Use of a blood-pool contrast agent for MR-guided vascular procedures: Feasibility of ultrasmall superparamagnetic iron oxide particles

Rationale and Objectives. The purpose of this study was to examine the dose dependency of the intravascular signal intensity after injection of ultrasmall superparamagnetic iron oxide (USPIO) particles (SH U 555 C) in a rabbit model studied with a low-field-strength magnetic resonance (MR) imaging system. The results were used to facilitate MR-guided vascular procedures in a pig. Materials and Methods. All experiments were performed at 0.2 T. To determine the optimum USPIO (or SH U 555 C) dose for intravascular interventions, the authors acquired coronal three-dimensional MR angiographic images in 12 rabbits after injection of four dose levels (10, 20, 30, and 40 μmol of iron per kilogram body weight). The intraaortic signal intensities were measured in user-defined regions of interest. For numerical analysis, signal intensity enhancement was computed. Subsequently MR image-guided procedures were performed in USPIO-enhanced vessels in one pig. Results. The signal intensity evaluation shows a clear-cut dose dependence in both early and late phases after administration of SH U 555 C. A high-spatial-resolution MR angiogram acquired 20 minutes after injection yielded the best results with the highest dose (40 μmol of iron per kilogram); at that dose, intravascular enhancement was sufficient for vascular procedures for 60 minutes after injection. Conclusion. SH U 555 C is a promising contrast agent for MR angiography and MR-guided vascular procedures in an open low-field-strength MR imager.