Optimization and comparison of [18F]FET synthesis on two distinct automated radiochemistry systems

<i>O</i>-(2-[¹⁸F]Fluoroethyl)- <i>_L</i> -tyrosine ([¹⁸F]FET) is a promising amino acid PET tracer for assessment of malignant brain tumors. Herein, we report optimized production of [¹⁸F]FET for clinical use on two commercial radiochemistry systems: Sofie ELIXYS and GE FASTlab 2. While the Sofie ELIXYS procedure requires high performance liquid chromatography (HPLC) purification, the GE FASTlab 2 method uses solid-phase extraction (SPE) purification. In both cases, [¹⁸F]FET met release specifications for clinical investigation laid out in the United States Pharmacopeia (USP) and/or European Pharmacopeia (Ph. Eur.). The radiochemical yield of [¹⁸F]FET was 35-55% and 30-55% decay corrected to start of synthesis (SOS) for Sofie ELIXYS and GE FASTlab 2, respectively. The overall synthesis time was 75-85 and 70-80 min from SOS for Sofie ELIXYS and GE FASTlab 2, respectively. The radiochemical purity was > 99%, and the molar activity (A_m) was 340-464 GBq/µmol at end of synthesis (EOS).