[WHAT IS FDG?]

2009 Collected and organized by:

Haya Al-Thuwaini, Shatha Al-Mushait, Nora Al-Ohaly, Khulod Al-Washmi, Aaliah Alqahtani , Aalia BaFqeeh

FDG

     Fluorodeoxyglucose is a glucose analog. Its full chemical name is 2-fluoro-2-deoxy-D-glucose, commonly abbreviated to FDG.

it is a compound in which a radioactive fluoride atom which was produced in a cyclotron  is attached to a molecule of glucose. Once in the body, the FDG molecule is absorbed by various tissues just as normal glucose would be, and the radiation from the fluorine is used to map the distribution of glucose within the patient. 

     FDG works well to detect tumors because it can avidly concentrate in cancerous tissue. it looks like sugar to the tumor, so it tends to gobble it up. Because it isn’t the sugar the tumor is used to, it really can’t use it; it gets stuck there, and you have a chance to image it. Basically, you’re fooling the tumor into thinking that it’s taking up something that it needs. 

 

     It has been understood for over 5o years, that cancer cells, in general, have increased glucose uptake and anaerobic metabolism compared to normal tissues. Like glucose, FDG is taken up into cells through glucose transport proteins (GLUT) and then phosphorylated by hexokinase to FDG-6-phosphate. the FDG-6-phosphate becomes trapped in tissue in proportion to the rate of glycolysis. This accumulation of 18F-FDG-6-phosphate forms the basis of tumor metabolic imaging with PET. 

 

FDG is most used in the medical imaging modality positron emission tomography (PET),in which a compound is labeled with a radioisotope tracer and injected into a patient. In a typical procedure, a patient is injected with FDG — a dose of 5–10 millicuries — after not eating for four hours. After a 60–120 minute wait, during which time the patient is asked to remain still and quiet while the compound travels through the body, he or she lies down under the camera system and is imaged .The scanner reads the 511-keV gamma photon resulting from the interaction of the FDG-emitted positrons with electrons in the body at locations where the FDG has become concentrated. A computer then converts the data to images for physicians to examine. 

 

     Because the half-life of the F-18 radioisotope is short, 109.8 minutes, and because the compound is also excreted in urine, there is no need for the patient to take extra precautions due to the radiation—most of the compound is gone by the time the examination is over and the patient is free to leave.

References

http://www.ans.org/pubs/magazines/nn/docs/1999-11-2.pdf

http://www.molecularimagingcenter.org/index.cfm?PageID=7834&RPID=7165#PET scan, PET scanner

http://en.wikipedia.org/wiki/FDG

http://www.rxlist.com/fludeoxyglucose-drug.htm