Monocyte imaging after myocardial infarction with 19F MRI at 3 T: a pilot study in explanted porcine hearts

Aim Inflammation is a hallmark of cardiac healing after myocardial infarction and it determines subsequent cardiovascular morbidity and mortality. The aim of the present study was to explore whether inflammation imaging with two perfluorocarbon (PFC) nanoemulsions and fluorine magnetic resonance imaging (F-19 MRI) is feasible at 3.0 T with sufficient signal-to-noise ratio (SNR) using explanted hearts, an 19F surface coil and dedicated MR sequences. Methods and results Acute myocardial infarction (AMI) was induced by balloon angioplasty (50 min) of the distal left anterior descending artery in 12 pigs. One day thereafter, PFCs were injected intravenously to label circulating monocytes. Either emulsified perfluoro-15-crown-5ether or already clinically applied perfluorooctyl bromide (PFOB) was applied. Four days after AMI and immediately after gadolinium administration, hearts were explanted and imaged with a 3.0 T Achieva MRI scanner. 19F MRI could be acquired with an SNR of > 15 using an in-plane resolution of 2 x 2 mm(2) within,20 min for both agents. Combined late gadolinium enhancement (LGE) and 19F MRI revealed that 19F signal was inhomogenously distributed across LGE myocardium reflecting patchy macrophage infiltration as confirmed by histology. In whole hearts, we found an apico-basal 19F gradient within LGE-positive myocardium. The F-19-positive volume was always smaller than LGE volume. Ex vivo experiments on isolated monocytes revealed that pig and human cells phagocytize PFCs even more avidly than mouse monocytes. Conclusion This pilot study demonstrates that 19F MRI at 3.0 T with clinically applicable PFOB is feasible, thus highlighting the potential of 19F MRI to monitor the inflammatory response after AMI.