Biodistribution and radiation dosimetry in humans of a new PET ligand, ¹⁸F-PBR06, to image translocator protein (18 kDa)

As a PET biomarker for inflammation, translocator protein (18 kDa) (TSPO) can be measured with an ¹⁸F-labeled aryloxyanilide, ¹⁸F-N-fluoroacetyl-N-(2,5-dimethoxybenzyl)-2-phenoxyaniline ( ¹⁸F-PBR06), in the human brain. The objective of this study was to estimate the radiation absorbed doses of ¹⁸F-PBR06 based on biodistribution data in humans. Methods: After the injection of ¹⁸F-PBR06, images were acquired from head to thigh in 7 healthy humans. Urine was collected at various time points. Radiation absorbed doses were estimated by the MIRD scheme. Results: Moderate to high levels of radioactivity were observed in organs with high densities of TSPO and in organs of metabolism and excretion. Bone had low levels of radioactivity. The effective dose was 18.5 μSv/MBq. Conclusion: The effective dose of ¹⁸F-PBR06, compared with other ¹⁸F radioligands, was moderate. This radioligand had negligible defluorination, as indirectly assessed by bone radioactivity. Doses to the gallbladder wall and spleen may limit the amount of permissible injected radioactivity.