Analysis of the Hepatic Segments on the Isotropic Multi-planar Reformatted CT Images

Yim, Yoo Jeong; Lee, Won Jae; Jeon, Yong Hwan; Lee, Jongmee; Park, Kwang Bo; Lim, Hyo Keun; Lim, Jae Hoon

Abstract

PURPOSE: We wanted to evaluate the diverse distribution and relation of the hepatic segments, as divided by the portal venous territories, on the isotropic multi-planar reformatted (MPR) CT images and we wanted to find their correlation to the intrahepatic venous structures.
MATERIALS AND METHODS
Fifty adult patients who underwent portal phase CT images and who had the normal liver contours at CT were included in our study. The portal phase images were obtained with a slice collimation and reconstruction interval of 1.25 mm, and they were reformatted in the coronal and sagittal planes with a slab thickness of 3 mm. For analysis of these MPR images, various terms were newly defined according to the portal venous territories (e.g., three vertical planes [right, middle and left] and one transverse plane and their plane angles, the transverse and longitudinal angles). Also, the dominant segments of the right lobe were newly divided into the S7- and S8-dominant types by comparing the transverse angles. The imaging analysis was then conducted for the following: (1) the diversity of the three vertical planes and the one transverse plane and their plane angles, (2) the proportion of the dominant segments of the right lobe and their relation with the plane angles, and (3) the correlation between the dominant segments and the intrahepatic venous structures.
RESULTS
The number of the S7- and the S8-dominant types was 21 and 29, respectively. The vertical and transverse planes were undulating and diverse according to the dominant segments as follows: the plane angles of the right vertical and middle vertical planes were more vertical in the S7-dominant type than in the S8-dominant type (p < 0.001). The right transverse plane angle was more horizontal in the S8-dominant type (p < 0.05). The left transverse plane angle seemed to be rather vertical than horizontal. For the intrahepatic venous structures, despite of our limited data, the anomalous intrahepatic venous structures might have some correlation with the dominant segments.
CONCLUSION
According to our results, we suggest that the isotropic MPR images could successfully depict the vertical and transverse planes of the real hepatic segments, as divided by the portal venous territories, which were diverse according to their dominant types.