Does a PET Scan Have Risks?

A positron emission tomography scan is considered risk-free for most patients, except pregnant women, breastfeeding mothers and infants, notes MedlinePlus. Since infants and unborn babies are in the early stages of biological development, they have a higher vulnerability to radiation symptoms than older children and adults.

PET scans are imaging tests classified as "nuclear medicine," or procedures that require exposure to radioactive material, according to Johns Hopkins Medicine. During the procedure, a radiologist releases a tracer drug, known as a radionuclide, into the patient's bloodstream. The radionuclide contains such a minimal amount of radiation that it usually doesn't have any harmful affect on the body. However, radiation can contaminate breast milk and be passed from mother to child. Patients with diabetic needs may have to take an insulin dosage earlier than usual because meals are not permitted for several hours before the procedure.

Radionuclides are intended to break down, so radiation typically clears out of the system in two to 10 hours, states MedlinePlus. The tracer may trigger an allergic reaction in rare cases, but the patient usually experiences minor side effects, such as swelling or soreness where the drug was injected. PET scans aren't medically risky for patients with claustrophobia, but these patients may experience panic, anxiety or discomfort while inside the tunnel-like chamber of the PET machine.