Developing agents variable contrast

The advent of the FFC instruments has opened a number of important application areas (molecular dynamics of liquid crystals, paramagnetic contrast MRI agents, proteins, polymers, etc.) and has thus provided a powerful impulse for further development of variable-field NMR relaxometry. Since 1996, Stelar entered the field and, building on the Noack-Schweikert technology (67), started producing the first commercial FFC NMR relaxometers. The availability of such instruments has further enhanced the drive towards new applications, apart from confirming the enormous potential of the technique as a primary tool for the study of molecular dynamics of even quite complex systems. 

In orthotopically transplanted murine models of brain tumors, cross-section micro-MRI at 11.7 T allows for visualization and measurement of the physically inaccessible tumors. To allow for long resident times of a contrast agent in the tumor, intraperitoneal administration was used as a route of injection for contrast-enhanced micro-MRI, and a simple method for relative tumor volume measurements was examined. A strategy for visualizing the variability of the delayed tumor enhancement was developed. These strategies were applied to monitor the growth of brain tumors xenotransplanted into nude mice and either treated with the antiangiogenic peptide EMD 121974 or an inactive control peptide. 

A variety of liver contrast agents have been developed for contrast-enhanced MR imaging of the liver, which are designed to overcome the limitations of extracellular low molecular gadolinium chelates. The two main classes of liver-specific contrast agents are the superparamagnetic iron oxide (SPIO) with uptake via the reticuloendothelial system (RES) mainly into the liver and spleen, and the hepatobiliary contrast agents with uptake into hepatocytes followed by variable biliary excretion. 

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