- Fluorodeoxyglucose (FDG) is a radiolabeled glucose analog widely used in positron emission tomography (PET) imaging to visualize and measure tissue metabolic activity, particularly glucose metabolism. Its full chemical name is 2-deoxy-2-[¹⁸F]fluoro-D-glucose, where the fluorine-18 (¹⁸F) isotope is a positron-emitting radionuclide. Because many diseases, including cancer, inflammatory processes, and neurological disorders, are associated with altered glucose metabolism, FDG-PET has become an indispensable tool in clinical diagnosis, staging, and treatment monitoring.
- Once administered, typically via intravenous injection, FDG behaves similarly to glucose and is transported into cells through glucose transporters. Inside the cell, it undergoes the first step of glycolysis—phosphorylation by hexokinase to FDG-6-phosphate—but unlike glucose, FDG cannot proceed further in the metabolic pathway. As a result, it becomes metabolically trapped within cells, especially those with high metabolic rates, such as malignant tumor cells, active inflammatory cells, or specific regions of the brain and heart. The accumulated positron-emitting FDG then emits radiation, which is captured by PET scanners to generate detailed images that reflect regional metabolic activity.
- In oncology, FDG-PET is a cornerstone of modern imaging. Cancer cells often exhibit increased glucose metabolism, known as the Warburg effect, and thus accumulate FDG at higher concentrations than normal tissues. FDG-PET enables early detection of tumors, accurate staging of cancer, assessment of metastasis, and monitoring of therapeutic response or recurrence. It is particularly effective in evaluating lymphomas, lung cancer, colorectal cancer, breast cancer, and melanoma.
- In neurology, FDG-PET is used to study cerebral metabolism and detect areas of hypo- or hypermetabolism in conditions such as Alzheimer’s disease, epilepsy, Parkinson’s disease, and brain tumors. For example, reduced FDG uptake in the parietal and temporal lobes is characteristic of Alzheimer’s disease. In epilepsy, FDG-PET may identify the epileptogenic focus during interictal periods, aiding in surgical planning for patients with intractable seizures.
- In cardiology, FDG-PET can differentiate between viable and non-viable myocardium in patients with ischemic heart disease. Myocardial segments that retain FDG uptake but show impaired function on perfusion scans are considered viable and may benefit from revascularization procedures.
- Despite its many advantages, FDG-PET has limitations. Not all tumors show high FDG uptake (e.g., prostate cancer or certain indolent lymphomas), and FDG also accumulates in non-malignant tissues with high metabolic activity, such as the brain, heart, and sites of inflammation or infection. This can result in false positives or complicate interpretation. Additionally, patients must often fast before the scan to ensure low insulin levels and optimize FDG distribution, and glucose levels must be controlled, especially in diabetic patients, to avoid altered tracer uptake.
- FDG is produced in a cyclotron due to the short half-life of fluorine-18 (approximately 110 minutes), requiring the compound to be synthesized and transported efficiently for clinical use. Its production and handling demand strict regulatory compliance to ensure safety, sterility, and radiochemical purity.
