Application of superparamagnetic iron oxide to imaging of hepatocellular carcinoma

Superparamagnetic iron oxide (SPIO) particles are as MR contrast media 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, there are significant differences in T2/T2* relaxation between normal RES tissue and tumors, which result in increased lesion conspicuity and detectability. The introduction of SPIO has been expected to substantially increase the detectability of hepatic metastases. For focal hepatocellular lesions, it has been documented that SPIO-enhanced MR imaging exhibits slightly better diagnostic performance than dynamic helical CT in the detection of hypervascular hepatocellular carcinoma (HCC). A combination of dynamic and static MR imaging technique using T1- and T2 imaging criteria appears to provide clinically more useful patterns of enhancement. SPIO-enhanced MR imaging also provides information useful for differential diagnosis, via enhancement of RES-containing tumors. With the exploitation of rapid T2*-sensitive sequences, SPIO-enhanced dynamic MR imaging may become comparable to gadolinium-enhanced dynamic MR imaging and dynamic studies with multidetector-row CT. SPIO-enhanced MR imaging plays an important role in therapeutic decision-making for patients with HCC.