Automatic estimation of a resected liver region using a tumor domination ratio - Emerging Trends in Image Processing, Computer Vision, and Pattern Recognition - page 305

vein, and HCC metastasizes in the downstream direction through the portal vein. Therefore,
the cancer-related regions can be estimated based on the perfused region.
FIGURE 1 Vascular system of the liver.
FIGURE 2 HCC (cancer) metastasizing model.
Overestimating the perfused region tends to prevent metastasizing and reduce recurrence
of HCC since a large region including the tumor is resected. However, it increases the possib-
ility of the postoperative liver failure. Therefore, the volume of the perfused region should be
minimized while including all the perfused regions of the portal vein feeding the tumor.
Some practical software programs for 3D simulation and preoperative planning have been
developed like Hepavision (MeVis Medical Solutions AG, Bremen, Germany) [ 4 ] , OVA (Hita-
chi, Tokyo, Japan) [ 5 ] , and Synapse VINCENT (Fujifilm Medical, Tokyo, Japan) [ 6 ] . In preop-
erative planning, surgeons search for the combination of the cut-points on the portal vein in a
trial-and-error way until the tumor is covered by the perfused regions of the portal-vein cut-
points. However, it is difficult and time-consuming for surgeons to find optimal or near-op-
timal combination since the portals vein has complex structure, that is, it has many branches.
As a result, surgeons tend to select simple combinations, and this leads to overestimation of
the perfused region.
To solve this problem, the method to compute the optimal perfused regions has been deve-
loped, where the volume is minimized while including all the perfused region of the tumor-
related portal vein [ 7 ]. In order to find the tumor-related part of the portal vein accurately,
the tumor domination ratio (TDR) is defined which reflects how much volume of the tumor a
portal-vein point feeds. The TDR allows to pick up all the tumor-related points of the portal
vein, and the total of the regions perfused by them is determined to be the resected region.
This chapter extends the work [ 7 ] by adding explanations, evaluations, and a method consid-
ering a more practical condition.
The rest of this chapter is organized as follows. In Section 2 , the basic method to find the
ideal resected region is explained where practical conditions used in the real surgeries are
not considered. In Section 3 , its extension is explained where practical conditions such as the
branch points and the radiuses of the vessels are considered. Section 4 describes more practic-
all estimation considering hepatic veins as well as portal veins. Section 5 is conclusion.