[11C] Methionine as PET radiopharmaceutical produced at CDTN/CNEN

Carbon-11 (11C) is an attractive radionuclide used in positron emission tomography (PET) since carbon is a ubiquitous element in biomolecules. Positron emitter-labeled amino acids are being widely used as indicators of tumor activity due to enhanced expression of amino acid transporter systems in cancer cells. L-[Methyl-(11C)] Methionine or [11C]Methionine is being used in neuro-oncology and, unlike 2-[18F]fluoro-2-deoxy-D-glucose (18FDG), gives more contrast images and improves brain tumor diagnosis. The aim of this work was to develop the synthesis and quality control of [11C]Methionine at the Radiopharmaceuticals Research and Production Facility (UPPR) of CDTN/CNEN. The synthesis of [11C] Methionine was performed using two Sep-Pak tC18 plus cartridges one as solid support for the 11C-methylation of the precursor L-homocysteine thiolactone hydrochloride and another for purification. The pH, radionuclidic identity and purity, residual solvents, radiochemical and chemical purity of the final product were evaluated as described on the European Pharmacopoeia 7.0 monograph. Total synthesis time was 18 minutes, the radiochemical yield was approximately 15% (non-decay corrected) and radiochemical purity was greater than 95%. [11C]Methionine was successfully synthesized at CDTN using the described procedures and complied with quality requirements. Due to the rapid growth of oncologic PET scans in last decade, 11C labelling holds great promises in the next few years with the application of other tracers beyond 18FDG. This pioneering work of UPPR/CDTN represents a response to the demands of a growing nuclear medicine in the country focused on achieving better diagnostic imaging. (author)