Contrast used in a PET scan

These substances have different jobs. The tracer shows patterns of activity in tissues; CT contrast, when included, helps define anatomy. Your appointment instructions should say what you will receive and how to prepare.

FDG is a glucose-like radiotracer injected before imaging. Tissues take it up to different degrees, and the PET-CT scanner detects the signal to map metabolic activity. Areas of increased uptake are not automatically cancer; inflammation, infection and normal organ activity can also affect the pattern.

The linked CT images show where that activity sits in the body. Some examinations use a low-dose CT for positioning and anatomical reference, while others include diagnostic CT contrast. The scan team interprets PET and CT findings together with your medical history and other tests.

Follow the centre's directions about fasting, drinking water, exercise and medicines because blood glucose and recent muscle activity can alter FDG distribution. Tell staff if you have diabetes, are pregnant or may be pregnant, are breastfeeding, or have difficulty lying still.

Also report kidney problems or a previous reaction to imaging contrast in case CT contrast is planned. After the tracer injection, you will rest quietly during its uptake period. Limit close contact with pregnant people and young children only for the period specified by your imaging team.

Tell staff straight away about pain or swelling at the injection site, hives, facial swelling, wheezing, throat tightness, dizziness or breathing difficulty. Severe reactions are managed as emergencies wherever they occur.

Once home, seek emergency help for collapse, breathing trouble, or swelling of the lips, tongue or face. Contact the imaging service for a spreading rash or worsening injection-site pain or swelling, and explain which substances you received if known.

Ask which radiotracer is planned, whether the CT portion will use injected or oral contrast, how diabetes medicines should be handled, how long preparation and imaging may take, and what contact precautions apply afterward.