Superparamagnetische Eisenoxidpartikel: Aktueller Stand und zukünftige Entwicklungen

Zusammenfassung

Für Superparamagnetische Eisenoxidpartikel (SPIO) ist in den letzten 15 Jahren ein weites Anwendungsspektrum als Kontrastmittel für die MRT aufgezeigt worden. SPIO können mit verschiedenen Partikelgrößen und Oberflächenbeschichtungen hergestellt werden. SPIO mit größeren Partikeldurchmessern (50 - 150 nm) bewirken überwiegend eine Signalminderung bzw. T₂-Verkürzung, werden als Kontrastmittel in der MRT von Leber und Milz eingesetzt und führen zu einer hohen Genauigkeit vor allem im Nachweis von Lebermetastasen (zugelassene Substanzen: AMI-25 (Endorem bzw. Ferridex), SHU-555A (Resovist)). Kleinere Partikel (ca. 20 nm Durchmesser) zeigen eine andere Organverteilung und haben das Potenzial, die nicht-invasive Lymphknotendiagnostik zu verbessern oder vulnerable atherosklerotische Plaques zu charakterisieren (in der klinischen Prüfung: AMI-227 [Sinerem bzw. Combidex]). Partikel mit optimierter T₁-Relaxivität und verlängerter intravasaler Zirkulationszeit sind als Blutpool-Kontrastmittel für die MR-Angiographie einsetzbar. Als Indikationen werden derzeit die MR-Angiographie des Körperstamms, peripherer Arterien und der Koronararterien geprüft (z. B. SHU 555 C (Supravist), VSOP-C184). Weitere derzeit in der Prüfung befindliche Indikationen kleiner SPIO sind die MRT des Knochenmarks sowie die Bestimmung von Parametern der Perfusion von Tumoren oder z. B. des Myokards. Eine entsprechende Modifikation der Partikelhülle ermöglicht Ansätze der sogenannten Molekularen Bildgebung, z. B. Rezeptor-gerichtete Bildgebung, Markierung von Zellen zum in-vivo Monitoring der Zellmigration, z. B. von Stammzellen, Markierung von Genkonstrukten zur Lokalisationskontrolle in der Gentherapie. In der Tumortherapie können SPIO als Vermittler für die Hyperthermie eingesetzt werden. SPIO stellen ein wirkungsvolles MR-Kontrastmittel mit vielseitigen Einsatzmöglichkeiten in der Bildgebenden Diagnostik bis hin zur Molekularen Medizin dar.

Abstract

A wide range of applications for superparamagnetic iron oxide (SPIO) particles as contrast media for MRI has emerged over the last 15 years. SPIO particles can be manufactured with different particle sizes and surface coatings. Large SPIO particles (50 - 150 nm) predominantly produce a signal decrease or T₂-shortening and are used as contrast media for MRI of the liver and spleen. They have a high accuracy, especially in detecting liver metastases (approved for clinical use: AMI-25 (Endorem or Ferridex), SHU-555A (Resovist)). Smaller particles (about 20 nm in diameter) show a different organ distribution and have a potential for improving noninvasive lymph node assessment or characterizing vulnerable atherosclerotic plaques (in clinical trials: AMI-227 [Sinerem or Combidex]). Particles with an optimized T₁-relaxivity and prolonged intravascular circulation time can be used as blood pool contrast media for MR angiography. The currently investigated indications are MR angiography of the trunk, peripheral vessels, and coronary arteries (e.g., SHU-555 C (Supravist), VSOP-C 184). Other applications of small SPIO particles include MRI of the bone marrow and the determination of perfusion parameters in tumors or other tissues like the myocardium. SPIO particles with a modified coat can be used in so-called molecular imaging, such as receptor-directed imaging, cell labeling for in-vivo monitoring of cell migration, e.g., stem cell labeling, and labeling of gene constructs for localization in genetic therapy. In tumor therapy SPIO particles can serve as mediators for hyperthermia. SPIO is a powerful MR contrast medium with manifold applications ranging from diagnostic imaging to molecular medicine.

Magnetic resonance imaging - MRI - contrast medium - iron oxide particles - superparamagnetism

Literatur

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