HEPATIC EXTRACTION EFFICIENCY AND EXCRETION RATE OF TECHNETIUM-99M-MEBROFENIN IN DOGS

Quantitative hepatobiliary scintigraphy aids in the diagnosis of hepat ic disease. Two scintigraphic parameters that have great value in disc riminating between hepatocellular and biliary disease are hepatic extr action fraction (HEF), which is a measure of the hepatic extraction ef ficiency (HEE), and hepatic excretion rate. It is generally accepted t hat hepatic extraction fraction is normally 100%, but a review of the literature provided little information on the actual HEF of Tc-99m-meb rofenin. Methods: We determined the HEE of Tc-99m-mebrofenin in nine n ormal dogs after direct injection into the afferent hepatic vasculatur e using a two-compartment model. The forward and reverse rate constant s for the two-compartment model were solved by a simple graphic approa ch and a more complex numerical approach using a nonlinear least squar es algorthm. The HEEs were determined using both methods. Results: The HEE for the graphic and numerical methods of analysis were not signif icantly different and were calculated to be 92.2 +/- 4.75% (mean +/- s .d.) and 91.2 +/- 4.44% (mean +/- s.d.) by each method, respectively. The half-time clearance of Tc-99m-mebrofenin was 19.10 +/- 4.86 min (m ean +/- s.d.). Conclusion: This study validates the assumption that th e normal HEE of Tc-99m-mebrofenin is nearly 100%, barring species diff erences.