Fluorodeoxyglucose Positron Emission Tomography
Fluorodeoxyglucose Positron Emission Tomography, commonly referred to as FDG-PET or PET-CT (when combined with computed tomography), is a medical imaging technique used to visualize metabolic activity within the body. Here’s how it works:
- FDG Tracer: The imaging process involves the use of a radioactive tracer called fluorodeoxyglucose (FDG). FDG is a glucose analog that is labeled with a radioactive isotope of fluorine (F-18). Glucose is the primary energy source for cells, and FDG is taken up by cells in proportion to their metabolic activity.
- Injection and Uptake: The patient is injected with FDG, typically intravenously. The FDG circulates in the bloodstream and is absorbed by tissues throughout the body, including areas of high metabolic activity such as cancer cells.
- PET Imaging: After a brief uptake period (typically about an hour), the patient undergoes PET imaging. A PET scanner detects the positrons emitted by the radioactive FDG tracer as it decays. Positrons are positively charged particles emitted during the decay process. When a positron encounters an electron within the body, they annihilate each other, emitting two gamma rays in opposite directions. The PET scanner detects these gamma rays and uses the information to create images that represent the distribution of FDG within the body.
- Combination with CT: In PET-CT imaging, a computed tomography (CT) scan is performed immediately after the PET scan. CT provides detailed anatomical images that help localize areas of abnormal FDG uptake seen on the PET scan. By combining metabolic information from PET with anatomical information from CT, PET-CT can provide more comprehensive diagnostic information than either modality alone.
FDG-PET imaging is widely used in oncology for cancer diagnosis, staging, restaging, treatment planning, and monitoring response to therapy. Cancer cells typically have increased metabolic activity compared to normal cells, leading to increased uptake of FDG and visualization on PET scans. FDG-PET is also used in cardiology, neurology, and other medical specialties for various diagnostic purposes.
It’s important to note that FDG-PET imaging involves exposure to ionizing radiation from the radioactive tracer. However, the benefits of the diagnostic information obtained from FDG-PET often outweigh the risks associated with radiation exposure, particularly in the context of cancer diagnosis and management. Additionally, FDG-PET scans are typically performed under the supervision of trained healthcare professionals in specialized imaging facilities.