EFFICIENCY OF AN IN-LINE CHARCOAL FILTER IN AUTOMATED CHEMISTRY PROCESS-CONTROL UNIT DURING THE SYNTHESIS OF F-18 FLUORODEOXYGLUCOSE (FDG)

F-18 fluoride ion is produced by bombarding O-18 enriched water using an 11 MeV negative ion Radioisotope Delivery System (RDS-112) cyclotro n by O-18(p,n)F-18 reaction. During the synthesis of F-18-FDG, a gaseo us effluent containing F-18 is released. To quantitate the loss of F-1 8 during the synthesis, the F-18 activity at the end of bombardment de livered to chemical process control unit (CPCU), the amount of F-18-FD G produced, the residual activity in CPCU, the activity trapped in cha rcoal filter, reaction vessels, cartridge and resin column were measur ed. A dose calibrator was used to assay total F-18 delivered to the CP CU and FDG produced. All other measurements were with a calibrated ion ization chamber in a fixed geometry. The amount of gaseous F-18 releas ed was calculated. For routine productions, conversion of F-18 into FD G was 46.0 +/- 4.0%. In six production runs without a charcoal filter, the mean gaseous release of F-18 was 10.6 +/- 1.0%. With an activated charcoal filter retrofitted to the exhaust of the CPCU, then mean gas eous F-18 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 c olumn. The efficiency of a charcoal filter for trapping F-18 gaseous e ffluent during synthesis was found to be >99.0%.