What is a PET-CT scan, and when does it help in cancer care?
PET-CT combines information about tissue activity from a radioactive tracer with CT anatomy. It can help stage selected cancers or assess treatment response. It is not a universal screening test, and increased uptake does not always mean cancer.
Details
Why the scan is not a diagnosis by itself
Inflammation or infection can increase tracer uptake, while small or poorly tracer-avid tumours may be missed. Images must be interpreted alongside clinical information and other tests. A biopsy may still be needed.
Preparation depends on the tracer
Follow the centre’s instructions about fasting, exercise, glucose and medicines. Tell staff about diabetes, possible pregnancy, breastfeeding or difficulty lying still. Do not guess how long to stop diabetes medicines or breastfeeding; instructions depend on the tracer and appointment.
After the scan
Obtain advice about fluids and any temporary precautions around children or pregnant people. Discuss the result with the requesting clinician and ask how it changes care. Repeated imaging without a clear clinical question can add radiation and unnecessary follow-up tests.
Related reading: What is the difference between cancer stage and grade?.