What should you know about a PET scan of the brain?

A glucose-like FDG radiotracer can show how active different areas of brain tissue are. The CT component helps locate structures, while the PET pattern provides functional information. Normal brain activity varies across regions, and medicines, blood sugar, recent seizures, inflammation, and treatment can affect the appearance. An area of altered uptake is not, on its own, proof of a tumour or spread.

In oncology, clinicians may use brain PET findings with MRI, CT, examination results, and the wider cancer history. The scan may help investigate an identified lesion, clarify a question about active disease, or contribute to treatment planning. The intended question should be clear before the appointment because different imaging tests answer different questions.

Follow instructions about fasting, medicines, activity, and blood sugar. Tell the team about diabetes, pregnancy or breastfeeding, seizures, recent illness, and medicines that affect alertness. Rest quietly after the tracer is given, then remain still while images are collected. If you are anxious in enclosed equipment or have trouble lying flat, mention this when arranging the scan. The FDG Radiotracer and PET-CT Scanner pages describe the tracer and equipment in more detail.

Contact the centre if preparation was not possible or if you need an adjustment for mobility, communication, or anxiety. Report a suspected reaction after the tracer. Seek emergency care for a seizure that does not stop, sudden weakness, severe breathing difficulty, or loss of consciousness. Ask when the report will be reviewed, since a brain PET result needs to be placed alongside other neurological and oncology information.

What brain question is this scan addressing? Should I take my usual medicines? Could blood sugar, a seizure, or treatment change the pattern? Is MRI also needed? Who will explain the report and what happens next?