[Estimation of 99mTc-GSA receptor amount by non-linear 3-compartment model: ligand-receptor binding model without blood sampling].

99mTc-GSA (galactosyl serum albumin) receptor amount (Ro) was estimated by a non-linear 3-compartment model of the ligand-receptor binding without blood sampling. Forward/reverse rate constants and receptor amount were assumed to be variable. Relationship between this parameter and other conventional parameters including ICG R15 (15-minutes retention rate of indocyanine green) was evaluated for 43 surgical candidates with liver tumors. Linear relationships between Ro and HH15 and LHL15 were R2 = 0.73 and 0.72, respectively. Linear relationship between Ro and Rmax, the maximum removal rate, is also good (R2 = 0.84), and the regression line (y = 0.038x + 0.066) was slightly over 0 at y-interception. Linear relationship between Ro and ICG R15, was poor (R2 = 0.39) and relationship was rather a concave shape. Linear relationship of reduction rate between Ro and non-tumor tissue volume of the liver, which assessed at the same day of two weeks after the operation, was y = 1.09x - 0.01 (R2 = 0.82). GSA receptor amount, Ro, seems to change proportional to non-tumor liver tissue volume changing before and after hepatectomy. Complementary to ICG R15, it may be an useful and intuitive parameter for hepatectomy.