Constraint-Based Soft Tissue Simulation for Virtual Surgical Training

Abstract

Abstract-Most of surgical simulators employ a linear elastic model to simulate soft tissue material properties due to its computational efficiency and the simplicity. However, soft tissues often have elaborate nonlinear material characteristics. Most prominently soft tissues are soft and compliant to small strains, but after initial deformations they are very resistant to further deformations even under large forces. Such material characteristic is referred as the nonlinear material incompliant which is computationally expensive and numerically difficult to simulate. This paper presents a constraint-based finite element algorithm to simulate the nonlinear incompliant tissue materials efficiently for interactive simulation applications such as virtual surgery. Firstly, the proposed algorithm models the material stiffness behaviour of soft tissues with a set of three-dimensional strain limit constraints on deformation strain tensors. By enforcing a large number of geometric constraints to achieve the material stiffness, the algorithm reduces the task of solving stiff equations of motion with a general numerical solver to iteratively resolving a set of constraints with a nonlinear Gauss-Seidel iterative process. Secondly, as a Gauss-Seidel method processing constraints individually, in order to speed up the global convergence of the large constrained system a multi-resolution hierarchy structure is also used to accelerate the computation significantly, making interactive simulations possible at a high level of details. Finally, this paper also presents a simple-to-build data acquisition system to validate simulation results with ex vivo tissue measurements. An interactive virtual reality-based simulation system is also demonstrated.

Recent Developments and Future Challenges in Medical Mixed Reality

“…If a stereoscopic display is being used then there are techniques developed to generate more robust and precise tracking, such as the real-time visual odometry system using dense quadrifocal tracking [116]. In general, however, the accurate tracking of tissue surfaces in real time and realistic modelling of soft tissue deformation [117] remains an active research area.…”

Simulation‐Guided Tracheotomy in a Patient With Fibrodysplasia Ossificans Progressiva

“…These are more expensive, and linear elastic models tend to be used because they are simple and efficient to create. An algorithm to create a more suitable 3D model material has been described . These considerations may be included in planning for future 3D modeled in situ simulation surgical rehearsals.…”

“…An algorithm to create a more suitable 3D model material has been described. 10 These considerations may be included in planning for future 3D modeled in situ simulation surgical rehearsals. The other criticism of the simulation from the surveys was not having responsive hemodynamics that corresponded to the simulated airway emergencies.…”

The role of simulation in neurosurgery

“…A team of engineers and neurosurgeons from the University of Tübingen, Germany, developed a virtual neuroendoscopy system for surgical planning known as VIVENDI [73,74]. The developers stated that VIVENDI is a helpful tool assisting neurosurgeons in operative planning and intraoperative orientation [73,75].…”

“…The VR platform is a simulator for endoscopic transsphenoidal surgery that integrates haptic feedback via tactile tool manipulators [76]. The inventors state that the system enables the trainees to practice minimally invasive techniques in both anatomical and pathological scenarios [74].…”