Radionuclide impurities in proton-irradiated [18O]H2O for the production of 18F-: activities and distribution in the [18F]FDG synthesis process.

Proton- and neutron-induced activation products in the components of a high-pressure [(18)O]H(2)O target vessel used for the production of (18)F(-) in a medical cyclotron have been identified using high resolution gamma spectrometry. The activities leached from the target vessel into the [(18)O]H(2)O during irradiation, and the distribution of the identified radionuclide impurities in the various cartridges and solutions used in the [(18)F]FDG synthesis process have been measured and are discussed from the perspective of waste disposal. The results indicate that, at the energies and beam currents employed, only a few, relatively short-lived radionuclides are present in the irradiated [(18)O]H(2)O, and that the activities involved (<10 kBq in each case) are well below typical exemption limits. Activities of beta-emitting (3)H in irradiated [(18)O]H(2)O, produced via the (18)O(p,(3)H)(16)O reaction, have also been determined using liquid scintillation spectrometry. Measured activity concentrations, in the range 150-180 kBq g(-1), are consistent with those reported by other workers. Analyses of the synthesised [(18)F]FDG confirm the radiochemical purity of the product, both for (3)H and for gamma-emitting radionuclides in the energy range 25-1650 keV.