Efficiency of an in-line charcoal filter in automated chemistry process control unit during the synthesis of¹⁸F-fluorodeoxyglucose (FDG)

Abstract

¹⁸F fluoride ion is produced by bombarding¹⁸O enriched water using an 11 MeV negative ion Radioisotope Delivery System (RDS-112) cyclotron by¹⁸O(p,n)¹⁸F reaction. During the synthesis of¹⁸F-FDG, a gaseous effluent containing¹⁸F is released. To quantitate the loss of¹⁸F during the synthesis, the¹⁸F activity at the end of bombardment delivered to chemical process control unit (CPCU), the amount of¹⁸F-FDG produced, the residual activity in CPCU, the activity trapped in charcoal filter, reaction vessels, cartridge and resin column were measured. A dose calibrator was used to assay total¹⁸F delivered to the CPCU and FDG produced. All other measurements were with a calibrated ionization chamber in a fixed geometry. The amount of gaseous¹⁸F released was calculated. For routine productions, conversion of¹⁸F into FDG was 46.0±4.0%. In six production runs without a charcoal filter, the mean gaseous release of¹⁸F was 10.6±1.0%. With an activated charcoal filter retrofitted to the exhaust of the CPCU, then mean gaseous¹⁸F activity released was 1.2±1.2%. The residual activity in the synthesis unit was 12.9±3.5%. The remaining activity i.e. 33.1±4.2%, was in the reaction vessels, cartridges and in the resin column. The efficiency of a charcoal filter for trapping¹⁸F gaseous effluent during synthesis was found to be >99.0%.