A Mechanics-Based Model for 3-D Steering of Programmable Bevel-Tip Needles (original) (raw)
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A model to predict deflection of bevel-tipped active needle advancing in soft tissue
2014
Active needles are recently being developed to improve steerability and placement accuracy for various medical applications. These active needles can bend during insertion by actuators attached to their bodies. The bending of active needles enables them to be steered away from the critical organs on the way to target and accurately reach target locations previously unachievable with conventional rigid needles. These active needles combined with an asymmetric bevel-tip can further improve their steerability. To optimize the design and to develop accurate path planning and control algorithms, there is a need to develop a tissue-needle interaction model. This work presents an energy-based model that predicts needle deflection of active bevel-tipped needles when inserted into the tissue. This current model was based on an existing energy-based model for bevel-tipped needles, to which work of actuation was included in calculating the system energy. The developed model was validated with needle insertion experiments with a phantom material. The model predicts needle deflection reasonably for higher diameter needles (11.6% error), whereas largest error was observed for the smallest needle diameter (24.7% error).
Experimental validation of curvature tracking with a programmable bevel-tip steerable needle
2018 International Symposium on Medical Robotics (ISMR), 2018
Needle steering systems are a topic of increasing research interest due to the many potential advantages associated with the ability to reach deep-seated targets while avoiding obstacles. Existing embodiments, such as those designed around a fixed bevel tip, are necessarily disruptive to the substrate, with the potential to cause a target to move away from the insertion trajectory, as well as potentially increasing the extent of tissue trauma at the needle interface, when compared to straight needles. To alleviate these issues, we proposed a biologically inspired design, which can steer without the need for duty-cycle spinning along the insertion axis or any active mechanisms at the tip. In this work, we demonstrate for the first time that our needle is able to steer within a deformable substrate, along with a user-defined trajectory in three-dimensional space. A simplified kinematic model is reported, which is subsequently used to design an adaptive strategy enabling the tracking of arbitrary curvatures along any given reference plane. Experimental results in gelatin are used to validate our model, as well as the performance of the controller under laboratory conditions.
Cyclic Motion Control for Programmable Bevel-Tip Needles to Reduce Tissue Deformation
Journal of Medical Robotics Research, 2018
Robotic-assisted steered needles aim to accurately control the deflection of the flexible needle’s tip to achieve accurate path following. In doing so, they can decrease trauma to the patient, by avoiding sensitive regions while increasing placement accuracy. This class of needle presents more complicated kinematics compared to straight needles, which can be exploited to produce specific motion profiles via careful controller design and tuning. Motion profiles can be optimized to minimize certain conditions such as maximum tissue deformation and target migration, which was the goal of the formalized cyclic, low-level controller for a Programmable Bevel-tip Needle (PBN) presented in this work. PBNs are composed of a number of interlocked segments that are able to slide with respect to one another. Producing a controlled, desired offset of the tip geometry leads to the corresponding desired curvature of the PBN, and hence desired path trajectory of the system. Here, we propose a cycli...
Needle-tissue interaction forces for bevel-tip steerable needles
2008 2nd IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics, 2008
The asymmetry of a bevel-tip needle results in the needle naturally bending when it is inserted into soft tissue. As a first step toward modeling the mechanics of deflection of the needle, we determine the forces at the bevel tip. In order to find the forces acting at the needle tip, we measure rupture toughness and nonlinear material elasticity parameters of several soft tissue simulant gels and chicken tissue. We incorporate these physical parameters into a finite element model that includes both contact and cohesive zone models to simulate tissue cleavage. We investigate the sensitivity of the tip forces to tissue rupture toughness, linear and nonlinear tissue elasticity, and needle tip bevel angle. The model shows that the tip forces are sensitive to the rupture toughness. The results from these studies contribute to a mechanics-based model of beveltip needle steering, extending previous work on kinematic models.
Mechanics of Flexible Needles Robotically Steered through Soft Tissue
The International Journal of Robotics Research, 2010
The tip asymmetry of a bevel-tip needle results in the needle naturally bending when it is inserted into soft tissue. This enables robotic needle steering, which can be used in medical procedures to reach subsurface targets inaccessible by straight-line trajectories. However, accurate path planning and control of needle steering requires models of needle-tissue interaction. Previous kinematic models required empirical observations of each needle and tissue combination in order to fit model parameters. This study describes a mechanics-based model of robotic needle steering, which can be used to predict needle behavior and optimize system design based on fundamental mechanical and geometrical properties of the needle and tissue. We first present an analytical model for the loads developed at the tip, based on the geometry of the bevel edge and material properties of softtissue simulants (gels). We then present a mechanics-based model that calculates the deflection of a bevel-tipped needle inserted through a soft elastic medium. The model design is guided by microscopic observations of needle-gel interactions. The energy-based formulation incorporates tissue-specific parameters, and the geometry and material properties of the needle. Simulation results follow similar trends (deflection and radius of curvature) to those observed in experimental studies of robotic needle insertion.
