Dependence of 18F Production Yield and Radioactive Impurities on Proton Irradiation Dose

Radiation safety for patients during positron emission tomography (PET) procedures is affected by the amount of radioactive impurities generated during production of fluorine-18 (18F) radionuclide. In this investigation, the dependence of 18F production yield and radioactive impurities on proton irradiation dose is discussed. Enriched water (H2O18) target was bombarded perpendicularly by 11-MeV proton beams at various proton doses. Experimental results indicated that the 18F radioactivity yield and the amount of 56Co and Ag110m radioactive impurities depend strongly on the proton dose. In the proton dose range between 2 μAhr and 20 μAhr, the radioactive impurities increased with increasing proton dose. There was no significant difference in the radioactivity yield of both 56Co and Ag110m impurities at low proton dose between 2 and 10 μAhr. However a huge difference was recorded when the dose was increased above 10 μAhr. The experimental data can be used to predict the amount of impurities generated during 18F production at proton dose of higher than 20 μAhr.