Radiosynthesis challenges of 11C and 18F-labeled radiotracers in the FX2C/N tracerlab and their validation through PET-MR imaging

Glucose is the renowned source of the energy for the cancer growth, that's the reason for [18F]FDG success and make it widely used radiotracer. Though [18F]FDG has its own inherent limitations therefore many tracers have been developed to target specific receptors, and other metabolic routes. We have used FX2C and FX2N Tracerlab modules for the synthesis of the [11C]methionine, [18F]choline and [18F]fluorodopa via nucleophilic pathway in FX2C/N module. [11C]methionine was standardized in FX2C module using two different precursors, and purified using C18 cartridge based technique. [18F]methylcholine was synthesized using dimethylaminoethanol precursor and purified using cartridge-based method. [18F]fluorodopa was synthesized using nucleophilic precursor and purified using in-built preparative HPLC on FX2N module. All radioactive intermediates and chemical impurities were evaluated by analytical HPLC. The radiochemical purity of D and L-[11C]methionine were 4.6 ± 3.2% and 95.4 ± 3.6% while other chemical impurities were less than prescribed limits with yield of 20 ± 5%. [18F]fluoromethylcholine was prepared with high radiochemical purity of 97.3 ± 2.6% with yield of 8 ± 3%. [18F]fluorodopa was synthesized with high radiochemical purity of 95.8 ± 1.4% with 15 ± 3% yield. The adaptation of [18F]fluorodopa synthesis to FX2N module via designing synthesis sequence and purified through on-line HPLC has provided high radiochemical purity. PET-MR imaging was done using these tracers which have validated the synthesis and their availability for future clinical applications. •Automated synthesis of [11C]-methionine, [18F]-methylycholine and [18F]-fluorodopa in Tracerlab FX2C/N.•[11C]-methionine, and [18F]-methylycholine were synthesized using cartridge-based method.•[18F]-fluorodopa was synthesized using nucleophilic precursor and purified via on-line preparative HPLC.