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 [18O]H2O target vessel used for the production of 18F− in a medical cyclotron have been identified using high resolution gamma spectrometry. The activities leached from the target vessel into the [18O]H2O during irradiation, and the distribution of the identified radionuclide impurities in the various cartridges and solutions used in the [18F]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 [18O]H2O, and that the activities involved (<10 kBq in each case) are well below typical exemption limits. Activities of beta-emitting 3H in irradiated [18O]H2O, produced via the 18O(p,3H)16O 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 [18F]FDG confirm the radiochemical purity of the product, both for 3H and for gamma-emitting radionuclides in the energy range 25–1650 keV.