*2.3.3 III Segmental volumes for types A, B, and C of Dong's liver segmentation system*

The volumes of each of the liver segments of the different types are presented in **Tables 3**–**6**. For type A, segments V and VIII account for 15.78% (±5.12) and 16.43% (±5.18) of the total liver volume, respectively. For type B, the volumes of segments V, VIII, and IX account for 10.36% (±3.72), 11.84% (±3.28), and 12.69% (±3.70), respectively. The volume of the right-posterior (RP) segment of type C was smaller than that of segments VI and VII of type A and type B (26.379% [±5.613] and 24.447 [±5.025], p < 0.01).

#### **Figure 6.**

*(a) The right anterior portal vein is derived from the left portal vein main trunk. (b) The P6 portal vein is derived from the right anterior portal vein. (c) The portal vein trunk has trifurcation at the porta hepatis and divides into the left, right anterior, and right posterior branches. (d) The right anterior portal vein is derived from the saccule of the left branch. (e) The right anterior lobe has a dominant supply from seven branches that are simultaneously derived from the right anterior portal vein. (f) The P2 and P3 branches of the left portal vein share a common trunk.*


#### **Table 1.**

*Distribution of liver segmentation in different sexes.*

Accurate preoperative knowledge of the liver anatomy and volume is essential for performing safe liver resections [1, 10, 14, 15]. We proposed a liver segmentation system to enable better classification of the different types for individual patients to assist with their preoperative surgical planning. Segmental liver volume, which is useful for the preoperative evaluation of remnant liver volume, was also predicted.

Recently, many studies have proposed different methods of liver segmentation based on variations in the vascular anatomy of the liver [11–13]. Functional liver segmentation that included eight segments based on portal vein blood supply and hepatic venous drainage was most well-known and applied in clinical work [4]. However, the actual anatomical segmentation of the liver varied substantially in some cases.

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


#### **Table 2.**

*Distribution of liver segmentation in pediatric and adult groups.*


#### **Table 3.**

*Volume ratio for each type A segment of Dong's liver segmentation (%).*


#### **Table 4.**

*Volume ratio for each type B segment of Dong's liver segmentation (%).*


#### **Table 5.**

*Volume ratio for each type C-a segment of Dong's liver segmentation (%).*


#### **Table 6.**

*Volume ratio for each type C-b segment of Dong's liver segmentation (%).*

Based on artificial intelligence, the development of imaging technology has enabled 3D reconstruction of the digital liver model in a CT DICOM file by using simulation software [16, 17]. The possibility of observing the anatomical relationship of the portal vein and hepatic vein in the liver from different angles allows for individualized evaluation of liver segmentation and subsequent surgical planning [18–23]. Based on pediatric patients' CT DICOM data, we developed software called Hisense CAS [17, 24, 25], which could accurately reconstruct the intrahepatic portal vein branches up to their fourth level. In the present study, we analyzed 759 digital livers; based on the variation of the fourth-level portal vein branch, we proposed Dong's liver segmentation system. This system attempts to include all types of anatomical variations in the liver.

We found that the portal vein branches in the left hepatic lobe, which was divided into segments II, III, and IV, were relatively consistent. However, there were several variations in the right liver that cannot be described by a single segmentation method. Consequently, we classified them into four types: A, B, C, and D. For types A and B, segments VI and VII are supplied by a fourth-level portal vein derived from the outer, inferior, and superior aspects of the right posterior portal vein branches.

Couinaud divided cephalic segment VIII and caudal segment V based on the right anterior portal vein. This was disputed by a recent study that proposed that the right anterior divides into ventral and dorsal branches [11, 13]. Our study findings demonstrated that in some livers, the right anterior usually divides into two main branches, either cephalic and caudal or ventral and dorsal. We classified this as type A. Our observations suggest that a preoperative understanding of the angle of the portal vein branch is necessary for the right-anterior branch to avoid intraoperative injuries. Furthermore, the right anterior portal vein branch may also divide into three main branches, including the caudal (P5), cephalic-dorsal (P8), and cephalic-ventral (P9) branches. We classified this as type B.

The right posterior portal vein branch of type C is a single main branch with several small sector-shaped branches that supply the right-posterior lobe. These anatomical variations are important for segmental, subsegmental, and combinedsegmental precision resections of the right liver.

A variety of special variations that could not be categorized into the first three types were included as type D. This strategy of grouping the special variants into one type may facilitate a full understanding of the complexity of liver anatomy. A higher proportion of such variance also supported the need for individualized precision surgery. To perform precision hepatectomy, liver segmentation should be performed based on individual liver models established using each patient's imaging data preoperatively so that virtual surgery and remnant liver volume may be evaluated by using the 3D simulation software.

According to Kumon's criteria, the caudate lobe (segment I) comprises three parts: the Spiegel lobe, the paracaval portion, and the caudate carina. Because of the uniqueness of the caudate lobe blood supply, the Spiegel lobe is supplied by one or two caudate lobe portal branches. Variations in the portal blood supply to the caudate lobe are very common. In our study, a considerable proportion of subjects were found to have two to five branches that were derived from the left and right portal veins supplying the caudate lobe. However, the actual number of such branches could not be accurately determined because of their tiny size and inadequate CT resolution. Because of these tiny vessels, we suggest that surgeons should demonstrate extra care during caudate lobe surgery.

We did not find any significant differences in sex and age using Dong's liver segmentation. Because our data were from the Chinese population, the differences in the liver anatomy of people from various races and regions need further exploration.

The average volume of each segment of the different segmentation types can be used for predicting remnant liver volume to ensure safe anatomic hepatectomy. *A New Liver Segmentation Based on Digital Liver Portal Vein Ramification Using… DOI: http://dx.doi.org/10.5772/intechopen.111542*

However, because of the large diversity in portal vein anatomy, it is our opinion that individualized volume measurements are critical for the safety of anatomic hepatectomy, especially in patients with large tumors, impaired liver function, or atypical portal vein branching.

Artificial intelligence technology has made significant breakthroughs and clinical applications in the field of precision surgery. The development of digital medicine has provided new perspectives regarding liver segmentation. We believe that Dong's liver segmentation system and segmental liver volume will enable a better understanding of liver anatomy and will be useful for liver surgeons.
