Formation of Cd radionuclide impurities during F production.

Cd isotopes (Cd and Cd) are generated from the silver target body during the bombardment of [O]water in the routine production of 2-[18F]fluoro-2-deoxy-d-glucose ([F]FDG) for PET (Positron Emission Tomography) diagnosis. Cadmium isotopes contribute significantly to the total activity of generated impurities and, due to being potentially radiotoxic to living organisms, they should be effectively reduced from FDG to prevent accidental injection of even small concentrations into patients. Purification of the final [F]FDG can be based on a set of columns, fulfilling various functions in the cleaning process. To assess cadmium impurities and the efficiency of the purification process, a low background gamma spectrometry system with high resolution has been applied. Even activity of 3.5 kBq and 290 kBq has been measured on QMA (Sep-Pak Light Accell Plus QMA) columns for Cd and Cd isotopes, respectively. Cd activity in the five column set was higher than that of Cd. The rate of F production process was about 1 GBq/min, while that of Cd and Cd radionuclides was about 4.2 kBq/min and 50 Bq/min respectively. The same purification efficiency of both isotopes has been obtained at each step of the process. The production rate of Cd and Cd radionuclides was insignificant compared to the F production rate. Therefore [F]FDG final product for use in injections before PET diagnostics was efficiently purified from cadmium radionuclide impurities.