PET scans use small amounts of radioactive materials, also called radiotracers, to show differences between healthy tissue and diseased tissue, allowing in vivo imaging of metabolic, physiologic and pathologic processes.
To produce a PET scan, patients have to follow a limited carbohydrate diet for a period of 24 hours before their appointment and fast for 6 hours before the exam. Drinking water is permissible, and drinking 3-4 glasses of water (no juice, tea, coffee) within 2 hours of arriving to the appointment is recommended. Routine medications taken by the patient can be continued unless they are instructed otherwise. Strenuous activity must be avoided for 24 hours before the appointment.
Trace amounts of radiation will be detectable in the patient system for even 24 hours after the scan, so if a patient is travelling over the border after the PET scan, a travel letter needs to be given to the patient. Contact with pregnant women and small children needs to be limited for the same reason.
Diabetics also must take special precautions before a PET scan.