99mTc-galactosyl human serum albumin (99mTc-GSA) single-photon emission CT (SPECT) was developed to facilitate investigations of regional hepatic function. A disadvantage of conventional 99mTc-GSA SPECT was poor anatomical resolution, and this newly developed SPECT has a tremendously improved anatomical resolution owing to the fusion of CT and 99mTc-GSA SPECT. Recent reports have indicated that accurate regional function, based on precise anatomical information, could be evaluated using this technique.