High molar activity [ 18 F]tetrafluoroborate synthesis for sodium iodide symporter imaging by PET.

Background: Sodium iodide symporter (NIS) imaging by positron emission tomography (PET) is gaining traction in nuclear medicine, with an increasing number of human studies being published using fluorine-18 radiolabelled tetrafluoroborate ([ ¹⁸ F]TFB). Clinical success of any radiotracer relies heavily on its accessibility, which in turn depends on the availability of robust radiolabelling procedures providing a radiotracer in large quantities and of high radiopharmaceutical quality.
Results: Here we publish an improved radiolabelling method and quality control procedures for high molar activity [ ¹⁸ F]TFB. The use of ammonium hydroxide for [ ¹⁸ F]fluoride elution, commercially available boron trifluoride-methanol complex dissolved in acetonitrile as precursor and removal of unreacted [ ¹⁸ F]fluoride on Florisil solid-phase extraction cartridges resulted in the reliable production of [ ¹⁸ F]TFB on SYNTHRA and TRACERLAB FX _FN automated synthesizers with radiochemical yields in excess of 30%, radiochemical purities in excess of 98% and molar activities in the range of 34-217 GBq/µmol at the end of synthesis. PET scanning of a mouse lung tumour model carrying a NIS reporter gene rendered images of high quality and improved sensitivity.
Conclusions: A novel automated radiosynthesis procedure for [ ¹⁸ F]tetrafluoroborate has been developed that provides the radiotracer with high molar activity, suitable for preclinical imaging of NIS reporter gene.
(© 2022. The Author(s).)