Example of Laparoscopic Surgery Simulation System
This subsection shows examples of laparoscopic simulation systems mainly based on patient-specific organ models generated by CA. In this section, we show an example of laparoscopic gastrectomy.
Organ Segmentation and Labeling
Organ regions are extracted from preoperative CT volume datasets. To enable the algorithm to distinguish between artery and vein regions on CT images, arterial-
Fig. 4.12 Abdominal organ segmentation for laparoscopic surgery simulation
and venous-phase data are utilized. For a gastrectomy, the following organs are segmented: (a) artery, (b) vein, (c) liver, (d) spleen, (e) kidneys, and (f) pancreas (Fig. 4.12). Segmentation is performed in automated or semiautomated way and utilized for image generation (Fig. 4.13).
In laparoscopic surgery, the abdominal cavity is expanded by inflation with CO2 gas. In arthroscopic surgery simulation, such demotion should be simulated to generate a more realistic simulation image. The abdominal wall region is extracted from CT data and is separated from the rest of the body. Elastic modes based on a spring- mass model are generated to simulate large deformations of the abdominal wall. By combining n x n x n voxels into one deformation element, we allocate springs, dampers, and masses.
Inflation force is added to all nodes located at the boundary of the abdominal wall and the rest of the body. The deformation elements are deformed until deformation converges. Deformation parameters are determined based on the physical properties of a real human body. After the convergence of deformation, we deform an original CT volume to obtain a CT volume with a pneumoperitoneum. This process
Fig. 4.13 Simulation image generation based on segmentation results
Fig. 4.14 Example of virtual pneumoperitoneum
generates a deformed CT volume reflecting virtual pneumoperitoneum (Fig. 4.14). By rendering deformed volume with multi-organ segmentation results, it is possible to generate a virtual laparoscopic view (Fig. 4.15).
Fig. 4.15 Example of laparoscopic surgery simulation
Fig. 4.16 Example of anatomical name display on simulation image
Anatomical Name Display
Anatomical labeling information gives more information for simulation. Anatomical name overlay is also performed in generating a simulation image (Fig. 4.16).
K. Mori et al.