Quantitative evaluation of liver function with 99mTc-GSA scintigraphy using extraction index

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)*PH/PL 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; PL, PH: 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)