**4. Application of CAS in pediatric precise oncological surgery**

According to a survey by the International Society of Pediatric Oncology, the incidence of pediatric tumors has increased at a rate of 2.8% each year over the past 10 years, and pediatric malignant solid tumors have become a major cause of illness and death in children. Primary surgical resection or surgical resection after other treatments is still recognized as the current first choice for the treatment of pediatric malignant solid tumors and is the only means to achieve a radical cure for malignant tumors. However, the necessity of pursuing radical surgery in children and the special characteristics of pediatric tumors put forward higher requirements for pediatric precision surgery.

#### **4.1 Pediatric liver tumor**

The anatomical structure of the liver is complex, and internal vascular and biliary tract variants are common, especially in the hepatic vein. The structure of the intrahepatic vascular system in pediatric patients is very delicate, and the organ is small in size and poorly tolerant to surgical trauma. Moreover, pediatric liver tumors are often huge, complex, fast-growing, and highly malignant. Tumors often squeeze and deform the surrounding blood vessels, and the compression or invasion of the adjacent liver area is difficult to identify. Large tumors involving the hepatic porta and tumors originating from the hepatic porta are still difficult to treat surgically. In addition, pediatric liver volume changes greatly with age and weight, so individualized liver anatomy and volume analyses are very important [11].

Hepatoblastoma (HB) is the most common primary malignant tumor of the liver in children. Its incidence rate is the highest among infants and children under 5 years old, with an annual incidence of approximately 1.5 cases per 1 million. The increasing incidence year by year and disparities between races have attracted widespread attention. With the combination of surgery and chemotherapy, especially neoadjuvant chemotherapy, the prognosis of children with HB has improved significantly, with survival rates increasing from 30% to approximately 80% [12, 13]. However, surgical resection is still an important and indispensable treatment for HB, and whether the tumor can be completely removed with a sufficient liver remnant volume is the key factor affecting the prognosis of such children [14].

All current collaborative trial groups used PRETEXT/POSTTEXT to assess the surgical resectability of HB before surgery. This staging is based on 2D cross-sectional images and is performed on the basis of Couinaud's liver segmentation by determining the number of consecutive tumor-free liver sections. In practice, this approach is of limited help to the surgeon, and the assessment of staging and surgical resectability by window-level selection and artificial measurements is severely limited by anatomical basis, image interpretation experience, and surgical experience. Only a very rough estimate of the expected surgical procedure difficulty can be made. In addition, although Couinaud's segmentation is very classical and practical, it is limited by the small number of dissection cases available when the classification was established and some differences between the isolated and living liver. PRETEXT also provides a detailed and cumbersome description of vascular variants, but as definitions, their clinical application is limited [15].

From the point of view of surgical resection, regardless of the strategy and staging, what must be assessed is vascular involvement, which was also defined by PRETEXT as the annotation factors V and P [13]. In clinical practice, the extent of tumor involvement in major vessels is difficult to assess due to the limitations of 2D images and the deformation variability of the liver vascular system. Another key consideration for surgical resection is the future liver remnant (FLR). An adequate postoperative FLR volume is important, as a small FLR volume can lead to acute liver failure or even death. For HB, guidelines emphasize anatomic hepatic resection, which allows for more normal liver tissue located >1 cm outside the tumor to be removed. Non-anatomic hepatic resection for advanced HB is often considered, such as extended major hepatectomies, mid-liver lobectomy, or segmental resections, which require more precise assessments of FLR [16].

3D imaging technology based on CT images is able to display the positional relationships of the liver, tumor, and all internal ductal structures in a comprehensive and simultaneous manner to achieve accurate evaluations of distances in three-dimensional space, which has obvious advantages in vessels with compression deformation or individual anatomical variations. The ability to track the route of each vessel and determine the drainage segment of each vein is important for determining individualized liver segmental anatomy [15, 17]. In addition, this technology allows for continuous assessments of preoperative chemotherapy and postoperative liver regeneration, which is of greater value in selecting the optimal timing of surgical resection and assessing postoperative liver recovery. Hisense CAS was developed based on enhanced pediatric CT data, so it has more advantages in displaying pediatric liver tumors, especially huge tumors compressing the hepatic porta. Hisense CAS can clearly show the relationships between the tumor and blood vessels and improve the resectability of liver tumors.

Two typical cases of patients with HB who underwent surgical planning with Hisense CAS are shown below. **Figure 3** demonstrates a 4-year-old boy with a large

**Figure 3.** *Computer-assisted resection of the liver tumor with hepatic vein variation.*
