Page "Positron emission tomography" Paragraph 44

Oncology: PET scanning with the tracer fluorine-18 ( F-18 ) fluorodeoxyglucose ( FDG ), called FDG-PET, is widely used in clinical oncology.

This tracer is a glucose analog that is taken up by glucose-using cells and phosphorylated by hexokinase ( whose mitochondrial form is greatly elevated in rapidly growing malignant tumours ).

A typical dose of FDG used in an oncological scan is 200-400 MBq for an adult human.

Because the oxygen atom that is replaced by F-18 to generate FDG is required for the next step in glucose metabolism in all cells, no further reactions occur in FDG.

Furthermore, most tissues ( with the notable exception of liver and kidneys ) cannot remove the phosphate added by hexokinase.

This means that FDG is trapped in any cell that takes it up, until it decays, since phosphorylated sugars, due to their ionic charge, cannot exit from the cell.

This results in intense radiolabeling of tissues with high glucose uptake, such as the brain, the liver, and most cancers.

As a result, FDG-PET can be used for diagnosis, staging, and monitoring treatment of cancers, particularly in Hodgkin's lymphoma, non-Hodgkin lymphoma, and lung cancer.

Many other types of solid tumors will be found to be very highly labeled on a case-by-case basis — a fact that becomes especially useful in searching for tumor metastasis, or for recurrence after a known highly active primary tumor is removed.

Because individual PET scans are more expensive than " conventional " imaging with computed tomography ( CT ) and magnetic resonance imaging ( MRI ), expansion of FDG-PET in cost-constrained health services will depend on proper health technology assessment ; this problem is a difficult one because structural and functional imaging often cannot be directly compared, as they provide different information.

Oncology scans using FDG make up over 90 % of all PET scans in current practice.