From the Guidelines
FDG-PET works by detecting areas of high glucose metabolism in the body, which is particularly useful for identifying cancer cells, through the use of a radioactive tracer called fluorodeoxyglucose (FDG) that accumulates in tissues proportional to glucose utilization. The process involves the injection of FDG, an analogue of glucose, which is taken up by living cells via cell membrane glucose transporters and subsequently incorporated into the first step of the normal glycolytic pathway 1. As the radioactive fluorine atoms decay, they emit positrons that collide with nearby electrons, producing gamma rays traveling in opposite directions, which are then detected by the PET scanner to create three-dimensional images showing where the FDG has accumulated in the body.
Key Steps in the FDG-PET Process
- Injection of the FDG tracer, which is a glucose analogue labeled with a radioactive isotope of fluorine (F-18) 1.
- Uptake of FDG by cells, with cancer cells typically consuming more glucose and thus taking up more of the FDG tracer due to overexpression of GLUT glucose transporters and increased hexokinase activity.
- The FDG becomes trapped inside cells because it cannot be fully metabolized like regular glucose.
- Decay of the radioactive fluorine atoms, emitting positrons that collide with electrons to produce gamma rays.
- Detection of these gamma rays by the PET scanner to create images of FDG accumulation.
Importance of FDG-PET in Clinical Practice
The use of FDG-PET, especially in combination with CT (FDG-PET/CT), provides essential information for radiation treatment planning, helping with critical decisions when delineating tumor volumes 1. It has been proven to be a sensitive imaging modality for the detection, staging, and restaging, as well as therapy response assessment in oncology. The technique allows for noninvasive quantitative assessment of biochemical and functional processes, making it a valuable tool in the management of cancer patients.
From the FDA Drug Label
Fludeoxyglucose F 18 Injection, USP is a positron emitting radiopharmaceutical containing no-carrier added radioactive 2-deoxy-2-[18F]fluoro-D-g1ucose, which is used for diagnostic purposes in conjunction with Positron Emission Tomography (PET). Fluorine F 18 decays by positron (β+) emission and has a half-life of 109.7 minutes. The principal photons useful for diagnostic imaging are the 511 keV gamma photons, resulting from the interaction of the emitted positron with an electron.
FDG-PET Mechanism: Fluorodeoxyglucose-Positron Emission Tomography (FDG-PET) works by using a radiopharmaceutical, Fludeoxyglucose F 18, which is a glucose analog that is taken up by cells with high glucose metabolism. The radiopharmaceutical decays by positron emission, producing gamma photons that are detected by the PET scanner, allowing for the visualization of areas with high glucose metabolism. Key points:
- Positron Emission: Fluorine F 18 decays by positron emission.
- Gamma Photons: The principal photons useful for diagnostic imaging are the 511 keV gamma photons.
- Diagnostic Purpose: Used for diagnostic purposes in conjunction with Positron Emission Tomography (PET) 2.
From the Research
Overview of FDG-PET
- FDG-PET (Fluorodeoxyglucose-Positron Emission Tomography) is a diagnostic imaging technique that allows identification of biochemical and physiologic alterations in tumors 3.
- It is based on the increased glucose consumption of cancer cells, which have an increased demand for glucose 4.
Mechanism of FDG-PET
- FDG-PET works by using a radioactive derivative of glucose, 2-(18)F-fluoro-2-deoxy-D-glucose (FDG), which is taken up by cancer cells due to their increased glucose metabolism 4.
- The FDG uptake in tumors is proportional to the metabolic rate of viable tumor cells 3.
- The high sensitivity and high negative predictive value of FDG-PET in most malignant tumors enable this technique to play a significant role in tumor management at initial staging and follow-up 3.
Applications of FDG-PET
- FDG-PET is clinically useful in the detection of cancer, the differentiation of malignant and benign lesions, the staging of cancer before therapy, and the assessment of cancer therapy, as well as for determining the recurrence after therapy of most cancers 4.
- It is also used in radiation oncology for tumor imaging and radiotherapy planning 5.
- FDG-PET/CT has become the new standard approach to imaging in the diagnosis and management of many cancer patients, including those with breast cancer 6.
Limitations and Future Directions
- There are some limitations to FDG-PET, such as low FDG uptake in some cancers and substantial FDG uptake in inflammatory cells 4.
- Integrated PET/CT systems have overcome some of these drawbacks by providing both anatomical and functional imaging at the same position 4.
- Other metabolic PET imaging agents, such as radiolabeled amino acids, are being developed to improve the specificity and sensitivity of PET imaging in cancer diagnosis and management 5.