PurposeOur aim was to determine the utility of Tc-99m-diethylenetriaminepentaacetic acid-galactosyl human serum albumin single-photon-emission computed tomography (99mTc-GSA SPECT/CT) fusion imaging for detecting incomplete portal vein embolization (PVE).Materials and methodsFifty-five candidates underwent PVE. Among them, five underwent second PVE. Detectability of first inadequate PVE using CT and 99mTc-GSA SPECT/CT fusion imaging was analyzed.ResultsCases of inadequate PVE were detected in three patients using CT and in five using 99mTc-GSA SPECT/CT fusion imaging. Fusion imaging detected two cases of insufficient PVE in which portal branches were apparently well embolized on CT. Median value for volumetric rate in the embolized liver was 63.3% after the first PVE and 54.7% after the second (P < 0.01). Median functional rate value in embolized liver was 60.1% after the first PVE and 49.4% after the second (P < 0.01). Median value for change of volumetric and functional rates in embolized liver after the second PVE was 7.1 and 10.3%, respectively, and change of functional rate was greater than that of volumetric rate (P < 0.01).Conclusions99mTc-GSA SPECT/CT fusion imaging was useful for detecting inadequate PVE, and second PVE was effective for increasing volumetric and functional rates.