Autoradiolysis of Radiopharmaceutical 2-[18F]Fluorodeoxyglucose with Activity Concentrations of 4–5.5 GBq/mL

Abstract

The kinetics of the autoradiolytic decomposition of the radiopharmaceutical 2-[18F]fluorodeoxyglucose ([18F]FDG) with initial activity concentrations of 4.02–5.45 GBq/mL in physiological saline solution has been studied. It has been shown that an increase in the initial activity concentration or a decrease in the concentration of ethanol (chemical impurity) leads to a greater buildup of radiolytic [18F]fluoride and a decline in the radiochemical purity of the drug. During storage of the radiopharmaceutical, a decrease in the concentration of ethanol and the formation of acetaldehyde, a product of its radiation-induced transformations, have been detected, the aldehyde concentration correlating with the relative activity of [18F]fluoride. It has been found that after storage of [18F]FDG with the same initial activity concentration in sealed 15-mL vials for 8 hours, the relative activity of [18F]fluoride is significantly higher in 8-mL than in 1.5-mL solutions. This difference may be due to both an increase in the dose absorbed by the drug and the inhibitory effect of oxygen on the autoradiolytic dehalogenation process. An [18F]fluoride removal procedure for purifying [18F]FDG is described, which ensures the preservation of aseptic and pyrogen-free injectable drugs under the conditions of an operating positron emission tomography center.