Finite Element Model-Based Simulation of Liver Deformation for Vessel Tracking

In minimally invasive surgery, knowing the position of internal structures of tissue such as vessels and tumors is a challenge. Surgeons only depend on preoperative CT images to know positions of vessels and tumors, but liver is deformed by different surgical procedures. The preoperative information is no longer precise. With the help of vessel-tracking system, surgeons can operate the surgical tasks more intuitively and decrease the risk from cutting large vessels and tumors. In this thesis, finite element model built from preoperative CT is used to calculate deformations. The difference between intraoperative and preoperative surface data is used as displacement boundary conditions applied to simulate the deformations. After finite element computation, the intraoperative positions of vessels and tumors are obtained. The proposed algorithms are first validated through simulation data based on surgical scenario in minimally invasive surgery, then validated through ex vivo porcine liver experiment data. The mean error of liver surface is 0.35mm and mean error of internal structure is 0.28mm in simulation. The mean error of liver surface is 0.86mm and mean error of internal structures is 2.26mm in ex vivo porcine liver experiment.