Clinical utility of receptor imaging in the assessment of liver function

Technetium-99m diethylene triamine pentaacetic acid-galactosyl human serum albumin (TcGSA) is a newly developed receptor-binding radiopharmaceutical, specific for the asialogycoprotein receptor, which resides exclusively on the plasma membrane of hepatocytes. Clinical utility of TcGSA was evaluated in 3 control subjects with normal livers and in 54 patients with various liver diseases. The parameter, Receptor Index, was derived from liver and heart time-activity data and is the ratio of radioactivity of the liver over the radioactivity of the liver plus heart at 15min after the intravenous injection of 3mg of TcGSA. Receptor concentration ([R]o) was obtained by kinetic analysis of liver and heart time-activity data using pharmacokinetic nonlinear modeling. Values for the Receptor Index and [R]o were statistically different in the control subjects and in patients with mild, moderate, and severeliver diseases. Good correlations were obtained between the Receptor Index, [R]o and conventional liverfunction tests, such as Child-Turcotte criteria score, prothrombin time, and indocyanine green test. Receptor Index and [R]o were properly estimated even in patients with obstructive jaundice or remarkable portocaval shunt. These data suggest that the receptor imaging as well as its parameters, Receptor Index and [R]o, is a potentially practical and reliable diagnostic method for estimating the functioning hepatocyte mass and for assessing liver function.