Physics, Techniques and Proceduresfluorodeoxyglucose (FDG)
glucose analogue and the compound predominantly used in
PET imaging
. F-18-2-fluoro-2-deoxyglucose (FDG) is a glucose analogue which competes with glucose in the hexokinase reaction, in which glucose is phosphorylated at the 6 position to form glucose-6-phosphate. In contrast to glucose, FDG-6-phosphate does not undergo glycolysis, and does not enter the fructose-pentose shunt or glycogen synthesis pathway. Thus, cellular FDG uptake reflects the overall rate of transmembranous exchange of glucose. The dephosphorylation of FDG is also slow and when modeling the behaviour of FDG (see
compartment modelling
), this reaction is negligible as long as the time from FDG injection is less than 60 minutes. Owing to the simple reaction pattern, the behaviour of FDG in brain is amenable to quantitative
compartment modelling
.
FDG-PET is useful in imaging the following tumors: it is taken up by
bronchial carcinoma, colorectal cancer, esophageal and gastric cancers, testicular, breast and other gynecological cancers, ENT cancers, lymphomas, melanomas and sarcomas. It shows little uptake in most prostate cancers, and cancers of the
renal collecting system, where an additional difficulty is distinguishing lesions from the normal urinary FDG excretion. It is probably not very useful in plasmacytoma/multiple myeloma. Additionally, FDG-PET may be an excellent marker for acute and chronic
inflammation, as it is avidly taken up by activated granulocytes and macrophages. This cells, when engaged in fighting
inflammation, undergo a so called metabolic burst, where glucose and thereby FDG uptake is increased manyfold.
GvS