A Comparison of Needle Bending Models
Lecture Notes in Computer Science, 2006
Modeling the deflection of flexible needles is an essential part of needle insertion simulation and path planning. In this paper, three models are compared in terms of accuracy in simulating the bending of a prostate brachytherapy needle. The first two utilize the finite element method, one using geometric non-linearity and triangular plane elements, the other using non-linear beam elements. The third model uses angular springs to model cantilever deflection. The simulations are compared with the experimental bent needle configurations. The models are assessed in terms of geometric conformity using independently identified and pre-identified model parameters. The results show that the angular spring model, which is also the simplest, simulates the needle more accurately than the others.
Modeling and simulation of flexible needles
Medical Engineering & Physics, 2009
Needle insertion is performed in many clinical and therapeutic procedures. Tissue displacement and needle bending which result from needle-tissue interaction make accurate targeting difficult. For performing physicians to gain essential needle targeting skills, needle insertion simulators can be used for training. An accurate needle bending model is essential for such simulators. These bending models are also needed for needle path planning.
Estimation of model parameters for steerable needles
2010 IEEE International Conference on Robotics and Automation, 2010
Flexible needles with bevel tips are being developed as useful tools for minimally invasive surgery and percutaneous therapy. When such a needle is inserted into soft tissue, it bends due to the asymmetric geometry of the bevel tip. This insertion with bending is not completely repeatable. We characterize the deviations in needle tip pose (position and orientation) by performing repeated needle insertions into artificial tissue. The base of the needle is pushed at a constant speed without rotating, and the covariance of the distribution of the needle tip pose is computed from experimental data. We develop the closed-form equations to describe how the covariance varies with different model parameters. We estimate the model parameters by matching the closed-form covariance and the experimentally obtained covariance. In this work, we use a needle model modified from a previously developed model with two noise parameters. The modified needle model uses three noise parameters to better capture the stochastic behavior of the needle insertion. The modified needle model provides an improvement of the covariance error from 26.1% to 6.55%.
Nonholonomic Modeling of Needle Steering
The International Journal of Robotics Research, 2006
As a flexible needle with a bevel tip is pushed through soft tissue, the asymmetry of the tip causes the needle to bend. We propose that, by using nonholonomic kinematics, control, and path planning, an appropriately designed needle can be steered through tissue to reach a specified 3D target. Such steering capability could enhance targeting accuracy and may improve outcomes for percutaneous therapies, facilitate research on therapy effectiveness, and eventually enable new minimally invasive techniques. In this paper, we consider a first step toward active needle steering: design and experimental validation of a nonholonomic model for steering flexible needles with bevel tips. The model generalizes the standard three degree-of-freedom (DOF) nonholonomic unicycle and bicycle models to 6 DOF using Lie group theory. Model parameters are fit using experimental data, acquired via a robotic device designed for the specific purpose of inserting and steering a flexible needle. The experiments quantitatively validate the bevel-tip needle steering model, enabling future research in flexible needle path planning, control, and simulation.
Cyclic Motion Control for Programmable Bevel-Tip Needle 3D Steering: A Simulation Study
2018
Flexible, steerable, soft needles are desirable in Minimally Invasive Surgery to achieve complex trajectories while maintaining the benefits of percutaneous intervention compared to open surgery. One such needle is the multi-segment Programmable Bevel-tip Needle (PBN), which is inspired by the mechanical design of the ovipositor of certain wasps. PBNs can steer in 3D whilst minimizing the force applied to the surrounding substrate, due to the cyclic motion of the segments. Taking inspiration also from the control strategy of the wasp to perform insertions and lay their eggs, this paper presents the design of a cyclic controller that can steer a PBN to produce a desired trajectory in 3D. The performance of the controller is demonstrated in simulation in comparison to that of a direct controller without cyclic motion. It is shown that, while the same steering curvatures can be attained by both controllers, the time taken to achieve the configuration is longer for the cyclic controller, leading to issues of potential under-steering and longer insertion times.
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