An Introduction to GPU Accelerated Surgical Simulation

A Systematic Review of Real-Time Medical Simulations with Soft-Tissue Deformation: Computational Approaches, Interaction Devices, System Architectures, and Clinical Validations

Simulating deformations of soft tissues is a complex engineering task, and it is even more difficult when facing the constraint between computation speed and system accuracy. However, literature lacks of a holistic review of all necessary aspects (computational approaches, interaction devices, system architectures, and clinical validations) for developing an effective system of soft-tissue simulations. This paper summarizes and analyses recent achievements of resolving these issues to estimate general trends and weakness for future developments. A systematic review process was conducted using the PRISMA protocol with three reliable scientific search engines (ScienceDirect, PubMed, and IEEE). Fifty-five relevant papers were finally selected and included into the review process, and a quality assessment procedure was also performed on them. The computational approaches were categorized into mesh, meshfree, and hybrid approaches. The interaction devices concerned about combination between virtual surgical instruments and force-feedback devices, 3D scanners, biomechanical sensors, human interface devices, 3D viewers, and 2D/3D optical cameras. System architectures were analysed based on the concepts of system execution schemes and system frameworks. In particular, system execution schemes included distribution-based, multithread-based, and multimodel-based executions. System frameworks are grouped into the input and output interaction frameworks, the graphic interaction frameworks, the modelling frameworks, and the hybrid frameworks. Clinical validation procedures are ordered as three levels: geometrical validation, model behavior validation, and user acceptability/safety validation. The present review paper provides useful information to characterize how real-time medical simulation systems with soft-tissue deformations have been developed. By clearly analysing advantages and drawbacks in each system development aspect, this review can be used as a reference guideline for developing systems of soft-tissue simulations.

A tensor-mass method-based vascular model and its performance evaluation for interventional surgery virtual reality simulator

BACKGROUND

Physics-based vascular modelling is an essential issue to be addressed in the development of the endovascular interventional surgery training system, which helps to shorten the training period of novice surgeons to obtain dexterous skills of surgical operation.

METHODS

A blood vessel model based on tensor-mass method (TMM) is formulated and implemented in this context. A multimodel representation is adopted for the vascular model, including the mechanical, visual, and collision model. Triangular and tetrahedral TMM are formulated and implemented in Simulation Open-source Framework Architecture (SOFA). An extensional formulation and analysis of two typical methods are implemented in SOFA. Meanwhile, a set of experiments were conducted to test the refresh rate, the stability, and the visual realism of the vascular deformation simulation, integrating with TMM, mass-spring model, and finite element method.

RESULTS

The experimental and subjects' testing results prove that TMM outperforms the current physically based methods in realistic and real-time vascular deformation simulation, which provides a refresh rate up to 256 frame per second on a triangular vascular topology.

CONCLUSIONS

The vascular model presented herein provides a fundamental module meeting the real-time and realistic requirements of our endovascular interventional surgery simulator.

Mathematical Modeling and Virtual Reality Simulation of Surgical Tool Interactions With Soft Tissue: A Review and Prospective

This is an informed assessment of the state of the art and an extensive inventory of modeling approaches and methods for soft tissue/medical cutting tool interaction and of the associated medical processes and phenomena. Modeling and simulation through numerical, theoretical, computational, experimental, and other methods was discussed in comprehensive review sections each of which is concluded with a plausible prospective discussion biased toward the development of so-called virtual reality (VR) simulator environments. The finalized prospective section reflects on the future demands in the area of soft tissue cutting modeling and simulation mostly from a conceptual angle with emphasis on VR development requirements including real-time VR simulator response, cost-effective “close-to-reality” VR implementations, and other demands. The review sections that serve as the basis for the suggested prospective needs are categorized based on: (1) Major VR simulator applications including virtual surgery education, training, operation planning, intraoperative simulation, image-guided surgery, etc. and VR simulator types, e.g., generic, patient-specific and surgery-specific and (2) Available numerical, theoretical, and computational methods in terms of robustness, time effectiveness, computational cost, error control, and accuracy of modeling of certain types of virtual surgical interventions and their experimental validation, geared toward ethically driven artificial “phantom” tissue-based approaches. Digital data processing methods used in modeling of various feedback modalities in VR environments are also discussed.

Towards immersive virtual reality (iVR): a route to surgical expertise

Surgery is characterized by complex tasks performed in stressful environments. To enhance patient safety and reduce errors, surgeons must be trained in environments that mimic the actual clinical setting. Rasmussen’s model of human behavior indicates that errors in surgical procedures may be skill-, rule-, or knowledge-based. While skill-based behavior and some rule-based behavior may be taught using box trainers and ex vivo or in vivo animal models, we posit that multimodal immersive virtual reality (iVR) that includes high-fidelity visual as well as other sensory feedback in a seamless fashion provides the only means of achieving true surgical expertise by addressing all three levels of human behavior. While the field of virtual reality is not new, realization of the goals of complete immersion is challenging and has been recognized as a Grand Challenge by the National Academy of Engineering. Recent technological advances in both interface and computational hardware have generated significant enthusiasm in this field. In this paper, we discuss convergence of some of these technologies and possible evolution of the field in the near term.

High-speed nonlinear finite element analysis for surgical simulation using graphics processing units

The use of biomechanical modelling, especially in conjunction with finite element analysis, has become common in many areas of medical image analysis and surgical simulation. Clinical employment of such techniques is hindered by conflicting requirements for high fidelity in the modelling approach, and fast solution speeds. We report the development of techniques for high-speed nonlinear finite element analysis for surgical simulation. We use a fully nonlinear total Lagrangian explicit finite element formulation which offers significant computational advantages for soft tissue simulation. However, the key contribution of the work is the presentation of a fast graphics processing unit (GPU) solution scheme for the finite element equations. To the best of our knowledge, this represents the first GPU implementation of a nonlinear finite element solver. We show that the present explicit finite element scheme is well suited to solution via highly parallel graphics hardware, and that even a midrange GPU allows significant solution speed gains (up to 16.8 x) compared with equivalent CPU implementations. For the models tested the scheme allows real-time solution of models with up to 16,000 tetrahedral elements. The use of GPUs for such purposes offers a cost-effective high-performance alternative to expensive multi-CPU machines, and may have important applications in medical image analysis and surgical simulation.

Surgical simulation – a new tool to evaluate surgical incisions in congenital heart disease?

We introduce a new concept for preoperative planning and surgical education in congenital heart disease: surgical simulation. Recent advances in three-dimensional image acquisition have provided a new means to virtually reconstruct accurate morphological models while computer visualisation hardware now allows simulation of elastic tissue deformations interactively. Incision simulation is performed in two patients with complex congenital heart disease to preoperatively evaluate potential corrective surgical strategies. The relevant cardiac morphology was correctly depicted by the virtual models on which arbitrary incisions could be performed. By visualising the morphology in respect to each incision, different surgical strategies could be evaluated pre-operatively. We have taken the first step towards a clinically useful incision simulator for procedures in congenital heart disease and made an initial evaluation. With further developments it is likely that new tools for patient-specific preoperative planning and surgical training will emerge based on the presented ideas.