Ferrite particles: a superparamagnetic MR contrast agent for enhanced detection of liver carcinoma.

The potential of superparamagnetic ferrite particles to enhance detection of liver carcinoma at magnetic resonance (MR) imaging was studied with in vitro MR spectroscopy and in vivo MR imaging in animal models. After intravenous administration of ferrite, MR spectroscopy showed selective shortening of T2 relaxation times in normal liver but not in tumor. MR imaging showed that ferrite produced profound signal loss only from normal liver and not tumor; thus, differences in signal intensity between liver and tumor were greatly enhanced, especially on pulse sequences with T2-dependent contrast. Motion artifacts were reduced as well because of less signal from liver. Microscopic analysis showed sequestration of ferrite particles in hepatic reticuloendothelial cells but not in hepatocytes or tumor tissue, and there was no evidence of cellular injury. Ferrite particles efficiently and predictably enhance signal differences between normal liver and tumor and permit considerable latitude in selection of pulse sequence and timing parameters. Thus, they have considerable promise as a tissue-specific MR contrast agent for improved detection of liver carcinoma.