Why is FDG radiotracer used in a PET-CT scan?

FDG stands for fluorodeoxyglucose, a glucose-like substance carrying a small radioactive label. After it is given, tissues that use more glucose may collect more FDG. The PET part detects that signal and creates a map of activity; the CT part shows the location and anatomy of the same area.

In oncology, this combination can help clinicians look for active disease, assess how far it may extend, and compare findings over time. Increased FDG uptake is not specific to cancer: infection, inflammation, healing tissue, and some normal organs can also appear active. The scan therefore needs to be interpreted with symptoms, examination, and other test results.

Follow the imaging team's instructions about eating, drinking, medicines, and blood glucose before the appointment. Tell them about diabetes, pregnancy or possible pregnancy, breastfeeding, recent illness, and difficulty staying still. After the injection, you usually rest quietly while the tracer distributes, then lie still during the scan. The appointment may take time because movement can reduce image quality.

Contact the imaging service promptly if you develop troublesome symptoms after the visit, or if you have diabetes and your glucose becomes difficult to manage. Seek urgent help for breathing difficulty, facial or throat swelling, fainting, or sudden severe illness. These reactions are uncommon, but they need immediate assessment.

Ask what the scan is intended to answer, whether your blood glucose or medicines need special planning, and when results will be reviewed. You can also ask how inflammation or recent treatment might affect FDG uptake and whether another test is needed to clarify an uncertain area.