Ultrasmall particulate iron oxides as contrast agents for magnetic resonance spectroscopy: A dose-effect study

Long-distance effects of a superparamagnetic contrast agent (AMI227) were i nvestigated by phosphorus-31 NMR spectroscopy at 7.05 Tesla. In an Initial methodological approach, the effects observed on phantoms were compared to the results of theoretical calculations. In a second step, the particles we re administered to excised and perfused rat livers (N = 5) and hearts (N = 5) through the perfusion medium for 12 minutes at various concentrations (0 .9, 1.8, and 3.6 mM Fe). Organs were subsequently rinsed with the perfusion medium for 42 minutes. During particle perfusion, the spectral lines were shifted and exhibited a strong broadening, although the peak area remained constant, testifying to the inocuity of the material. For hearts only, thes e disturbances disappeared upon organ rinsing. These through-space suscepti bility effects of the particles located In the vessels on phosphorus nuclei , which are strictly confined to the Intracellular space, show that high-su sceptibility intravascular agents could be useful to evaluate tissue perfus ion by contrast-enhanced spectroscopy. (C) 2001 Wiley-Liss, Inc.