What should you know about PET-CT scan images?

The PET part displays where the injected FDG radiotracer collects because cells are using glucose. The CT part shows the shape and position of organs, bones, blood vessels and other structures. Software combines these views so a bright area can be matched with its location in the body.

A bright region is not a diagnosis by itself. Infection, inflammation, healing tissue and some normal organs can also take up FDG. Some cancers show little tracer activity, and very small areas may be difficult to resolve. A specialist reads the complete study alongside your symptoms, examination and other results. The written report matters as much as the pictures.

Keep the report and ask which findings are definite, which are uncertain and whether comparison with an earlier scan changes the interpretation. Ask whether a tissue sample, MRI, ultrasound or follow-up scan is needed before treatment decisions are made. Preparation details, such as fasting and managing blood glucose, can affect image quality for a future examination.

You can learn about the scan in [PET-CT Scan](/treatments/diagnostics-and-staging/pet-ct-scan/) and the scanner in [PET-CT Scanner](/technology/pet-ct-scanner/). The tracer is described in [FDG Radiotracer](/materials/fdg-radiotracer/).

Contact the imaging or oncology team promptly if you develop breathing trouble, facial or throat swelling, widespread rash, faintness or severe weakness after the appointment. These symptoms need timely assessment, although reactions are uncommon. A scan finding alone is not an emergency; follow the review plan given by your clinician.

Which areas on the images need attention, and what does the CT portion show there? Could inflammation or recent treatment explain the activity? Do I need another test or a biopsy? When will the report be reviewed with me?