Objective To investigate the automated synthesis of ¹⁸F-meta-fluorobenzylguanidine (MFBG) and its application in cardiac sympathetic nerve imaging in healthy beagle dogs, and the in vivo distribution of this imaging agent.

Methods The automated synthesis method was established using a positron-emitting drug synthesis module. A self-controlled design was adopted. Three healthy beagle dogs, 2 males and 1 female, aged 13−15 months and weighing approximately 15 kg, were used. In the ¹⁸F-MFBG in vivo distribution study, dynamic whole-body PET/CT imaging was performed on experimental dogs to observe the characteristics of the distribution of ¹⁸F-MFBG in major organs over time, as well as the changes in the radioactive count ratios of the left ventricular myocardium to the blood pool, liver, lungs, spleen, and kidneys over time, in order to determine the optimal cardiac imaging time.

Results ¹⁸F-MFBG was successfully synthesized automatically in five consecutive runs, with the synthesis time of (75±11) min and the synthesis yield of (18.2±2.6) %. In the experimental dogs, ¹⁸F-MFBG provided clear myocardial imaging, with an image quality score of excellent (4 points). The imaging agent was distributed uniformly across myocardial segments, exhibiting low radioactive counts in the cardiac chambers and no extracardiac radioactive interference. The left ventricular myocardium was clearly visualized as early as 10 min post-injection and maintained high radioactive uptake for 2 h. At 60 min, the maximum mean value of the radioactive count ratio of the left ventricular myocardium to the lungs was 7.31. At 90 min, the maximum mean value of the radioactive count ratio of the left ventricular myocardium to the blood pool was 12.93. The optimal cardiac imaging time in experimental dogs was 60−90 min after injection.

Conclusions The automated synthesis of ¹⁸F-MFBG was achieved. ¹⁸F-MFBG cardiac sympathetic nerve imaging in experimental dogs showed clear images, with no obvious extracardiac radioactive interference. Thus, it is a promising positron-emitting agent for cardiac sympathetic nerve imaging.