Optimization of Automated Solid Phase Extraction-based Synthesis of [18F]Fluorocholine

Abstract

[18F]Fluorocholine is a radiopharmaceutical used non-invasively in positron emission tomography to diagnose parathyroid adenoma, prostate cancer, and hepatocellular carcinoma by evaluating the choline metabolism. In this study, a radiolabeling method for [18F]fluorocholine was optimized using a solid phase extraction (SPE) cartridge. [18F]Fluorocholine was labeled in two steps using an automated synthesizer. In the first step, dibromomethane was reacted with [18F]KF/K2.2.2/K2CO3 to obtain the intermediate [18F]fluorobromomethane. In the second step, [18F]fluorobromomethane was passed through a Sep-PakⓇ Silica SPE cartridge to remove the impurities and then reacted with N,N-dimethylaminoethanol (DMAE) in a Sep-PakⓇ C18 SPE cartridge to label [18F]fluorocholine. The reaction conditions of [18F]fluorocholine were optimized. The synthesis yield was confirmed according to the number of silica cartridges and DMAE concentration. No statistically significant difference in the synthesis yield of [18F]fluorocholine was observed when using four or three silica cartridges (P＞0.05). The labeling yield was 11.5±0.5% (N=4) when DMAE was used as its original solution. On the other hand, when diluted to 10% with dimethyl sulfoxide, the radiochemical yield increased significantly to 30.1±5.2% (N=20). In conclusion, [18F]Fluorocholine for clinical use can be synthesized stably in high yield by applying an optimized synthesis method.

Keywords

• fluorine-18
• [18f]fluorocholine
• radiopharmaceuticals
• solid phase extraction