Frank Tendick

A survey of surgical simulation: applications, technology, and education

Surgical simulation for medical education is increasingly perceived as a valuable addition to traditional teaching methods. Simulators provide a structured learning experience, permitting practice without danger to patients, and simulators facilitate the teaching of rare or unusual cases. Simulators can also be used to provide an objective assessment of skills. This paper is a survey of current surgical simulator systems. The components of a simulator are described, current research directions are discussed, and key research questions are identified.

Adaptive Nonlinear Finite Elements for Deformable Body Simulation Using Dynamic Progressive Meshes

Realistic behavior of deformable objects is essential for many applications such as simulation for surgical training. Existing techniques of deformable modeling for real time simulation have either used approximate methods that are not physically accurate or linear methods that do not produce reasonable global behavior. Nonlinear finite element methods (FEM) are globally accurate, but conventional FEM is not real time. In this paper, we apply nonlinear FEM using mass lumping to produce a diagonal mass matrix that allows real time computation. Adaptive meshing is necessary to provide sufficient detail where required while minimizing unnecessary computation. We propose a scheme for mesh adaptation based on an extension of the progressive mesh concept, which we call dynamic progressive meshes.

A critical study of the mechanical and electrical properties of the PHANToM haptic interface and improvements for high-performance control

This paper presents a critical study of the mechanical and electrical properties of the PHANToM haptic interface and improvements to overcome its limitations for applications requiring high-performance control. Target applications share the common requirements of low-noise/granularity/latency measurements, an accurate system model, high bandwidth, the need for an open architecture, and the ability to operate for long periods without interruption while exerting significant forces. To satisfy these requirements, the kinematics, dynamics, high-frequency dynamic response, and velocity estimation of the PHANToM system are studied. Furthermore, this paper presents the details of how the unknown subsystems of the stock PHANToM can be replaced with known, high-performance systems and how additional measurement electronics can be interfaced to compensate for some of the PHANToMs shortcomings. With these modifications, it is possible to increase the maximum achievable virtual wall stiffness by 35, active viscous damping by 120, and teleoperation loop gain by 50 over the original system. With the modified system, it is also possible to maintain higher forces for longer periods without causing motor overheating.

A Virtual Environment Testbed for Training Laparoscopic Surgical Skills

With the introduction of minimally invasive techniques, surgeons must learn skills and procedures that are radically different from traditional open surgery. Traditional methods of surgical training that were adequate when techniques and instrumentation changed relatively slowly may not be as efficient or effective in training substantially new procedures. Virtual environments are a promising new medium for training. This paper describes a testbed developed at the San Francisco, Berkeley, and Santa Barbara campuses of the University of California for research in understanding, assessing, and training surgical skills. The testbed includes virtual environments for training perceptual motor skills, spatial skills, and critical steps of surgical procedures. Novel technical elements of the testbed include a four-DOF haptic interface, a fast collision detection algorithm for detecting contact between rigid and deformable objects, and parallel processing of physical modeling and rendering. The major technical challenge in surgical simulation to be investigated using the testbed is the development of accurate, real-time methods for modeling deformable tissue behavior. Several simulations have been implemented in the testbed, including environments for assessing performance of basic perceptual motor skills, training the use of an angled laparoscope, and teaching critical steps of the cholecystectomy, a common laparoscopic procedure. The major challenges of extending and integrating these tools for training are discussed.

Design of bilateral teleoperation controllers for haptic exploration and telemanipulation of soft environments

In this letter, teleoperation controller design for haptic exploration and telemanipulation of soft environments is studied. First, a new measure for fidelity in teleoperation is introduced which quantifies the teleoperation systems ability to transmit changes in the compliance of the environment. This sensitivity function is appropriate for the application of telesurgery, where the ability to distinguish small changes in tissue compliance is essential for tasks such as detection of embedded vessels. The bilateral teleoperation controller design problem is then formulated in a task-based optimization framework as the optimization of this metric, with constraints on free-space tracking and robust stability of the system under environment and human operator uncertainties. The control design procedure is illustrated with a case study. The analysis is also used to evaluate the effectiveness of using a force sensor in a teleoperation system.

A laparoscopic telesurgical workstation

In this paper, various aspects of robotic telesurgery are studied. After a general introduction to laparoscopic surgery and medical applications of robotics, the UC Berkeley/Endorobotics Inc./UC San Francisco Telesurgical Workstation, a master-slave telerobotic system for laparoscopic surgery, is introduced, followed by its kinematic analysis, control, and experimental results. Some conceptual and future issues on telesurgery are discussed, including teleoperation and hybrid control, focusing on the special requirements of telesurgery.

Robotics for telesurgery: second generation Berkeley/UCSF laparoscopic telesurgical workstation and looking towards the future applications

Robotic telesurgery is a promising application of robotics to medicine, aiming to enhance the dexterity and sensation of regular and minimally invasive surgery through using millimeter‐scale robotic manipulators under the control of the surgeon. In this paper, the telesurgical system will be introduced with discussion of kinematic and control issues and presentation of in vitro experimental evaluation results.

Human-machine interfaces for minimally invasive surgery

Increasing numbers of surgical procedures are performed using minimally invasive techniques, in which trauma to external tissue is minimized. Unfortunately, reduced access reduces dexterity, limits perception, increases strain and the likelihood of error, and lengthens procedure time. Surgical technology must improve the interface between task requirements and human abilities. This paper describes three projects to evaluate and improve the human interface in laparoscopic surgery, or minimally invasive surgery of the abdomen: (a) measurement of movement trajectories under different visual conditions to determine the effect of viewing geometry, (b) the development of virtual environments for training, and (c) the development of haptic interfaces and control algorithms for teleoperative surgery.

Multirate simulation for high fidelity haptic interaction with deformable objects in virtual environments

Haptic interaction is an increasingly common form of interaction in virtual environment simulations. This medium introduces some new challenges. In this paper we study the problem arising from the difference between the sampling rate requirements of haptic interfaces and the significantly lower update rates of the physical models being manipulated. We propose a multirate simulation approach which uses a local linear approximation. The treatment includes a detailed analysis and experimental verification of the approach. The proposed method is also shown to improve the stability of the haptic interaction.

A comparison of position and rate control for telemanipulations with consideration of manipulator system dynamics

Position and rate control are the two common manual control modes in teleoperations. Human operator performance using the two modes is evaluated and compared. Simulated three-axis pick-and-place operations are used as the primary task for evaluation. First, ideal position and rate control are compared by considering several factors, such as joystick gain, joystick type, display mode, task, and manipulator work space size. Then the effects of the manipulator system dynamics are investigated by varying the natural frequency and speed limit. Experimental results show that ideal position control is superior to ideal rate control, regardless of joystick type or display mode, when the manipulation work space is small or comparable to the human operators control space. Results also show that when the manipulator system is slow, the superiority of position control disappears. Position control is recommended for small-work-space telemanipulation tasks, while rate control is recommended for slow wide-work-space telemanipulation tasks.