What are the potential side effects of a Positron Emission Tomography (PET) scan, particularly in patients with a history of cancer or other medical conditions?

Side Effects of PET Scans

Radiation Exposure: The Primary Risk

PET scans expose patients to ionizing radiation with a total effective dose of approximately 10 mSv per procedure, consisting of 6-7 mSv from the radiopharmaceutical (typically 18F-FDG) and 2-4 mSv from the low-dose CT component. 1 If a full diagnostic CT is performed rather than a low-dose CT, the total radiation exposure can be considerably higher. 1

Biological Effects of Radiation

• DNA damage and chromosomal aberrations have been documented in lymphocytes following 18F-FDG PET/CT scanning, with chromosome aberration assays showing statistically significant increases post-scanning compared to pre-scanning levels. 2
• The entrance surface dose (ESD) varies by body region, ranging from approximately 32 mGy for head and shoulder regions to 43 mGy for pelvic regions. 2
• Effective doses from the CT component alone can range from 16.40 to 72.18 mSv depending on the protocol used, with dose length products varying from 1093 to 4812 mGy*cm. 2
• Inter-individual variation in induced DNA damage occurs among patients, suggesting that some individuals may be more susceptible to radiation effects than others. 2

Special Population Considerations

Pregnancy and Breastfeeding

• PET/CT procedures should be avoided or postponed in pregnant patients unless the examination is vital for the patient's care. 1
• Interruption of breastfeeding is not necessary after a PET/CT procedure in nursing mothers. 1
• Close contact between the patient and small children should be avoided for several hours after radiopharmaceutical administration due to residual radiation emission from the patient. 1

Pediatric Patients

• Pediatric patients face unique radiation safety concerns due to their increased radiosensitivity and longer life expectancy for potential late effects to manifest. 3
• The combination of two radiation-exposing procedures (PET and CT) creates heightened concern in this population. 3

Contrast Agent Considerations

• When performing PET/CT with intravenous contrast agents, standard CT contrast-related adverse effects may occur, including allergic reactions and nephrotoxicity. 4

Radiation Protection for Personnel and Public

• Healthcare personnel face radiation exposure primarily from handling radiopharmaceuticals (syringe withdrawal, injection, waste handling) and close contact with patients. 1
• The radiation dose to personnel can be limited by applying the inverse-square law—maintaining maximum practical distance from the radiation source substantially decreases absorbed dose. 1
• The energetic nature of positron-emitting radiation requires special radiation protection routines beyond those used for standard diagnostic imaging. 1

Common Pitfalls to Avoid

• Performing a CT scan prior to PET/CT without clinical justification results in unnecessary additional radiation exposure that should be avoided. 1
• Failure to maintain adequate distance from patients after radiopharmaceutical injection increases unnecessary radiation exposure to family members and caregivers. 1
• Not considering cumulative radiation exposure from multiple imaging studies can lead to underestimation of total patient radiation burden. 2

Long-Term Risk Considerations

• The biologically significant radiation dose received during 18F-PET/CT scanning may carry long-term risks, and precautions should be taken to reduce exposure when possible. 2
• Low-dose radiation exposure can induce an adaptive response in cells, potentially requiring higher therapeutic doses for efficacy while simultaneously increasing toxicity to normal cells. 2