Showing papers by "Septimiu E. Salcudean published in 2005"

Needle steering and motion planning in soft tissues

Abstract: In this work, needle insertion into deformable tissue is formulated as a trajectory planning and control problem. A new concept of needle steering has been developed and a needle manipulation Jacobian defined using numerical needle insertion models that include needle deflection and soft tissue deformation. This concept is used in conjunction with a potential-field-based path planning technique to demonstrate needle tip placement and obstacle avoidance. Results from open loop insertion experiments are provided.

Interactive simulation of needle insertion models

Abstract: A novel interactive virtual needle insertion simulation is presented. The simulation models are based on measured planar tissue deformations and needle insertion forces. Since the force-displacement relationship is only of interest along the needle shaft, a condensation technique is shown to reduce the computational complexity of linear simulation models significantly. As the needle penetrates or is withdrawn from the tissue model, the boundary conditions that determine the tissue and needle motion change. Boundary condition and local material coordinate changes are facilitated by fast low-rank matrix updates. A large-strain elastic needle model is coupled to the tissue models to account for needle deflection and bending during simulated insertion. A haptic environment, based on these novel interactive simulation techniques, allows users to manipulate a three-degree-of-freedom virtual needle as it penetrates virtual tissue models, while experiencing steering torques and lateral needle forces through a planar haptic interface.

Hand-held steerable needle device

Abstract: Minimally invasive percutaneous medical procedures are widely accepted in current clinical practice. However, with current techniques, the procedures are challenging and a high level of expertise is required to perform them successfully. This paper presents a novel steerable needle device for percutaneous interventions that allows the physician to steer the tip of the needle during insertion which eases the challenge associated with reaching the target. The steering concept uses slightly modified, off-the-shelf medical biopsy needles. A controlled lateral steering motion of over 30 mm during a 100-mm needle insertion is demonstrated with a 20-gauge needle in tissue-mimicking phantoms. A hand-held, motorized device has been built that actuates the needle base to produce a desired steering direction and magnitude at the tip. Steering commands may be supplied either by user input or by computer control. For the latter case, a method of software path planning has been developed that automatically steers the needle to a target.

Haptic rendering of rigid contacts using impulsive and penalty forces

Abstract: A new simulation approach is proposed to improve the stability and the perceived rigidity of contacts during haptic interaction with multirigid body virtual environments. The approach computes impulsive forces upon contact and penalty and friction forces during contact. The impulsive forces are derived using a new multiple collision resolution method that never increases the kinetic energy of the system. When new contacts arise, the impulsive forces generate large hand accelerations without requiring increased contact stiffness and damping. Virtual objects and linkages are regarded as points in the configuration space, and no distinction is made between them in the proposed approach.

3D needle-tissue interaction simulation for prostate brachytherapy

Abstract: This paper presents a needle-tissue interaction model that is a 3D extension of a prior work based on the finite element method. The model is also adapted to accommodate arbitrary meshes so that the anatomy can effectively be meshed using third-party algorithms. Using this model a prostate brachytherapy simulator is designed to help medical residents acquire needle steering skills. This simulation uses a prostate mesh generated from clinical data segmented as contours on parallel slices. Node repositioning and addition, which are methods for achieving needle-tissue coupling, are discussed. In order to achieve real-time haptic rates, computational approaches to these methods are compared. Specifically, the benefit of using the Woodbury formula (matrix inversion lemma) is studied. Our simulation of needle insertion into a prostate is shown to run faster than 1 kHz.

Local Model of Interaction for Haptic Manipulation of Rigid Virtual Worlds

Abstract: In this paper we propose a local model of rigid body interaction that provides users with convincing kinesthetic feedback while they manipulate a virtual tool within a rigid multibody virtual world. The virtual tool can be a rigid object or a linkage. The local model can interface a haptic device to any virtual environment simulation that provides the contact position, the contact normal direction, and the penetration depth of the virtual tool into the virtual world at the virtual tool contacts. The local model includes a proxy of the virtual tool that embeds an approximation of its geometry and of its dynamics, and that eliminates force discontinuities at model updates via proxy deformation. In addition, the model includes active and predicted virtual tool contacts. Predicted contacts are used to maintain force continuity and to better constrain users to tight virtual spaces. Experiments performed within a planar virtual world demonstrate that, compared to prior local models of rigid body interaction, the proposed model enables users to feel stiffer contacts and improves users' perception of free space in locally cluttered virtual environments.

Haptic Simulation of Linear Elastic Media with Fluid Inclusions

Abstract: We present a fast technique for simulating fluid-filled elastic objects with the Finite Element Method. By simulating the presence of fluid with hydrostatic fluid pressure, a quasi-static simulation of fluid can be achieved by applying a force boundary condition to the nodes on the fluidelastic interface. Using a proportional feedback control algorithm, a relationship between the volume and pressure of the fluid structure can be maintained. Optimal parameters for the control algorithm are found by determining the response of the elastic system to changes in pressure. This approach has been shown to agree with experimental deformation data taken from a fluid-filled gelatin phantom. Combining linear FEM methods with matrix condensation techniques and the tuned proportional feedback control allows for the simulation of a fluid-filled elastic object at real-time haptic update rates.

Haptic Rendering of Topological Constraints to Users Manipulating Serial Virtual Linkages

Abstract: This paper presents an approach for haptic rendering of topological constraints to users operating serial virtual linkages. In the proposed approach, a haptic device controller is designed to penalize users’ departure from the configuration manifold of the virtual linkage. This manifold is locally approximated through the range space of the Jacobian of the virtual linkage computed at the user’s hand. Simulations and controlled experiments performed using a planar haptic interaction system demonstrate that the proposed approach successfully constrains the users’ motion as required by the topology of the virtual linkage that they manipulate.