Observations and models for needle-tissue interactions

The asymmetry of a bevel-tip needle results in the needle naturally bending when it is inserted into soft tissue. In this study we present a mechanics-based model that calculates the deflection of the needle embedded in an elastic medium. Microscopic observations for several needle- gel interactions were used to characterize the interactions at the bevel tip and along the needle shaft. The model design was guided by microscopic observations of several needle- gel interactions. The energy-based model formulation incor- porates tissue-specific parameters such as rupture toughness, nonlinear material elasticity, and interaction stiffness, and needle geometric and material properties. Simulation results follow similar trends (deflection and radius of curvature) to those observed in macroscopic experimental studies of a robot- driven needle interacting with different kinds of gels. These results contribute to a mechanics-based model of robotic needle steering, extending previous work on kinematic models

Characterization of a pre-curved needle for use in distal tip manipulation mechanism

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 59-61).The knowledge and technical expertise required for the development of telerobotic systems capable of needle distal tip manipulation is the focus of this thesis. An extensive prior literature review was conducted to examine (1) the current medical devices available to pulmonary radiologists and (2) the current steerable mechanism state of the art. Interviews were also conducted with interventional radiology and cardiology physicians at the Massachusetts General Hospital to define the mechanism functional requirements for a telerobotic system and a first order analysis was undertaken to evaluate three strategies. The selected strategy was based on the concept of deploying a flexible pre-curved stylet from a concentric straight cannula. Analytical models were developed to (1) understand what material properties are required to recover from the imposed strains, (2) compare stylet stiffness relative to each other and the cannulas, and (3) calculate the deployment and retraction forces required for moving the stylet relative to the cannula. Sixteen Nitinol stylets were prototyped and experiments were performed with four different diameter cannulas and an experimental setup and methodology was developed to measure the deployment and retraction forces. The data collected for 48 permutations of stylet diameter, stylet bend radius, and cannula gauge were compared to the analytical model. Retraction forces were measured between .277 and 13.9N, and deployment forces were measured between .191 and 6.95N. For a given cannula it was found that force increases as stylet diameter increases and bend radius decreases. The analytical model better matched the experimental retraction and deployment measurements for the smaller stylet diameters (0.508 and 0.635 mm) with low friction, retraction and deployment forces. It was found that the retraction and deployment force does not necessarily increase or decrease with cannula diameter and it was found that the stylets drawn through the 16 gauge cannula consistently had the lowest deployment and retraction forces recorded across the four cannulas tested. Ultimately, the experimental and analytical tools developed in this thesis helped us select appropriate needle materials and mechanism components for use in a telerobotic system that is under development.by Jeremy Contini Franklin.S.B

Design and evaluation of a computed tomography (CT)-compatible needle insertion device using an electromagnetic tracking system and CT images

Purpose Percutaneous needle insertion procedures are commonly used for diagnostic and therapeutic purposes. Although current technology allows accurate localization of lesions, they cannot yet be precisely targeted. Lung cancer is the most common cause of cancer-related death, and early detection reduces the mortality rate. Therefore, suspicious lesions are tested for diagnosis by performing needle biopsy. Methods In this paper, we have presented a novel computed tomography (CT)-compatible needle insertion device (NID). The NID is used to steer a flexible needle (ϕ0.55mm ϕ0.55mm) with a bevel at the tip in biological tissue. CT images and an electromagnetic (EM) tracking system are used in two separate scenarios to track the needle tip in three-dimensional space during the procedure. Our system uses a control algorithm to steer the needle through a combination of insertion and minimal number of rotations. Results Noise analysis of CT images has demonstrated the compatibility of the device. The results for three experimental cases (case 1: open-loop control, case 2: closed-loop control using EM tracking system and case 3: closed-loop control using CT images) are presented. Each experimental case is performed five times, and average targeting errors are 2.86±1.14 2.86±1.14, 1.11±0.14 1.11±0.14 and 1.94 0.63mm 1.94±0.63mm for case 1, case 2 and case 3, respectively. Conclusions The achieved results show that our device is CT-compatible and it is able to steer a bevel-tipped needle toward a target. We are able to use intermittent CT images and EM tracking data to control the needle path in a closed-loop manner. These results are promising and suggest that it is possible to accurately target the lesions in real clinical procedures in the future

A mechanics-based model for 3D steering of programmable bevel-tip needles

We present a model for the steering of programmable bevel-tip needles, along with a set of experiments demonstrating the 3D steering performance of a new, clinically viable, 4-segment, pre-production prototype. A multi-beam approach, based on Euler-Bernoulli beam theory, is used to model the novel multi-segment design of these needles. Finite element simulations for known loads are used to validate the multi-beam deflection model. A clinically sized (2.5 mm outer diameter), 4-segment programmable bevel-tip needle, manufactured by extrusion of a medical-grade polymer, is used to conduct an extensive set of experimental trials to evaluate the steering model. For the first time, we demonstrate the ability of the 4-segment needle design to steer in any direction with a maximum achievable curvature of 0.0192±0.0014 mm⁻¹. Finite element simulations confirm that the multi-beam approach produces a good model fit for tip deflections, with a root-mean-square deviation (RMSD) in modeled tip deflection of 0.2636 mm. We perform a parameter optimization to produce a best-fit steering model for the experimental trials, with a RMSD in curvature prediction of 1.12×10⁻³ mm⁻¹

