Automation of (64)Cu production at Turku PET Centre.

At Turku PET Centre automation for handling solid targets for the production of (64)Cu has been built. The system consists of a module for moving the target from the irradiation position into a lead transport shield and a robotic-arm assisted setup for moving the target within radiochemistry laboratory. The main motivation for designing automation arises from radiation hygiene.

64Cu- and 68Ga-labelled [Nle(14),Lys(40)(Ahx-NODAGA)NH2]-exendin-4 for pancreatic beta cell imaging in rats.

PURPOSE: Glucagon-like peptide-1 receptor (GLP-1R) is a molecular target for imaging of pancreatic beta cells. We compared the ability of [Nle(14),Lys(40)(Ahx-NODAGA-(64)Cu)NH2]-exendin-4 ([(64)Cu]NODAGA-exendin-4) and [Nle(14),Lys(40)(Ahx-NODAGA-(68)Ga)NH2]-exendin-4 ([(68)Ga]NODAGA-exendin-4) to detect native pancreatic islets in rodents. PROCEDURES: The stability, lipophilicity and affinity of the radiotracers to the GLP-1R were determined in vitro. The biodistribution of the tracers was assessed using autoradiography, ex vivo biodistribution and PET imaging. Estimates for human radiation dosimetry were calculated. RESULTS: We found GLP-1R-specific labelling of pancreatic islets. However, the pancreas could not be visualised in PET images. The highest uptake of the tracers was observed in the kidneys. Effective dose estimates for [(64)Cu]NODAGA-exendin-4 and [(68)Ga]NODAGA-exendin-4 were 0.144 and 0.012 mSv/MBq, respectively. CONCLUSION: [(64)Cu]NODAGA-exendin-4 might be more effective for labelling islets than [(68)Ga]NODAGA-exendin-4. This is probably due to the lower specific radioactivity of [(68)Ga]NODAGA-exendin-4 compared to [(64)Cu]NODAGA-exendin-4. The radiation dose in the kidneys may limit the use of [(64)Cu]NODAGA-exendin-4 as a clinical tracer.

19F/18F exchange synthesis for a novel [18F]S1P3-radiopharmaceutical.

(19)F/(18)F isotope exchange is a useful method to label drug molecules containing (19)F-fluorine with (18)F without modifying the drug molecule itself. Sphingosine-1-phosphate (S1P) is an important cellular mediator that functions by signaling through cell surface receptors. S1P is involved in several cell responses and may be related to many central nervous system disorders, including neural malfunction in Alzheimer's disease. In this study, [(18)F]1-benzyl-N-(3,4-difluorobenzyl)-2-isopropyl-6-(2-methoxyethoxy)-1H-indole-3-carboxamide, a novel (18)F-labeled positron emission tomography tracer for the S1P3 receptor, was successfully synthesized using the (19)F/(18)F isotope exchange reaction. Parameters of the reaction kinetics were studied, and correlations between the initial (18)F-activity, the amount of precursor, radiochemical yield and specific activity (SA) were determined. Contrary to expectations, high initial (18)F-activity decreased the radiochemical yield, and only a minor increase of SA occurred. This is most probably due to the complexity of the molecule and the subsequent susceptibility to radiolytic bond disruption. On the basis of the present results, a convenient condition for the (19)F/(18)F exchange reaction is the use of 2 µmol precursor with 20 GBq of (18)F-activity. This afforded a radiochemical yield of ~10% with an SA of 0.3 GBq/µmol. Results from this study are of interest for new tracer development where high initial (18)F-activity and (19)F/(18)F isotope exchange is used.