To explore the biodistribution and quantitative value of ¹⁸F-Flurpiridaz in mini-swine, and compare with ¹³N-NH₃·H₂O.

Ten Bama mini-swine were divided into normal group and myocardial infarction group (n=5 in each group). Normal group was not treated and myocardial infarction group was modeled by thoracotomy and coronary artery ligation. Both groups were preceded by ¹³N-NH₃·H₂O imaging, followed by ¹⁸F-Flurpiridaz imaging (time interval >40 min). Injection dosage of 2 tracers was the same (185-370 MBq). ¹⁸F-Flurpiridaz whole-body PET/CT imaging was also performed in normal group. Biological distribution of ¹⁸F-Flurpiridaz was observed, and the ratio of radioactive uptake of ¹⁸F-Flurpiridaz between myocardium and adjacent tissues or organs was calculated. Image quality score and rest myocardial blood flow (rMBF) of 2 imaging tracers in normal group were measured and compared. MPI image quality score, cardiac function parameters such as summed rest score (SRS), myocardial infarction area percentage, total perfusion defect (TPD), and left ventricular ejection fraction (LVEF) of 2 imaging tracers were compared in myocardial infarction group. Data was analyzed by paired t test.

In normal group, ¹⁸F-Flurpiridaz in the myocardium was clearly observed, with high radioactive uptake maintaining within 2 h postinjection. The radioactivity count ratios of left ventricular myocardium to cardiac pool, the lungs and liver were high (5.19-12.87, 4.17-50.51, 2.08-6.92). The quality of ¹⁸F-Flurpiridaz MPI images in both groups was excellent (10/10). The rMBF (ml·g^-1·min^-1) in different regions of left ventricle measured by ¹⁸F-Flurpiridaz and ¹³N-NH₃·H₂O imaging were not significantly different (left anterior descending: 0.98±0.06 vs 0.92±0.13; left circumflex: 0.98±0.05 vs 0.88±0.12; right coronary artery: 0.95±0.07 vs 0.88±0.15; left ventricle: 0.96±0.07 vs 0.90±0.13; t values: from -1.70 to -0.90, all P>0.05). There was no significant difference in SRS, myocardial infarction area percentage, TPD, rMBF or LVEF between¹⁸F-Flurpiridaz and ¹³N-NH₃·H₂O (SRS: 10.6±4.1 vs 9.2±4.6; myocardial infarction area percentage: (15.2±9.0)% vs (12.6±6.6)%; TPD: (11.6±6.3)% vs (9.6±3.9)%; LVEF: (68.6±11.1)% vs (71.4±11.3)%; t values: -2.33-2.75, all P>0.05).

Comparing with ¹³N-NH₃·H₂O, ¹⁸F-Flurpiridaz has the advantages of good MPI image quality, accurate measurement of cardiac function parameters and quantitative potential of myocardial blood flow, which make it as a promising positron myocardial perfusion imaging agent.

Myocardial perfusion imaging; Pyridazines; Fluorine radioisotopes; Ammonia; Positron-emission tomography; Tomography, X-ray computed; Swine