Contrast enhancement in experimental radiation-induced liver injury: comparison of hepatocellular and reticuloendothelial particulate contrast agents.

We compared the liver enhancement of two superparamagnetic agents, polycrystalline iron oxide nanoparticles (PION) and PION coated with asialofetuin (ASF), in an experimental model of focal radiation-induced hepatitis. PION, a reticuloendothelial system-directed agent, and PION-ASF, a hepatocellular-directed agent, were compared for time-dependent liver enhancement in an experimental model of radiation-induced liver injury. Using the reticuloendothelial system (RES)-directed PION, the normal, nonirradiated portion of the liver decreased in signal intensity (SI) with a mean negative enhancement of -66% +/- 4, whereas the irradiated portion (60 Gy, 3 days before imaging) of the liver decreased in SI by -24% +/- 2, significantly less (P <.05). SI changes in irradiated liver tissue using PION were dose-dependent, being more pronounced with lower radiation exposure. The difference in SI changes induced by PION-ASF between irradiated and nonirradiated liver was not statistically different, but SI decreased with a mean negative enhancement of -80% +/- 2. The RES-directed PION is more sensitive for the detection of radiation-induced hepatitis than is the hepatocyte-directed PION-ASF. The insensitivity of PION-ASF enhancement for diffuse liver injury may be clinically advantageous for detecting focal lesions in the presence of diffuse hepatic injury.