The PET Scan, a Chemist’s View

This entry is part 2 of 3 in the series "Radiation" --

Liam had a Positron Emission Tomography (PET) scan on 19Sept2014. For this the radioactive tracer is Fludeoxyglucose (18F) or (18F-FDG) for short. For those of you crazy chemistry people out there (like Jenn and myself), check this out:

a)Fludeoxyglucose b) β+ Decay of a proton emits a positron (and changes Fluorine to Oxygen); Since a positron is the antimatter equivalent of an electron, when it finds the closest electron it will annihilate. The matter will cease to exist, and it will turn into energy in the form of light (gamma rays). The two gamma rays produced each will have 511 keV of energy. c) With a little acid, the product will be glucose and continue through the energy cycle in the cell. Until the radioactive decay, the molecule is stuck. There is no chemistry available to the cell to process the glucose with substituted Fluorine, once the F gets converted to a hydroxyl, the chemistry can proceed as normal (With a heavy, but stable Oxygen atom)

The 18F-FDG looks just like the glucose molecule except for a heavy fluorine in place of the  2′ hydroxyl group.  Since all cells use glucose as a power source, the PET scan exploits the fact that cancer cells require more energy, and they will take up more of the compound than normal cells. The areas of the body emitting large amounts of gamma radiation are likely to have concentrations of cancer cells.

For those of you (and I know who you are) who would like even more information, here are some links that I found helpful when I was coming up to speed on the technique:

Fludeoxyglucose (18F)

Positron Emmision Tomography

A Molecular Imaging Primer: Modalities, Imaging Agents, and Applications (scroll down to figure 13)

Decay scheme of 18F