Fast routine production of image-[11C-methyl]methionine with Al2O3KF

No-carrier-added (nca) image-[11C-methyl]methionine was prepared via the very fast S-alkylation of image-homocysteine adsorbed on Al2O3/KF with [11C]iodomethane at room temperature in ethanol. The alkylation was realized with a radiochemical yield of 94 ± 4% EOB (n = 20). More than 90% (n = 20) of the precursor image-homocysteine remained adsorbed on the solid support and was eliminated by a simple filtration. After reaction, neither racemization nor by-product were detected. The purification process was thus limited to a C18 Sep-Pak followed by an alumina Sep-Pak. The radiochemical purity measured on the final solution was shown to be > 99%. The only chemical contaminant was image-homocysteine (± 10 μg). With this new technique, image-[11C-methyl]methionine was ready for injection within 10 min from [11C]CO2 with a specific activity ranging around 37 ± 5.6 GBq (1 ± 0.15 Ci)/μmol EOB. Through this procedure image-[11C-methyl]methionine can be prepared without preparative HPLC purification. This is an important simplification for the fast routine production of one of the most widely used radiopharmaceutical compounds for PET.