This project began as an effort to prepare C-11 labeled raclopride. It has grown into a more general project to develop high specific activity 3-11 for the labeling a wide range of chemical compounds. We have successfully worked out the radiochemical synthesis of C-11 RO 15-1788, a benzodiazepine ligand, and raclopride, a dopamine D2 receptor antagonist. However, we still have not obtained products with high enough specific activity for use in live animal studies. The major effort on this project during this Fiscal Year was to improve the specific activity of our C-11 precursors. We have consulted with other PET/Cyclotron Centers and have adapted our system to improve the specific activity of our precursors. A new semi-remote handling system to allow very rapid trapping and transferring of C-11 labeled Carbon dioxide from the cyclotron target. Automation of this entire process to convert target C-11 carbon dioxide to C-11 Methyl iodide is now under development. The specific activity of the C-11 Carbon dioxide from the target is now at approximate 4 to 6 Ci/umol at end of bombardment. Because of the dilution of the specific activity in subsequent manipulations, this specific activity needs to be higher before we can achieve high specific activity labeled receptor ligands.
