Automated synthesis and preliminary evaluation of [¹⁸F]FDPA for cardiac inflammation imaging in rats after myocardial infarction

A translocator protein 18 kDa targeted radiotracer, N,N-diethyl-2-(2-(4-[F-18]fluorophenyl)-5,7-dimethylpyrazolo[1,5-a] pyrimidin-3-yl) acetamide ([F-18]FDPA), was automated synthetized and evaluated for cardiac inflammation imaging. Various reaction conditions for an automated synthesis were systematically optimized. MicroPET/CT imaging were performed on normal rats and rats with myocardial infarction (MI). Normalized SUV ratios of [F-18]FDPA to [N-13]NH3 (NSRs) in different regions were calculated to normalize the uptake of [F-18]FDPA to perfusion. The amount of TBAOMs and the volume/proportion of water were crucial for synthesis. After optimization, the total synthesis time was 68 min. The non-decay corrected radiochemical yields (RCYs) and molar activities were 19.9 +/- 1.7% and 169.7 +/- 46.5 GBq/mu mol, respectively. In normal rats, [F-18]FDPA showed a high and stable cardiac uptake and fast clearance from other organs. In MI rats, NSRs in the peri-infarct and infarct regions, which were infiltrated with massive inflammatory cells revealed by pathology, were higher than that in the remote region (1.20 +/- 0.01 and 1.08 +/- 0.10 vs. 0.89 +/- 0.05, respectively). [F-18]FDPA was automated synthesized with high RCYs and molar activities. It showed a high uptake in inflammation regions and offered a wide time window for cardiac imaging, indicating it could be a potential cardiac inflammation imaging agent.