ObjectivesThe aim of the study was to accurately examine the functional volume (RI-vol) of the hepatic segments on single photon emission computed tomography/computed tomography (CT) fusion imaging by technetium-99m galactosyl human serum albumin scintigraphy and compare it with the RI-vol and morphological volume obtained on computed tomography (CT-vol). MethodsIn 60 patients with various liver background statuses who had undergone hepatectomy, the RI-vol and CT-vol were examined in each sector using imaging analysis. The values from a control group (n=91) were used as reference data. ResultsThe mean RI-vol and CT-vol of the right liver were 64±10 and 63±6%, respectively, whereas the values for the left liver were 36±10 and 37±6%, respectively. Compared with the control group, the ratios in each hemiliver were similar. The mean RI-vol and CT-vol for each sector were also similar, and significant positive correlations were identified between the two volumes (P<0.01). In four patients with hepatic tumors involving the main hepatic vessels or the bile duct and in 10 patients who had undergone portal vein embolization, the actual RI-vol in the injured sector was significantly decreased compared with CT-vol (P<0.05). There were marked changes in functional volume in segment 6+7 and segment 2+3 after portal vein embolization (P<0.05). ConclusionVolumetric measurement using single photon emission computed tomography/CT imaging with technetium-99m galactosyl human serum albumin scintigraphy is useful for evaluating the functional volume in separated livers and offers a good reflection of the background liver status.