Evaluation of heart time-activity curves as a predictor of hepatic extraction of Tc-99m-mebrofenin in dogs

In this study, heart time-activity curve, created following intravenous inj ection of Tc-99m-mebrofenin were used to quantify hepatic function in norma l dogs and dogs with induced hepatic parenchymal cell damage. The results w ere compared to a direct measurement of hepatic extraction following mesent eric venous injection of Tc-99m-mebrofenin. The heart time-activity curves were normalized and the area under the curve from 0-30 minutes and 0-60 min utes were determined, In addition, the half-time clearance rate of the hear t time-activity curve aas analyzed using a two-compartment model, Linear re gression analysis nas used to describe the relationship between the area un der the normalized heart time-activity curve and hepatic extraction. There was good correlation between the area under the normalized heart time-activ ity. curve and hepatic extraction. The best correlation was obtained from t he 0-30 minute data (r(2) = 0.92), A formula for calculating hepatic extrac tion was derived using linear regression analysis: Hepatic extraction = 1.0 92 - (0.0000308 x AUC(0-30 minutes)). There was good correlation between th e half-time clearance rates from the heart time-activity curve and hepatic extraction. The best correlation was between the fast phase half-time clear ance and hepatic extraction (r(2) = 0.88), The area under a normalized hear t time-activity curve can be used as a simple alternative to deconvolutiona l analysis for the determination of hepatic extraction as a measure of hepa tic parenchymal cell function in the dog.