Whole Body PET Imaging with a Norepinephrine Transporter Probe 4-[¹⁸F]Fluorobenzylguanidine: Biodistribution and Radiation Dosimetry

4-[¹⁸F]Fluorobenzylguanidine ([¹⁸F]PFBG) is a positron emission tomography (PET) probe for non-invasive targeting of the norepinephrine transporter. The aim of this study was to assess uptake and distribution characteristics of this PET probe.

Three cynomolgus monkeys were injected with 269 ± 51 MBq (7.3 ± 1.4 mCi) of [¹⁸F]PFBG and 21 whole body PET scans were acquired over 165 min. s around organs to generate time-activity curves. The absorbed doses to individual organs and the effective dose to the whole body were estimated.

Favorable distribution of [¹⁸F]PFBG was noted with a fast wash-in and wash-out of radioactivity from several tissues. [¹⁸F]PFBG rapidly distributed in the heart, liver, kidneys, and adrenal glands. The uptake presented as %ID in the brain, lung, and spleen was 1.06 ± 0.45, 6.28 ± 0.33, and 1.39 ± 0.35 at 1 min and decreased to 0.29 ± 0.02, 1.78 ± 0.31, and 0.66 ± 0.22 by 112 min. In general, a two- to fourfold reduction was noted from peak radioactivity levels. Rapid uptake and significant retention of radioactivity was noted in the heart and the septal wall was distinctly visible by 20 min. Fast wash-in and washout kinetics for [¹⁸F]PFBG resulted in shorter residence times. The residence time for the liver, lungs, kidneys, and spleen were 28.01 ± 7.73 min, 2.97 ± 0.56 min, 6.04 ± 3.41 min, and 1.09 ± 0.33 min, respectively. The mean effective dose for the 70-kg male was 0.04 ± 0.00 mSv/MBq. The organs receiving the highest radiation dose in the 70-kg male model were the testes (0.11 ± 0.02 mGy/MBq), adrenals (0.08 ± 0.01 mGy/MBq), and urinary bladder wall (0.08 ± 0.01 mGy/MBq).

[¹⁸F]PFBG shows a favorable biodistribution pattern. Rapid and persistent uptake was noted in innervated organs. Renal clearance was the major path for elimination of [¹⁸F]PFBG. The estimated radiation burden from [¹⁸F]PFBG was significantly lower than that from [¹²⁴I]MIBG.