Objective: To assess a commercially available cassette for the fully automated production of 3'-deoxy-3'-[¹⁸F]fluorothymidine ([¹⁸F]FLT), and to develop a quality control method for this synthesis.

Background: [¹⁸F]FLT, a tracer of cellular proliferation, has been used clinically at the Queensland P.E.T. Service since 2007. The radiosynthesis employed was that of Machulla (2001) with the 5'-O-benzoyl-2,3'-anhydrothymidine precursor (DMSO method) and High Performance Liquid Chromatography (HPLC) using the TRACERlab_FX-FN synthesis module (GE Healthcare). More recently, a disposable cassette along with a chemical reagents kit has become commercially available for use on the TRACERlab_MX (GE Healthcare) - typically used for [¹⁸F]FDG production. The cassette-based radiosynthesis differs markedly to that used previously dictating a review of quality control procedures. Differences include: precursor, solvent, phase transfer catalyst, hydrolysis, and cartridge rather than HPLC purification.

Method: Three batches of [¹⁸F]FLT were produced using a modified [¹⁸F]FDG sequence, cassettes, and chemical reagent kits from ABX Chemicals. The radiochemical purity was determined by HPLC with a C-18 column using UV and radio-detection. Comparison was made to reference solutions of the potential contaminants. Chemical purity was also determined by HPLC as above, however the phase transfer catalyst, tetra butyl ammonia (TBA), required a different column and electrochemical detection.

Conclusion: Although variable (5-10% yield end of synthesis), the cassette-based synthesis gave higher radiochemical yields than that of the DMSO method. All previously established product specifications were met. The quality control procedure was modified in order to assess any 'new' contaminants and a HPLC method was developed for the analysis of TBA.