PET scan - Risks of PET scans

During a positron emission tomography (PET) scan, your body's tissue will be exposed to radiation.

Any exposure to radiation carries a risk of damaging the body's tissues and possibly triggering cancer at a later date. However, the risk is very small.

Radiation is measured in units known as millisieverts, or mSv for short. A standard PET scan would expose you to about 8mSv, which is the same amount of radiation that you are exposed to from natural sources of radiation, such as the sun, over the course of three years.

A combined PET-CT scan would expose you to between 15-25mSv. The recommended annual limit that someone who works with radiation should be exposed to over the course of a year is 20mSv.

Most experts believe that the risk of cancer developing only becomes significant in people who are exposed to 100mSv or more.

However, as a precaution a PET scan is not recommended for pregnant or breastfeeding women unless the benefits of the scan clearly outweigh any risks to the baby. Close contact with pregnant women, babies or young children should be avoided for a few hours after having a PET scan.