[en] Extraction index (EI₅) was introduced to evaluate liver function quantitatively with ^99mTc-GSA (GSA) scintigraphy, and it was compared with conventional indices; receptor index (LHL₁₅) and clearance index (HH₁₅). EI₅ is expressed as the following equation: EI₅=(L₅-L₃)/(H₃+H₅)*P_H/P_L where L₃, L₅: counts at 3 or 5 minutes after the injection in the liver ROI, respectively, H₃, H₅: counts at 3 or 5 minutes in the heart ROI, respectively; P_L, P_H: numbers of pixels in the liver- and heart-ROI, respectively. We performed GSA scintigraphy in 40 patients with liver dysfunction and calculated values of the indices. Good correlations were observed between EI₅ and liver function tests. Correlation coefficients were almost equal to or higher than those between conventional parameters and liver functional tests. EI₅ was thought to be a practical index, and it could be calculated in a short time without aid of computer. Evaluation of local liver function may be possible, because EI₅ was corrected with numbers of pixels in the liver- and heart-ROI; which was not considered in the conventional parameters. (author)