases in cancer risk even at low levels of radiation exposure, particularly in children. To be safe, doctors should presume that even low doses of radiation may cause some slight increase in risk. Optimizing patient doses is particularly important in the case of radiation doses to children. In the case of adults, any individual's cancer risk might be higher or lower depending on a number of factors, including age, lifestyle and heredity.

How is radiation used to diagnose patients?

In 1895, German/Dutch physicist Wilhelm Röntgen discovered x-rays. In one of his experiments, he found that x-rays could pass through the body, producing an image of a skeleton on a photographic screen. Since Rontgen’s discovery over 100 years ago, radiation has been used to create visual images of the inside of the body to diagnose medical conditions. 

Medical professionals use ionizing radiation in specific imaging procedures to help diagnose injuries or illness within the body. The primary goal of medical imaging is to answer a clinical question or guide an intervention. Some examples of the more common medical imaging procedures that utilize radiation include X-rays, computed tomography (CT or CAT scans), and fluoroscopy. 

For more information on the use of radiation in medicine, visit:

Who regulates radiation used in medical procedures?

Depending on the type of radiation and how it is used in medical procedures, different state and federal agencies may play a role in regulation:

  • Individual states regulate the practice of medicine by licensing doctors, including radiologists. - Licensed doctors are permitted to use their experience and discretion in deciding the best procedure for patients, including imaging procedures that use radiation. In the case of radiologists, they may administer exams and determine the amount of radiation necessary to make an image that is useful in treatment decisions. Using only as much radiation dose as is required to achieve adequate image quality should be the goal.
  • The Food and Drug Administration (FDA) regulates medical devices and ensures device safety in all medical settings. FDA also regulates radiation-emitting products and procedures. For more information, see Radiation-Emitting Products: Medical Imaging on FDA.gov
  • The Centers for Disease Control and Prevention (CDC) provides information about medical procedures that use radiation. For more information, see Radiation in Medicine – Medical Imaging Procedures on CDC.gov.
  • The Nuclear Regulatory Commission (NRC) regulates the manufacture and use of radioactive materials in nuclear medicine, radiation therapy and research. For more information, see Nuclear Medicine: What it is – and Isn’t.

The Environmental Protection Agency (EPA) does not directly regulate radiation in medical imaging. However, it does develop and issue general radiation guidance that other federal agencies reference when developing rules and regulations to protect public health. For more information, see Federal Guidance Report No. 14: Radiation Protection Guidance for Diagnostic and Interventional X-Ray Procedures.

How do I make sure that I receive the lowest possible dose of radiation during my medical imaging procedure?

Patients or family members of patients can take a few steps to reduce the dose of radiation during a medical imaging procedure.

  • Discuss the procedure with your physician. How will an x-ray, CT scan, or fluoroscopy procedure help find out what is wrong or determine treatment? Ask if there are other acceptable alternative procedures that might give a lower radiation dose or do not use radiation, but still allow for good assessment or treatment. For example, magnetic resonance imaging (MRI) and ultrasound procedures do not use ionizing radiation.
  • For conventional x-ray imaging, shielding, such as wearing a lead apron, should be used to reduce radiation exposure to other parts of the body.
  • Know your medical imaging history. Keep a list of your imaging records, including dental x-rays. Discuss your diagnostic imaging history with your health care professionals to avoid unnecessary duplication of tests.

X-rays

How much radiation am I exposed to when I get a medical x-ray procedure?

The exact amount of radiation exposure in an x-ray procedure varies depending on the part of the body receiving the x-ray. Some examples of common x-ray procedures and approximate exposures are:

  • Single chest x-ray: 0.02 mSv (2 mrem)
  • Dental x-ray (four bitewings): 0.004 mSv (0.4 mrem)
  • Limbs and joints: 0.06 mSv (6 mrem)
  • Abdomen: 0.7 mSv (70 mrem)
  • Mammogram (four images): 0.13 mSv (13 mrem)

Source: National Council on Radiation Protection & Measurements (NCRP), Report No. 160

Generally, the radiation received during an x-ray is small compared to other radiation sources (e.g., radon in the home). The average annual radiation dose from natural background sources (for comparison) is 3.0 mSv (300 mrem). For more information on radiation sources, see the Radiation Sources and Doses webpage or calculate your radiation dose.

Learn about Radiation Terms and Units like mSv and mrem, which are used to measure radiation dose.

What are x-rays and how are they used in medicine?

X-rays are invisible energy waves that travel through air at the speed of light. X-ray energy is high enough that some radiation passes through objects, such as internal organs, body tissues, and clothing. In an x-ray procedure, the x-ray radiation passes through the body and onto detectors, such as film or an electronic detector linked to a computer. In general, denser objects (such as bones and calcium deposits) absorb more radiation, reducing the amount of radiation that passes through to the detector. Therefore, denser objects leave an image on the detector (that is, they appear lighter) than less dense objects (which appear darker). This is why bones appear white on x-ray images. Radiologists and other specially trained or experienced physicians can read these images to diagnose medical conditions or injuries. 

Is it safe for me to get a medical x-ray?

