Stephan Metz MD, PRESENTER: Nothing to Disclose

Abstract: HTML Purpose: To evaluate the capacity of human monocytes to phagocytose iron oxide based magnetic resonance (MR) contrast agents of different particle size, concentrations and incubation times in order to provide an optimized depiction of the labelled cells with MR imaging. Methods and Materials: Human monocytes were isolated from blood samples and incubated in vitro with superparamagnetic iron oxide particles (SPIO): Ferumoxides (Endorem, Guerbet, France and Feridex, Advanced Magnetics, USA) and Ferucarbotran (Resovist, Schering AG, Germany) as well as ultra small SPIO (USPIO): Ferumoxtran (Sinerem, Guerbet and Combidex, Advanced Magnetics) and Ferumoxtran-10 (Resovist S, Schering AG). The influence of different particles sizes (SPIO versus USPIO), varying iron oxide concentrations (5-500 μg iron/ml) and of varying incubation times (1-24 hrs) on cellular iron oxide uptake was investigated. The intracellular iron content was measured by atomic emission absorption spectrometry. In addition, MR signal intensities and T1- and T2-relaxation rates of labelled cells and non-labelled controls were determined with a clinical 1.5 Tesla MR scanner (Philips ACS Intera, The Best, Netherlands). Results: A significantly (p<0.05) higher cellular iron oxide uptake was found after incubation with SPIO compared to USPIO. The ionic SPIO Ferucarbotran revealed the highest uptake of all iron oxides. In vitro incubations of the cells with contrast agent concentrations, that exceeded those reached in plasma after intravenous injection of clinical doses, increased the cellular iron uptake significantly (p<0.05) and these differences could be depicted and quantified with MR. A maximal monocyte iron oxide uptake was achieved after an incubation time of 4 hrs and this uptake did not increase further with longer incubation periods. Conclusion: SPIO are better suited than USPIO for labelling of human monocytes. The capacity of human monocytes to phagocytose iron oxides is higher than the in vivo plasma concentration allows. Therefore, an ex vivo labelling prior to injection may improve the in vivo depiction of human monocytes with MR.       Questions about this event email: smetz@roe.med.tu-muenchen.de

Metz MD, S, Optimized Labelling of Human Monocytes with Iron Oxide MR Contrast Agents.  Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL. http://archive.rsna.org/2003/3105866.html