Answer: Fluorodeoxyglucose is a radiolabeled tracer for imaging brains with positron emission tomography (PET scan).
A PET scan is a useful method for imaging the body, and especially the brain. In a PET scan, the patient is given an intravenous injection of a radionuclide, a radioactive compound that emits gamma rays. These gamma rays are then detected by a scanner. A computer then uses these images in order to create a 3D reconstruction of the body.
One of the most commonly used radionuclide is called fluorodeoxyglucose, or FDG. FDG is an analogue of glucose, the sugar molecule that acts as the primary source of energy for cells. The parts of the body that have a higher metabolic demand will show a stronger signal, as the radioactive fluorine [18F] will emit gamma rays.
Normally, a glucose molecule contains a hydroxyl group (-OH). This hydroxyl group is necessary for the next step of glucose metabolism, called glycolysis. However, fluorodeoxyglucose is lacking the -OH (hence, -deoxy-). As a result, the molecule will not undergo chemical breakdown.
PET scans are useful for detecting tumors. Since the tumor requires energy for growth, the radioactive signal will be much stronger where the tumor is located. PET scans can also be used to image parts of the brain that may be active under certain conditions.
The major downside to a fluorodeoxyglucose injection is the radioactivity. Increasing exposure to radioactive compounds increases the possibility of genetic mutation, which can harm the person.