Consideration of the Residual Radioactivity of Amyloid Imaging Agent 18F-flutemetamol Adsorbed on Materials Used in Amyloid PET

Abstract

In an amyloid PET for visualizing amyloid beta plaque accumulated in the brain, an amyloid imaging agent generally tends to adsorb to the inner walls of materials used in routes of administration to the patient. Therefore, we evaluated the adsorption of the amyloid imaging agent 18F-flutemetamol by measuring the residual radioactivity of the injection route material (intravenous catheter, extension tube, three-way stopcock) and the dispensed material (needle, syringe) in 35 patients during amyloid PET. The average actual radioactivity administered to the patients was 188.5±6.0 MBq (mean±standard deviation). When the radioactive concentration was 66.5±14.5 MBq/ml, the residual radioactivity was 1.4±0.2% for the injection route material, 0.8±0.3% for the dispensed material and 2.2±0.5% for both materials added based on the radioactivity of the amyloid imaging agent 18F-flutemetamol used for administration to the patient. There was a correlation between radioactive concentration and residual radioactivity. As the radioactive concentration increased, the residual radioactivity of all the materials tended to increase. Validation of adsorption to the tube and other materials used to administer patients can predict the residual radioactivity of the amyloid imaging agent 18F-flutemetamol prior to administration.