Ali Asadian

A Novel Force Modeling Scheme for Needle Insertion Using Multiple Kalman Filters

In this paper, the interaction force between a surgical needle and soft tissue is studied. The force is modeled using a novel nonlinear dynamic model. Encouraged by the LuGre model for representing friction forces, the proposed model captures all stages of needle-tissue interaction, including puncture, cutting, and friction forces. An estimation algorithm for identifying the parameters of the model is presented. This online approach, which is based on sequential extended Kalman filtering, enables us to characterize the total contact force using an efficient mathematical model. The algorithm compares the axial force measured at the needle base with its expected value and then adapts the model parameters to represent the actual interaction force. While the nature of this problem is very complex, the use of multiple Kalman filters makes the system highly adaptable for capturing the force evolution during an interventional procedure in standard operating conditions. To evaluate the performance of our model, experiments were performed on artificial phantoms.

Position control of concentric-tube continuum robots using a modified Jacobian-based approach

Concentric-tube robots can offer dexterous positioning even in a small constrained environment. This technology turns out to be beneficial in many classes of minimally invasive procedures. However, one of the barriers to the practical use of a concentric-tube robot is the design of a real-time control scheme. In previous work by the authors, a computationally efficient torsionally compliant kinematic model of a concentric-tube robot was developed. Using this computationally fast technique and deriving the robots Jacobian, a new position control approach is proposed in this paper. This mechanism provides computational efficiency as well as good tracking accuracy. To evaluate the performance, experiments were conducted, and the results obtained demonstrate the feasibility of enabling the robots tip to perform trajectory tracking in real time.

An analytical model for deflection of flexible needles during needle insertion

This paper presents a new needle deflection model that is an extension of prior work in our group based on the principles of beam theory. The use of a long flexible needle in percutaneous interventions necessitates accurate modeling of the generated curved trajectory when the needle interacts with soft tissue. Finding a feasible model is important in simulators with applications in training novice clinicians or in path planners used for needle guidance. Using intra-operative force measurements at the needle base, our approach relates mechanical and geometric properties of needle-tissue interaction to the net amount of deflection and estimates the needle curvature. To this end, tissue resistance is modeled by introducing virtual springs along the needle shaft, and the impact of needle-tissue friction is considered by adding a moving distributed external force to the bending equations. Cutting force is also incorporated by finding its equivalent sub-boundary conditions. Subsequently, the closed-from solution of the partial differential equations governing the planar deflection is obtained using Greens functions. To evaluate the performance of our model, experiments were carried out on artificial phantoms.

Robot-Assisted Needle Steering Using a Control Theoretic Approach

This paper presents a new 2D motion planner for steering flexible needles inside relatively rigid tissue. This approach uses a nonholonomic system approach, which models tissue-needle interaction, and formulates the problem as a Markov Decision Process that is solvable using infinite horizon Dynamic Programming. Unlike conventional numerical solvers such as the value iterator which inherently suffers from the curse of dimensionality for processing large-scale models, partitioned-based solvers show promising numerical performance. Given the locations of the obstacles and the targeted area, the proposed solver provides a descent solution where high spatial or angular resolution is required. As theoretically expected, it is shown how prioritized partitioning increases computational performance compared to the generic value iteration which has been used in an existing steering approach. Starting from any initial condition in the workspace, this method enables the needle to reach its target and avoid collisions with obstacles through selecting the shortest path with the least number of turning points thereby causing less trauma. In this paper, emphasis is given to the control aspects of the problem rather than to biomedical issues. Experimental results using an artificial phantom show that the method is capable of positioning the needle tip at the targeted area with an acceptable level of accuracy.

Dynamics of Translational Friction in Needle–Tissue Interaction During Needle Insertion

In this study, a distributed approach to account for dynamic friction during needle insertion in soft tissue is presented. As is well known, friction is a complex nonlinear phenomenon. It appears that classical or static models are unable to capture some of the observations made in systems subjected to significant frictional effects. In needle insertion, translational friction would be a matter of importance when the needle is very flexible, or a stop-and-rotate motion profile at low insertion velocities is implemented, and thus, the system is repeatedly transitioned from a pre-sliding to a sliding mode and vice versa. In order to characterize friction components, a distributed version of the LuGre model in the state-space representation is adopted. This method also facilitates estimating cutting force in an intra-operative manner. To evaluate the performance of the proposed family of friction models, experiments were conducted on homogeneous artificial phantoms and animal tissue. The results illustrate that our approach enables us to represent the main features of friction which is a major force component in needle–tissue interaction during needle-based interventions.

