Synthesis of ¹¹C-methionine on home-made module by the improved LOOP method

Objective The synthesis of radiopharmaceutical ¹¹C-methionine(¹¹C-MET) by LOOP and C-18 on-column method on home-made ¹¹C-multifunction synthesis module was compared. Method The synthesis conditions of ¹¹C-MET with home-made synthesis module by LOOP method was studied, which included the alkali equivalent, solvents and the amount of precursor.

Results The optimum condition was 2-3 mg of precursor in NaOH solution(2 mol/L), alkali equivalent(5.6-11.5 eq) and ethanol(100 μL), and at room temperature for synthesis of ¹¹C-MET. It could be got with radiochemical yield of (65.31±4.32)%(n=24, end of synthesis of ¹¹C-CH₃I). The radiochemical purity of ¹¹C-MET was higher than 95% and the production radioactivity was (6.61±1.38) GBq(n=24).

Conclusions By the method of LOOP, it showed that the production efficiency was increased, the output was increased and production cost of synthetic was reduced. The synthetic process was reliable and full automatic, and the product synthesized by this process was suitable for clinical use.