Supplementary Material for: Usefulness of Liver Uptake Rate Constant in ^99mTc-GSA Scintigraphy for the Risk Stratification of Patients Undergoing Hepatectomy: A New Method for Calculation

<b><i>Introduction:</i></b> The use of technetium 99m diethylenetriaminepentaacetic acid-galactosyl human serum albumin (^99mTc-GSA) scintigraphy parameters, HH15 and LHL15, in assessing the future liver remnant function is not expedient because of their nonlinear behaviour against liver volume. Uptake rate constant for the binding of ^99mTc-GSA to asialoglycoprotein receptors is probably more favourable, but the reported calculation methods are complex. We devised a simple method to calculate the uptake rate constant, K<i>r</i>GSA. <b><i>Methods:</i></b> Radioactivity counts for the entire liver and heart regions were extracted at 10, 20, and 30 min. Using whole liver and heart volumes measured from single-photon emission computed tomography images, free radioactivity corresponding to the liver blood pool was subtracted. The time activity curve was fitted to the equation <i>L</i>(<i>t</i>) = <i>L</i>(∞) × [1 − Exp (−<i>kt</i>)] using Microsoft Office Excel (add-in free programme Solver)®, where <i>L</i>(∞) is the count at plateau level and <i>k</i> denotes K<i>r</i>GSA. <b><i>Results:</i></b> K<i>r</i>GSA values accurately identified liver cirrhosis and were similar to the KICG. The areas under the curve for K<i>r</i>GSA and KICG in the receiver operating characteristic analysis were 0.808 and 0.795, respectively, and a good correlation was seen between K<i>r</i>GSA and KICG. <b><i>Discussion/Conclusion:</i></b> K<i>r</i>GSA can be utilized as an alternative to KICG in assessing the future liver remnant function.