A distributed model for needle-tissue friction in percutaneous interventions

This paper presents a new approach to account for distributed friction in needle insertion in soft tissue. As is well known, friction is a complex nonlinear phenomenon, and it appears that classical or static models are unable to capture some of the observations in systems subject to significant frictional effects. To characterize dynamic features when the needle is very flexible and friction plays an important role in bending mechanics or when a stop-and-start planning scenario is implemented at low insertion velocities, a distributed LuGre model can be adopted. Experimental results using an artificial phantom illustrate that the proposed method is capable of representing the main features of friction which is a major force component in needle-tissue interaction during percutaneous interventions.

A compact dynamic force model for needle-tissue interaction

In this paper, the interaction force between a surgical needle and soft tissue is studied. The force is modeled using nonlinear dynamics based on a modified LuGre model that captures all stages of needle-tissue interaction including puncture, cutting, and friction forces. An estimation algorithm for identifying the associated parameters is then presented. This approach, which is based on extended Kalman filtering (EKF), enables us to characterize the interaction with a mathematical model in the force domain. It compares the axial force measured at the needle base with its expected value and then adapts the model parameters to represent the actual interaction. To evaluate the performance of our model, experiments were performed on an artificial phantom.

Analysis of needle-tissue friction during vibration-assisted needle insertion

In this paper, a vibration-assisted needle insertion technique has been proposed in order to reduce needle-tissue friction. The LuGre friction model was employed as a basis for the current study and the model was extended and analyzed to include the impact of high-frequency vibration on translational friction. Experiments were conducted to evaluate the role of insertion speed as well as vibration frequency on frictional effects. In the experiments conducted, an 18 GA brachytherapy needle was vibrated and inserted into an ex-vivo soft tissue sample using a pair of amplified piezoelectric actuators. Analysis demonstrates that the translational friction can be reduced by introducing a vibratory low-amplitude motion onto a regular insertion profile, which is usually performed at a constant rate.

Design and Performance Evaluation of a Prototype MRF-Based Haptic Interface for Medical Applications

This paper describes the construction and stability and transparency evaluation of a prototype two degrees-of-freedom (DoF) haptic interface, which takes advantage of magneto-rheological fluid (MRF)-based clutches for actuation. These small-scale clutches were designed in our lab, and their evaluation were reported previously [1], [2]. MRF-based actuators exhibit superior characteristics, which can significantly contribute to transparency and stability of haptic devices. Based on these actuators, a distributed antagonistic configuration is used to develop the 2-DoF haptic interface. This device is incorporated in a master-slave teleoperation setup intended for medical percutaneous interventions and soft-tissue palpation. Preliminary studies on the stability and transparency of the haptic interface in this setup using phantom and ex vivo samples show the great potential of MRF-based actuators for integration in haptic devices that require reliable, safe, accurate, highly transparent, and stable force reflection.

Accelerated needle steering using partitioned value iteration

This paper presents a fast 2D motion planner for steering flexible needles inside relatively rigid tissue. This approach exploits a nonholonomic system approach, which models tissue-needle interaction, and formulates the problem as a Markov Decision Process that is solvable using infinite horizon Dynamic Programming. Starting from any initial condition defined in the workspace, this method calculates a set of control actions that enables the needle to reach the target and avoid collisions with obstacles. Unlike conventional solvers, e.g. the value iterator, which suffers from the curse of dimensionality, partitioned-based solvers show promising numerical performance. Given a segmented image of a workspace including the locations of the obstacles, the target and the entry point, the partitioned-based solver provides a descent solution where high resolution is required. It is shown in this paper how prioritized partitioning increases computational performance of the current DP-based solutions for the purpose of off-line path planning. By default, our planner selects the path with the least number of turning points while maintaining minimum insertion length, which leads to the least damage to tissue. In this paper, more emphasis is given to the control aspects of the problem rather than the corresponding biomedical issues.