On the interpretation of the early part of the liver time-activity curve: double tracer experiment.

A double tracer experiment was performed in one normal subject and in one cirrhotic patient to better understand the tracer kinetics in the liver area during the first minute after injection. From a comparison of the time-activity curves obtained in each subject by subsequent iv administration of a nonextracted and an extracted (colloidal) tracer it was possible to distinguish the contribution due to the transport mechanism through intrahepatic and extrahepatic circulation and that due to reticuloendothelial extraction. Three main phases were identified on the curves and an attempt was made to interpret their significance. Results of the study may be of interest for the development of models which could possibly provide more reliable noninvasive quantitation of liver hemodynamics and reticuloendothelial function with the use of one or both types of tracer.