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

European Journal of Nuclear Medicine and Molecular Imaging

Maite Jauregui-Osoro,1Kavitha Sunassee,1 Amanda J. Weeks,1 David J. Berry,1Rowena L. Paul,1 Marcel Cleij,1 J. Paul Banga,2 Michael J. O’Doherty,1 Paul K. Marsden,1 Susan E. M. Clarke,3 James R. Ballinger,3 Istvan Szanda,1 Sheue-Yann Cheng,4 Philip J. Blower1*

Maite Jauregui-Osoro,1Kavitha Sunassee,1 Amanda J. Weeks,1 David J. Berry,1Rowena L. Paul,1 Marcel Cleij,1 J. Paul Banga,2 Michael J. O’Doherty,1 Paul K. Marsden,1 Susan E. M. Clarke,3 James R. Ballinger,3 Istvan Szanda,1 Sheue-Yann Cheng,4 Philip J. Blower1*

1King’s College London, Division of Imaging Sciences

2King’s College London, Division of Cell and Gene Based Therapy

3Guy's and St Thomas' NHS Trust, Department of Nuclear Medicine

4Laboratory of Molecular Biology, National Cancer Institute, Bethesda, USA

Author for correspondence: Prof Phil Blower, King’s College London, Division of Imaging Sciences, 4th Floor Lambeth Wing, St Thomas’ Hospital, London SE1 7EH, UK Tel. +44-207-188-9513; Fax. +

Contents

  1. Optimisation of labelling conditions
  2. Uptake and efflux of [99m]Tc-pertechnetate in rat thyroid cells
  3. Comparison biodistribuition of [18F]-TFB and [99mTc]-pertechnetate in normal Balb/C mice

1. Optimisation of labelling conditions

Production of [18F]-BF4 by isotopic exchange

1 mL of a solution of NaBF4in 1M HCl at pH 0 was placed in a glass vial. A 1 mL aliquot of 18F- in water was added and the vial heated at 70oC for 10 minutes. Following the reaction, the vials were removed from the heat. 1 mL NaOH (1M) was added to each solution to neutralise the pH and prevent further exchange of 18F-.Exchange reactions were conducted in duplicate at the following concentrations of NaBF4: 10 mg/mL; 5 mg/mL; 1 mg/mL; 0.1 mg/mL. The reaction solutions were analysed by TLC as described in the Materials and Methods section.

Table OR1shows that the % 18F incorporation into the product increases with the concentration of cold NaBF4. Figure OR1 shows that there is a general upward trend in labelling with increase in precursor concentration

Precursor (NaBF4) concentration (mg/mL) / Mean yield (%)± Standard Deviation
Reaction 1 / Reaction 2 / Mean
0.1 / 0.0 ± 0.0 / 0.0 ± 0.0 / 0.0 ± 0.0
1 / 6.9 ± 1.3 / 4.6 ± 1.0 / 5.7 ± 1.7
5 / 30.3 ± 4.3 / 33.0 ± 1.3 / 31.7 ± 3.3
10 / 40.0 ± 0.4 / 45.3 ± 2.0 / 43.0 ± 3.2

Table OR1. Precursor conc. vs percentage yield of [18F]-Product.

Figure OR1. Precursor (NaBF4) concentration vs Percentage yield of [18F]-Product

2. Uptake and efflux of [99mTc]-pertechnetate in rat thyroid cells

Figure OR2 is provided for comparison with Fig. 3 in the published paper. Methods were as described for [18F]-TFB in Materials and methods section.

Fig. OR2 Uptake of pertechnetate in rat thyroid cells in vitro, and its inhibition by perchlorate (top), and efflux of radioactivity from cells that had previously taken up pertechnetate (bottom).

3. Comparison of ex vivo biodistribuition of [18F]-TFB and [99mTc]-pertechnetate in normal Balb/C mice

Ex vivo biodistribution measurement was carried out with Balb/C mice, n = 3. Methods were as described in Materials and Methods section.

Fig. OR3 Comparison of SUV values for [18F]-TFB and [99mTc]-pertechnetate in tissues of Balb/C mice.

Fig. OR4 Comparison of the SUV organ-to-blood ratios for TFB and pertechnetate in the same animals as Fig. OR3 above. This comparison allows a more realistic prediction of thyroid-to-background ratios in PET and SPECT images and shows that the two tracers would be very similar in this respect.