18FDG (18F fluorodeoxyglucose)
18FDG is the radiopharmaceutical used in PET imaging at Terre Haute Medical Laboratory/Union Hospital. 18FDG is produced in an automated radiochemical synthesis unit from cyclotron produced Fluorine F-18. Fluorine F-18 is produced by proton bombardment of enriched [18O] water and is bound to mannose triflate under stereo passage through an ion retardation resin.
Fluorine F-18 decays by positron (b+) emission and has a half-life of 109.8 minutes. Because of its relatively short half-life, the amount of radiation exposure a patient receives from 18FDG PET imaging is about the same as from two chest radiographs. 18FDG is a glucose analogue which concentrates in cells that rely upon glucose as a primary energy source. Once inside a cell 18FDG is phosphorylated and cannot exit. Regions of increased 18FDG uptake correlate with increased glucose metabolism. Although all cells use glucose, cancer cells are highly metabolic and utilize more glucose than neighboring cells. The accumulation of 18FDG in the cancer cells results in more radioactivity coming from that area and shows up as areas that "light up" on the PET images. These areas are referred to as "hot spots"-areas of increased 18FDG accumulation.
18FDG is cleared from non-cardiac tissues within 3 to 24 hours after administration. 18FDG that is not involved in glucose metabolism is excreted unchanged in the urine. Therefore, many times a urinary catheter is placed in the urinary bladder to prevent the 18FDG from accumulating in the bladder and distorting the images.
There are no adverse reactions that require medical intervention associated with the injection of 18FDG. Since it is not contrast material, patients who are allergic to x-ray dye can receive 18FDG without any complications. 18FDG that is retained in the body and not excreted is no longer radioactive after about 18 hours.
