¹⁹F magnetic resonance imaging of the reticuloendothelial system

Abstract

In this study sequential 1H and 19F magnetic resonance imaging methods were used to map the distribution of fluorinated compounds in vivo. An intravenously administered emulsion of perfluorooctylbromide (PFOB), an agent known to localize in the reticuloendothelial system, was detected in the liver and spleen of all studied hamsters and mice using 19F MRI. Lungs and salivary glands were also affected in some animals. Using a G. E. NMR CSI 2-T spectroscopy/imaging system, projection 19F images were obtained in 4 to 8 min. Subsequent mouse studies using a thick-slice driven equilibrium pulse sequence produced 19F images with an improved signal-to-noise ratio in a shorter acquisition time. With PFOB, 19F MRI has the capability of detecting macrophages in the reticulo-endothelial system and in other sites where macrophages congregate. This is the first report where the reticuloendothelial system was specifically imaged in live animals and where driven equilibrium imaging techniques have been applied to 19F MRI.

Tissue oxygenation: A novel determination using 19F surface coil NMR spectroscopy of sequestered perfluorocarbon emulsion

“…19F MRI investigations have examined pOz in vivo in the reticuloendothelial system (liver and spleen) ( 12, 19, lungs (13), and brain (14). The liver and spleen are the preferred sites for these studies because oftheir high vascularity and the tendency of the perfluorocarbon emulsions to accumulate in these organs ( 16,17,25). Concentrations of perfluorocarbons in other organs and tissues are much lower ( 16,17,26), leading to poor SIN and excessive imaging times, e.g., 1 h (14).…”

In situ assessment of tumor vascularity using fluorine nmr imaging

“…The evidence presented here and throughout the literature demonstrates that the perfluorocarbon blood substitute emulsions remain primarily in the blood up to several hours following iv administration ( 1 7,19,21,22). Over days to weeks following administration the perfluorocarbons accumulate into the reticuloendothelial system and into macrophages ( 17,(21)(22)(23). There is some evidence that perfluorocarbons accumulate into tumor tissue at several days after administration ( 16).…”

A new perfluorocarbon for use in fluorine‐19 magnetic resonance imaging and spectroscopy

“…The advent of PFC emulsions as artificial blood substitutes has stimulated the 19F MRI investigation of these compounds for imaging the vascular system and large blood pools in the heart and brain (1-4). The uptake of large concentrations of PFCs by the reticuloendothelial system (RFS) of the liver and spleen has made 19F MRI an ideal tool for studying the biodis-tribution of PFCs in these organs (5,6). Macrophages in abscesses and tumors can also sequester PFCs and 19F MRI of such PFC "contrast agents" can potentially be used to disclose these lesions (7)(8)(9).…”

“…Attempts to mitigate the long PFC T, relaxation times have generally involved the use of driven-equilibrium pulse sequence methods (5). Reducing T2 signal loss when imaging PFCs usually requires MRI instrumentation with relatively strong, rapidly switching gradients to achieve the minimum possible echo time (TE) for spin-echo (SE) imaging.…”