Preparation of the hypoxia imaging PET tracer [18F]FAZA: reaction parameters and automation

18F-labeling of the nitroimidazole nucleoside analogue 1-(5-fluoro-5-deoxy-α-D-arabinofuranosyl)-2-nitroimidazole (FAZA) was developed to use this tracer in PET for detection of hypoxia. Parameters for labeling and hydrolysis were optimized with regard to amount of precursor, temperature and time. Labeling yields reached a maximum of 62±4% at 100 °C within 5 min using 5 mg of precursor. Hydrolysis was best performed with 1 mL of 0.1 N NaOH at 20 °C for 2 min. Transfer of these conditions to an automated synthesizer resulted in an overall radiochemical yield of 20.7±3.5%. Absolute yields at EOS were 9.8±2.3 GBq of [18F]FAZA ready for injection (n=21; 50 min after EOB; irradiation parameters: 35 μA, 60 min). Thus, a convenient approach suitable for large-scale production of [18F]FAZA was developed by an automated process.