A robotic flexible drill and its navigation system for total hip arthroplasty

This paper presents a robotic flexible drill and its navigation system for Total Hip Arthroplasty (THA). The new robotic system provides an unprecedented and unique capability to perform curved femoral milling under the guidance of a multimodality navigation system. The robotic system consists of three components. Firstly, a flexible drill manipulator comprises multiple rigid segments that act as a sheath to a flexible shaft with a drill/burr attached to the end. The second part of the robotic system is a hybrid tracking system that consists of an optical tracking system and a position tracking system. Optical tracking units are used to track the surgical objects and tools outside the drilling area, while a rotary encoder placed at each joint of the sheath is synchronized to provide the position information for the flexible manipulator with its virtual object. Finally, the flexible drill is integrated into a computer-aided navigation system. The navigation system provides real time guidance to a surgeon during the procedure. The flexible drill system is then able to implement Total Hip Arthroplasty by bone milling. The final section of this paper is an evaluation of the flexible and steerable drill and its navigation system for femoral bone milling in sawbones

Robotically Steered Needles: A Survey of Neurosurgical Applications and Technical Innovations

This paper surveys both the clinical applications and main technical innovations related to steered needles, with an emphasis on neurosurgery. Technical innovations generally center on curvilinear robots that can adopt a complex path that circumvents critical structures and eloquent brain tissue. These advances include several needle-steering approaches, which consist of tip-based, lengthwise, base motion-driven, and tissue-centered steering strategies. This paper also describes foundational mathematical models for steering, where potential fields, nonholonomic bicycle-like models, spring models, and stochastic approaches are cited. In addition, practical path planning systems are also addressed, where we cite uncertainty modeling in path planning, intraoperative soft tissue shift estimation through imaging scans acquired during the procedure, and simulation-based prediction. Neurosurgical scenarios tend to emphasize straight needles so far, and span deep-brain stimulation (DBS), stereoelectroencephalography (SEEG), intracerebral drug delivery (IDD), stereotactic brain biopsy (SBB), stereotactic needle aspiration for hematoma, cysts and abscesses, and brachytherapy as well as thermal ablation of brain tumors and seizure-generating regions. We emphasize therapeutic considerations and complications that have been documented in conjunction with these applications

Characterization of a pre-curved stylet distal tip manipulation mechanism for use in volume targeting

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 52).The characterization of the volume targeting capabilities of a telerobotic device capable of needle distal tip manipulation with a pre-curved needle is the focus of this thesis. The concept of deploying a pre-curved stylet from a concentric stiff cannula that is capable of both translational and rotational motions allows the device to achieve targeting of volumes through a single needle insertion into a soft medium. Each mechanism component was analyzed for its motion, and separate functional requirements were determined for experiments to characterize its accuracy and repeatability. Three main areas of mechanical studies were selected for experimentation: (1) accuracy and repeatability of the robot drive mechanisms; (2) 3D experiments measured the positional accuracies of the device in being able to command the cannula or stylet tips to travel to the desired location input into the control box; (3) 2D experiments in body tissue simulating ballistics gelatin analyzed the accuracy and repeatability of the device in being able to target a small volume inside simulated surgical environments in one plane, as well as the potential effects the gelatin may have had on the stylets' travel paths. Each set of experimental protocols and setup were specifically designed to target the characterization of that mechanism or component of the device. A kinematic model was used as a basis of comparison for the two latter experiments. The robot drive mechanism has a fundamental driving repeatability of 0.209mm in cannula axial translation, 0.034mm in stylet axial translation and 0.2200 in cannula rotation. For the 0.838mm diameter 30mm radius of curvature stylet, the stylet has an actual radius of curvature of 31.72mm as determined through a scan measurement. The tip positions experiments in the CMM and gel yielded radii of curvature changes of - 1.461mm or -4.606% between the CMM data and the actual measured stylet, and +1.202mm or +3.789% between the gel data and the stylet. 2D volume targeting experiments yielded an average distance of 1.8822mm + 0.2628mm between the measured stylet tip positions and the model based calculated positions. The stylet with the highest targeting accuracy and repeatability was the 0.838mm diameter 20mm radius of curvature stylet with a targeting accuracy of 1.2760mm ± 0.7256mm, making it the ideal stylet for use in volume targeting procedures.by Hao Ding.S.B