Computed tomography-based evaluation of segmental variation of liver density and its implications

Non-alcoholic fatty liver disease (NAFLD) has become a major health concern. Focal fat deposition frequently seems to involve segment IV b. This indicates a consistent pattern of fat deposition in the liver. The present study evaluates the pattern of fat distribution in the liver using computed tomogram (CT) attenuation index.

Two radiologists evaluated 517 non-contrast CT scan images of the abdomen and pelvis. Two 40-mm² regions of interest (ROIs) were selected from each segment. The hepatic segmental densities (HSDs) were obtained by calculating the mean densities of areas of corresponding liver segments. The mean hepatic attenuation (MHA) was quantified by obtaining the mean segmental densities. Densities were compared between the segments and with the MHA.

The mean age (SD) of the patients was 55.5 year (15.6), and 276 (53.4%) were males. The overall mean hepatic density was 53.05 (95% CI, 52.95-53.15) Hounsfield units (HU). The lowest mean HSD was observed in segment IV b and the highest mean HSD was observed in segment V. Segments I, IV a and IV b showed significantly lower mean HSDs and segments V, VI and VIII showed significantly higher mean HSDs compared with the overall mean MHA/mean hepatic density (MHD), whereas mean HSDs of segments II, III and VII were not significantly different from the overall mean MHA/MHD.

Segment IV b seems to be the most vulnerable site for fat deposition; focal lesions here should be carefully evaluated. Segments II, III and VII seem to closely represent MHD.