Lipid Soluble Contrast Agents for Computed Tomography of the Liver

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Abstract
A new class of compounds, polyiodinated sterol esters, was recently synthesized and has characteristics suggesting potential value as site-specific hepatic computed tomographic (CT) contrast agents. A prototype compound, cholesteryl iopanoate, was administered i.v. to rabbits in doses of 65 mg I/kg. The compound significantly enhanced hepatic parenchyma to a maximal level of 65 Hounsfield units (HU) above base-line values without observable splenic enhancement. A subsequent study comparing the administered dose with the change in CT attenuation values of liver demonstrated that near-maximum enhancement reaching 22 HU was achieved at a dose of 30 mg I/kg within 24 h after injection. The enhancement characteristics suggest the mechanism of the hepatic accumulation may not be mediated solely by the RES. Administration of cholesteryl iopanoate (30 mg I/kg) to rabbits with hepatic tumors (V .times. 2 adenocarcinoma) resulted in the CT imaging of tumors as small as 2 mm in diameter. Further investigation of this new class of lipid-soluble contrast agents seems warranted.