FDG Radiotracer: What It Is and Why It Is Used

FDG stands for fluorodeoxyglucose. It is a glucose-like molecule linked to a small radioactive label. After it is given, cells take up FDG in a way that resembles their use of glucose. A PET scanner detects the label and creates an image of where the tracer has collected. FDG is a diagnostic material, not a chemotherapy drug, and it does not treat a tumour.

The tracer follows glucose use rather than identifying cancer on its own. Many active tissues can use more glucose, including some normal organs, healing tissue and areas of inflammation. This is why PET findings need to be interpreted with symptoms, examination and other imaging. The radioactive label also loses activity over time, allowing the body to clear the material after the scan.

FDG is most commonly used as part of a PET-CT scan. The PET component maps tracer activity, while CT supplies detailed information about anatomy. Together, the images may help clinicians assess a known cancer, look for active disease in other body areas, or evaluate how tissue responds during a treatment plan. The exact scan area and preparation depend on the clinical question.

Depending on the question, clinicians may use CT, MRI, ultrasound, an examination, laboratory tests or a tissue sample instead of, or alongside, FDG imaging. These methods answer different questions: an MRI can show soft-tissue detail, while a biopsy can examine cells directly. Your care team selects the approach according to the suspected problem, body region and information already available.

Before the appointment, you may be asked about fasting, medicines and diabetes because blood glucose can affect FDG distribution. During the visit, the tracer is usually given through a vein, followed by a quiet uptake period and the scan itself. A bright area on the image is not automatically cancer; infection, inflammation and normal organ activity can also appear active. The report is interpreted in context by your clinician.

FDG exposure is brief and the material leaves the body through natural clearance, mainly in urine. Drinking fluids and following the imaging department's instructions may support that process. Tell the team if you are pregnant, might be pregnant, breastfeeding or have diabetes, so preparation can be adjusted. Most people return to usual activities after the examination unless their care team gives different instructions.