*2.3.2.1 Type A*

Segment I is the caudate lobe, which is supplied by three to six small portal vein branches derived directly from the left and right main portal veins. Segments II and III are supplied by fourth-level portal vein branches derived from the superior and inferior outer aspects of the umbilical part of the left main portal branch. Segment IV is supplied by the fourth-level branch of the left portal vein.

**Figure 1.**

*(a–d) The three-dimensional (3D) reconstruction results of the liver, hepatic vein, and portal vein using Hisense CAS and integration.*

*A New Liver Segmentation Based on Digital Liver Portal Vein Ramification Using… DOI: http://dx.doi.org/10.5772/intechopen.111542*

The left lobe nomenclature, including segments I to IV, is similar for all four types (**Figure 2**). The right portal vein divides into the right anterior and the right posterior branches. The right anterior branch further divides into two main branches, the cephalic and caudal branches, or the ventral and dorsal branches, depending on the angle of their branching. The caudal or ventral branch supplies segment V, whereas the cephalic or dorsal branch supplies segment VIII (**Figure 3a**).

Segment VI is the area supplied by the fourth-level portal vein derived from the outer inferior aspect of the right liver following the third-level branch of the right portal vein branch. Segment VII is the area supplied by fourth-level portal vein derived from the superior outer aspect of the right liver following the third-level branch of the right portal vein branch (**Figure 3b**).
