New Aspects of Biodistribution of Perfluorocarbon Emulsions in Rats: Thymus Imaging

MRI on fluorine-19 is an effective tool for imaging and monitoring phagocytic cells (macrophages, stem cells, etc.) This method is based on the visualization of perfluorocarbon (PFC) emulsions, which nanoparticles undergo endocytosis by macrophages in an organism. The liver and spleen are main places of emulsion accumulation, but not the only ones. The purpose of our study was to identify organs (besides the liver and spleen) that can accumulate PFC emulsions sufficiently for 19F MRI. We studied the biodistribution of PFC emulsion in rats after two different methods of its introduction into an organism (intravenously and intraperitoneally). It was shown that PFC emulsions are accumulated by the thymus and the nearest lymph nodes in the sufficient amount (around 2% of the total intraperitoneally injected dose) to be visualized. It turned out that PFC emulsion is accumulated more in thymus after intraperitoneal injection in comparison with intravenous injection. This is due to the differences in the capture of emulsion by macrophages when it is initially injected into the bloodstream or the abdomen.