Application of Superparamagnetic Iron Oxide for Hepatic Tumor Diagnosis

Abstract

Superparamagnetic iron oxide (SPIO) particles as magnetic resonance (MR) contrast media are composed of iron oxide crystals coated with dextran or carboxydextran. These particles are sequestered by phagocytic Kupffer cells in normal reticuloendothelial system (RES), but are not retained in tumor tissue. Consequently, a significant differences in T2/T2 relaxation between normal RES tissue and tumors occurs, resulting in increased lesion conspicuity and detectability. The initial introduction of SPIO was expected to substantially increase the detectability of malignant hepatic tumors. It has been documented that SPIO-enhanced MR imaging is at least as accurate as CT during arterial portography in the detection of hepatic metastases, and is slightly better diagnostic performance than dynamic helical CT in the detection of hypervascular hepatocellular carcinomas. A combination of dynamic and static MR imaging technique using T1 and T2 imaging criteria appears to provide clinically more useful enhancement patterns. T2-weighted SPIO-enhanced MR imaging also provides useful clinical information by tumor enhancement of frequent benign tumors such as hemangiomas and RES-containing tumors compared to non-uptake of fiver metastases. The possibility of one-step diagnosis is an attractive alternative to existing multi-step diagnoses in liver imaging, and is expected to be economically favorable.