Analysis of the early blood kinetics of 99mTc-GSA and its verification: new one-compartment model and regression equation.
Technetium-99m-galactosyl human serum albumin (99mTc-GSA) is a radiopharmaceutical that binds to asialoglycoprotein receptors in the hepatocyte membrane; the level of 99mTc-GSA accumulation in the liver correlates well with the parameters of hepatic function tests. We hypothesized that the early blood kinetics of 99mTc-GSA could be described by a simple one-compartment model expressed as an offset + a monoexponential function (y=y0 +Ae(-alpha)t). The aims of this study were to assess the validity of this hypothesis using sequentially measured blood levels of 99mTc-GSA, which were approximated by a regression expression, and to analyse the regression equation. 99mTc-GSA levels were measured in blood samples collected from 30 patients with liver disease. From sequential changes in radioactivity up to 30 min after injection, a regression equation expressed as an offset+ a monoexponential function was calculated and evaluated by multiple correlation coefficients and absolute deviations (% error). The liver uptake rate 15 min after injection of 99mTc-GSA (liver uptake rate 15, UTR 15) was calculated from the regression equation in each case. The respective relationships of this parameter to the coefficient [A] and gradient [alpha] were evaluated. In all cases, the measured values of radioactivity in blood samples could be fitted to an offset + a monoexponential function. The validity of our hypothesis was supported by examining regression equations calculated from blood 99mTc-GSA levels. Analysis of the regression equations suggested a potential for a new index of hepatic functional reserve.
Sugai
Y
Y
Department of Radiology, Yamagata University School of Medicine, Japan. ysugai@med.id.yamagata-u.ac.jp
Komatani
A
A
Hosoya
T
T
Takahashi
K
K
D000465:Algorithms; D005260:Female; D006505:Hepatitis / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012044:Regression Analysis; D013668:Technetium Tc 99m Aggregated Albumin / Q000493:pharmacokinetics*; D016284:Technetium Tc 99m Pentetate / Q000493:pharmacokinetics*
D019275:Radiopharmaceuticals; D013668:Technetium Tc 99m Aggregated Albumin; C070561:technetium Tc 99m DTPA-galactosyl-human serum albumin; D016284:Technetium Tc 99m Pentetate