Fluorodeoxyglucose – This is a radiopharmaceutical analog of glucose used in PET scanning. It is injected into the veins with the circulation then distributing it throughout the body. Cells that use a high amount of glucose (brain, kidney and cancer cells) will absorb this molecule and partially metabolize it. The byproducts with an attached radioisotope will remain in the cell until the isotope decays thus the cell is “marked” by the isotope. PET scanning will identify areas rich in the isotope, creating an image that shows areas where a high amount of metabolism of the FDG is occurring.
18F-FDG, as a glucose analog, is taken up by high-glucose-using cells such as brain, kidney, and cancer cells, where phosphorylation prevents the glucose from being released again from the cell, once it has been absorbed. The 2′ hydroxyl group (—OH) in normal glucose is needed for further glycolysis (metabolism of glucose by splitting it), but 18F-FDG is missing this 2′ hydroxyl. Thus, in common with its sister molecule 2-deoxy-D-glucose, FDG cannot be further metabolized in cells. The 18F-FDG-6-phosphate formed when 18F-FDG enters the cell thus cannot move out of the cell before radioactive decay. As a result, the distribution of 18F-FDG is a good reflection of the distribution of glucose uptake and phosphorylation by cells in the body.