What should you know about PET scan used for cancer?

The FDG tracer follows glucose activity in the body, while the CT portion shows where that activity is located. Doctors may use the combined images to investigate a suspected cancer, look for disease in other parts of the body, help choose a biopsy site, plan treatment, or assess how a known cancer is responding.

Increased FDG activity is not specific to cancer: infection, inflammation, healing, and some normal tissues can also appear active. A PET-CT does not replace tissue sampling when a biopsy is needed. The report is interpreted with your history, examination, blood tests, and scans such as ultrasound, MRI, or CT.

Use the preparation instructions from the imaging centre. They may include fasting, avoiding strenuous activity, drinking water, and discussing medicines that affect blood sugar. Tell staff about diabetes, pregnancy or possible pregnancy, recent illness, and any difficulty lying flat. After the tracer is given, rest quietly and keep warm while it distributes before the images are taken.

Report breathing difficulty, swelling of the face or throat, severe dizziness, or a rapidly worsening reaction during the visit immediately. Afterward, seek urgent care for those symptoms or for severe weakness, persistent vomiting, or a painful injection-site reaction. If the scan has raised concerns, arrange the recommended follow-up rather than interpreting isolated findings alone.

Ask what the scan is intended to answer, whether a biopsy or another scan is also needed, how preparation affects your medicines, and when the report will be reviewed with you.