Unsuspected reduced radiochemical purity of the 18 F-FDG may decrease image resolution, SUV reliability and diagnostic accuracy.

OBJECTIVE: Our aim was to identify the conditions required to stably maintain the radiochemical purity of fluorine-18-fluorodeoxyglucose (18 F-FDG) above the Korean Pharmacology (KP) and United States Pharmacology (USP) standards for expiration time (time from the end of synthesis (EOS), 8h even at a high radioactive concentration exceeding 7.4GBq/mL.

SUBJECTS AND METHODS: The changes in the radiochemical purity of 18 F-FDG were assessed according to the changes in radioactive concentration, ethanol (EtOH) concentration, amount of water for dilution storage temperature, and storage volume.

RESULTS: Controlling the radioactive concentration as much as possible during the production of 18 F-FDG is necessary to improve the radiochemical purity of 18 F-FDG. In the production of 18 F-FDG, a radioactive concentration <7.4GBq/mL was sufficient to maintain the radiochemical purity above the KP and USP standards for 10h after the EOS. If the radioactive concentration exceeded 7.4GBq/mL during synthesis, the addition of EtOH to 18 F-FDG is essential to maintain the radiochemical purity above the KP and USP standards. To minimize residual solvent EtOH production, the addition of 0.1% EtOH to the 18 F-FDG is the ideal combination.

CONCLUSION: Increasing the radiochemical purity of the 18 F-FDG increases the quality of images, the reliabity of the SUV during PET scanning and consequently increases the accuracy of diagnosis. Furthermore, 18 F-FDG can be synthesized at a high radioactive concentration in large volume, and its effective date could also be prolonged.