[N-Methyl-11C]choline by on-column reaction: a study on [11C]CH3I incorporation and the residual amount of precursor in the product

High yield one-pot production of [18F]FCH via a modified TRACERlab FxFN module

INTRODUCTION

[¹⁸F]Fluoromethylcholine ([¹⁸F]FCH) is a potent tumors imaging agent. In order to fulfill the demand of pre-clinical and clinical studies, we have developed an automated high yield one-pot synthesis of this potent tumors imaging agent.

METHODS

[¹⁸F]FCH was synthesized using a modified TRACERlab Fx_FN module. Briefly, dibromomethane (10% in CH₃CN) was fluorinated with K[¹⁸F]/K _2.2.2 in a glassy carbon reaction vessel at 120°C for about 5min to generate [¹⁸F]fluorobromomethane ([¹⁸F]FBM). The resulting [¹⁸F]FBM was then bubbling (He, 700mL/min) through four Sep-Pak® Silica Plus Long cartridges to react with dimethylaminoethanol (10% DMAE in 0.3mL DMSO) which was pre-loaded on Sep-Pak® C₁₈ Plus Short cartridge. The [¹⁸F]FCH was purified by solid-phase extraction (SPE) using one Sep-Pak® C₁₈ Plus Short and one Sep-Pak® CM Plus Short in series. The quality of [¹⁸F]FCH synthesized by this method was verified by HPLC and TLC as compared to authentic sample.

RESULTS

Using this improved one-pot method, the RCY of [¹⁸F]FCH was 18.8 ± 2.1% (EOB, n = 27) in a synthesis time of 49 ± 5min from EOB. The radiochemical purity of [¹⁸F]FCH was greater than 90% and the residual DMAE concentration in the final product was less than 10ppm.

CONCLUSIONS

This optimized method could fulfill the demand of [¹⁸F]FCH for both pre-clinical and clinical studies, especially for nearby study sites without a cyclotron.