Synthesis and biological evaluation of [18F]tetrafluoroborate: a PET imaging agent for thyroid disease and reporter gene imaging of the sodium/iodide symporter

Abstract

PurposeThe human sodium/iodide symporter (hNIS) is a well-established target in thyroid disease and reporter gene imaging using gamma emitters 123I-iodide, 131I-iodide and 99mTc-pertechnetate. However, no PET imaging agent is routinely available. The aim of this study was to prepare and evaluate 18F-labelled tetrafluoroborate ([18F]TFB) for PET imaging of hNIS.Methods[18F]TFB was prepared by isotopic exchange of BF4− with [18F]fluoride in hot hydrochloric acid and purified using an alumina column. Its identity, purity and stability in serum were determined by HPLC, thin-layer chromatography (TLC) and mass spectrometry. Its interaction with NIS was assessed in vitro using FRTL-5 rat thyroid cells, with and without stimulation by thyroid-stimulating hormone (TSH), in the presence and absence of perchlorate. Biodistribution and PET imaging studies were performed using BALB/c mice, with and without perchlorate inhibition.Results[18F]TFB was readily prepared with specific activity of 10 GBq/mg. It showed rapid accumulation in FRTL-5 cells that was stimulated by TSH and inhibited by perchlorate, and rapid specific accumulation in vivo in thyroid (SUV = 72 after 1 h) and stomach that was inhibited 95% by perchlorate.Conclusion[18F]TFB is an easily prepared PET imaging agent for rodent NIS and should be evaluated for hNIS PET imaging in humans.Electronic supplementary materialThe online version of this article (doi:10.1007/s00259-010-1523-0) contains supplementary material, which is available to authorized users.