Ultrastructural localization of Thorotrast (thorium dioxide) in human liver by analytical scanning electron...

The distribution of thorium dioxide (Thorotrast) in the liver from a Thorotrast-administered autopsy case was examined stereographically by analytical scanning electron microscopy. Thorium particles were detected in the macrophages of the portal triad and hepatic sinusoid. These macrophages were irregularly shaped and tended to be aggregated. In the sinusoid, accumulation of the macrophages formed a thrombus-like structure. Furthermore, observed in the sinusoid were free Thorotrast particles that appeared to have been released into the sinusoid as a result of breakdown of the macrophages (Kupffer cells).