Generally, the radiation received during a medical x-ray is small compared to other radiation sources. For more information on sources and doses of radiation, visit Radiation Sources and Doses. X-rays can provide life-saving information about medical conditions, so it’s important to discuss the benefits and risks of x-rays with your doctor. 

It’s important to know that the best available science suggests that even low levels of radiation exposure may slightly increase cancer risk. For this reason, it is important to discuss the necessity of an x-ray with your medical professional, particularly for children and pregnant women.

How can I minimize x-ray radiation exposure?

Consumers have an important role in reducing radiation risks from medical x-rays. The U.S. Food and Drug Administration (FDA) recommends several best practices on their website, including:

  • Ask your health care provider how an x-ray will help.
  • Ask if there are other procedures that might be lower risk but still allow for good assessment or treatment.
  • Tell the x-ray technologist in advance if you are, or might be, pregnant.
  • Ask if a protective shield can be used. If you or your children are getting an x-ray, ask whether a lead apron or other shield should be used.
  • Know your x-ray history. Keep a list of your imaging records, including dental x-rays. Show the card to your health care professionals to avoid unnecessary duplication of x-rays of the same body part. Keep a record card for everyone in your family.

For more information, see Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging on FDA.gov

CT/CAT Scans

How much radiation am I exposed to when I have a CT scan?

The total radiation exposure during a CT scan depends on the region of the body under examination. A CT scan may expose the patient to the radiation equivalent of 100-800 chest x-rays. Some examples of CT scans and approximate exposures are:

  • Head CT: 2.0 mSv (200 mrem)
  • Chest CT: 8.0 mSv (800 mrem)
  • Abdomen CT: 10 mSv (1,000 mrem)
  • Pelvis CT: 10 mSv (1,000 mrem)

Source: National Council on Radiation Protection & Measurements (NCRP), Report No. 160

Don’t know what mSv or mrem means? Learn about Radiation Terms and Units.

What is a CT/CAT scan and how is it used?

CT scans (also known as CAT scans or computed axial tomography scans) are advanced x-ray procedures. When a person has a CT scan, they are having many x-rays taken of their body (or part of their body) at nearly the same time. The computer in the CT scanner then combines all of these x-rays to create cross-sectional views and three dimensional images of a patient's internal organs. When a person has a CT scan, they are being exposed to more radiation than when they have a "regular" or conventional x-ray. 

CT scans are useful because they help doctors diagnose problems by creating very clear images of internal organs. The detailed images help identify problems inside the body, like tumors or damage to organs. CT scans can also help doctors prepare for surgery by providing a map of the disease or injury that surgeons can follow when operating.

Is it safe for me to get a CT scan?

CT scans expose patients to a greater amount of radiation than other medical imaging procedures, such as x-rays. Because even low levels of radiation exposure may increase cancer risk, it is important to discuss the necessity of the procedure with your medical professional. Medical imaging can provide life-saving information, so the benefits of a CT scan may outweigh the risks from radiation exposure.

Where can I find more information about CT scans?

For more information on the benefits and risks of CT scans, visit: 

Fluoroscopy

How much radiation am I exposed to when I have a fluoroscopic procedure?

The total radiation exposure depends on the length of the fluoroscopy procedure and the dose of the materials used. An interventional fluoroscopic procedure may expose the patient to the radiation equivalent of 75-3,000 chest x-rays. Examples of fluoroscopic procedures and approximate exposures are:

  • Barium swallow: 1.5 mSv (150 mrem)
  • Barium enema: 7.0 mSv (700 mrem)
  • Coronary angiogram: 4.6-15.8 mSv (460-1,580 mrem)
  • Angioplasty (heart study): 7.5-57 mSv (750-5,700 mrem)

Source: National Council on Radiation Protection & Measurements (NCRP), Report No. 160

Don’t know what mSv or mrem means? Learn about Radiation Terms and Units.

Is it safe for me to have a fluoroscopic procedure?

Fluoroscopic procedures expose patients to a greater amount of radiation than other medical imaging procedures, such as x-rays. It’s important to discuss the necessity of the procedure with your medical professional. Medical imaging can provide life-saving information, so the benefits of the procedure generally far outweigh the risks from radiation exposure.

Where can I find more information about fluoroscopy?

For more information on the benefits and risks of fluoroscopy, visit: 

What is interventional fluoroscopy and how it is used?

Fluoroscopy is like a real-time x-ray movie. It can show the movement of a body part (like the heart) or the course that a medical instrument or dye (contrast agent) takes as it travels through the body. 

Unlike a regular x-ray, during fluoroscopy an x-ray beam is passed continuously through the body. The image is transmitted to a monitor so that doctors can see the body part and its motion in detail.

Fluoroscopy is used in many types of examinations and procedures. Some examples include:

  • Barium x-rays and enemas (to view movement through the GI tract).
  • Catheter insertion (to direct the placement of a catheter during angioplasty or angiography).
  • Blood flow studies (to visualize blood flow to organs).
  • Orthopedic surgery (to help doctors see broken bones and to set the fractures in good alignment).

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Last updated on November 4, 2024