Diagnostic Imaging and Ionizing Radiation

Diagnostic Imaging Techniques

Every day, people undergo medical tests to diagnose diseases and injuries. Some of these tests involve exposure to ionizing radiation. X-rays and CT scans expose patients to radiation externally (from outside the body), while PET and SPECT scans involve administering short-lived radioisotopes to the patients. A gamma camera is then used to take pictures of internal organs and tissues using the radiation emitted by the injected substance. Other tests, such as magnetic resonance imaging (MRI) and ultrasound, do not involve such exposure.

Natural Background Radiation

Natural background radiation refers to the naturally occurring radiation that people are exposed to in everyday life. A dose of ionizing radiation is measured in millisieverts (mSv).

Doses

Health thresholds

  • Dose that could lead to death if it was received all at once and was not medically treated: 5000 mSv
  • Lowest total dose that may cause symptoms of radiation sickness (such as nausea and vomiting) if received within 24 hours: 1,000 mSv
  • Lowest dose at which damage to organs and tissues have been observed following an acute exposure: 100 mSv

Medical sources

  • 1 typical dental x-ray: 0.005 mSv
  • 1 typical chest x-ray 0.1 mSv
  • 1 typical mammogram: 0.42 mSv
  • 1 typical abdominal x-ray 0.7 mSv
  • 1 typical chest CT scan 7 mSv
  • 1 typical full body CT scan 10 mSv
  • Average SPECT or PET procedure 10 mSv (2.6 mSv to 17.7 mSv)

Background sources

  • Eating 1 banana 0.0001 mSv
  • 1 cross-Canada flight (cosmic radiation exposure): 0.02 mSv
  • Annual dose from the Earth’s crust: 0.22 mSv
  • Annual dose from food: 0.29 mSv
  • Annual dose from cosmic rays: 0.32 mSv
  • Annual natural background radiation 1.8 mSv

The Canadian Nuclear Safety Commission regulates the production, transport, uses and disposal of radioisotopes in Canada to protect the health and safety of patients and medical staff.

Exposure to higher doses of ionizing radiation may have harmful long-term health effects. If you’re concerned about a medical procedure that involves radiation, discuss it with your doctor or a qualified radiation technologist.

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Diagnostic Imaging and Ionizing Radiation

The CNSC regulates the production, transport, uses and disposal of radioisotopes in Canada to protect the health and safety of patients and medical staff. Find out more about the radiation doses you’re exposed to in everyday life from medical tests and naturally occurring radiation.