Tc-NGA imaging in liver transplantation: preclinical studies

Tc-99m galactosyl-neoglycoalbumin (Tc-NGA) is a new liver-imaging agent which binds to hepatic binding protein (an hepatocyte-specific membrane receptor). This study evaluated the sensitivity of Tc-NGA kinetics and imaging anatomy to pathologic states that are encountered after liver transplantation. Studies were performed in adolescent pigs under control conditions (18 studies), and after orthotopic liver transplantation (nine studies), common bile duct ligation (three studies), hepatic artery ligation (one study), and hepatic resection (two studies). Anatomic and kinetic data were analyzed. Excellent liver images and minimal kinetic changes were noted after common bile duct ligation. Marked imaging defects and major kinetic alterations were observed after hepatic artery ligation and in the presence of preservation injury. Marked depression in hepatic Tc-NGA uptake was observed during acute rejection. Minor alterations in Tc-NGA kinetics were noted after a 25% hepatectomy. These studies indicate that minimal changes in Tc-NGA uptake occur after common bile duct ligation; Tc-NGA uptake is markedly sensitive to hepatic ischemia; decreased Tc-NGA uptake occurs during acute rejection; and hepatic infarcts are demonstrated promptly after preservation injury. Thus Tc-NGA imaging provides a novel means of evaluating hepatic ischemia, hepatic preservation, and hepatic allograft rejection. Tc-NGA imaging may also provide a means of evaluating hepatic regeneration and hepatocyte retrodifferentiation during regeneration.