Automated production of 18F-rhodamine 6G for myocardial perfusion imaging

Objectives We previously reported a two-step synthesis of ¹⁸F-rhodamine 6G (¹⁸F-R6G) for myocardial perfusion imaging [1, 2]. Unfortunately, the automation of this synthesis proved challenging. We therefore developed a one-step synthesis for use with automated synthesis systems that can be used in future clinical studies with this compound.

Methods ¹⁸F-R6G was synthesized in GE Tracer lab FX N and Siemens Explora GN synthesizers from a R6G diethylene glycol tosylate ester precursor (1 mg) and azeotropically dried ¹⁸F/Kryptofix 2.2.2-K2CO3 in DMSO (1 mL) for 100 ^oC/30 min, followed by RP-HPLC semi-prep purification (Luna® 10 µm, C18, 100 Å, 250 x 10 mm; 45/55 v/v 0.1 M citrate buffer, pH 2.7 /acetonitrile, flow rate 5 mL/min).

Results ¹⁸F-R6G was obtained ~7% radiochemical yield (RCY), >99% radiochemical purity (RCP), and high specific activity (90 ± 43 TBq/mM, n=5) at end of synthesis (EOS) in each system. The total synthesis time was 60 min.

Conclusions ¹⁸F-R6G can be reproducibly synthesized using two different automated synthesis systems in good RCY, high RCP and high specific activity facilitating production for future clinical studies.

Research Support 5R01HL108107, Children’s Hospital Radiology Foundation.