In the development of telemanipulated surgical robots, a class of continuum robots known as concentric tube robots has drawn particular interest for clinical applications in which space is a major limitation. One such application is transnasal surgery, which is used to access surgical sites in the sinuses and at the skull base. Current techniques for performing these procedures require surgeons to maneuver multiple rigid tools through the narrow confines of the nasal passages, leaving them with limited dexterity at the surgical site. In this article, we present a complete robotic system for transnasal surgery featuring concentric tube manipulators. It illustrates a bagging concept for sterility, and intraoperatively interchangeable instruments that work in conjunction with it, which were developed with operating room workflow compatibility in mind. The system also includes a new modular, portable surgeon console, a variable view-angle endoscope to facilitate surgical field visualization, and custom motor control electronics. Furthermore, we demonstrate elastic instability avoidance for the first time on a physical prototype in a geometrically accurate surgical scenario, which facilitates use of higher curvature tubes than could otherwise be used safely in this application. From a surgical application perspective, this article presents the first robotic approach to removing tumors growing behind the eyes in the orbital apex region, which has not been attempted previously with a surgical robot.

Concentric tube robots consist of nested sets of precurved elastic tubes that bend and deform one another when they are translated and rotated with respect to each other, resulting in tentacle-like motion. Concentric tube robots are needle-sized devices, which makes them promising instruments for minimally-invasive surgical tasks. Their potential has motivated a significant amount of research focused on modeling their behavior, designing their actuation systems and shape to meet application requirements, controlling them in surgical environments, planning their motions in constrained anatomy, and sensing their shape in space for realtime feedback. In this chapter, we present an overview of concentric tube robots’ development for use as both steerable needles and robotic manipulators.

Designing a continuum robot’s geometry, sensing its shape/state in space, and planning collision-free trajectories that meet the needs of an application were initially thought of as decoupled problems for continuum robots. However, a body of literature is beginning to emerge showing advantages in solving various combinations of two of these three problems simultaneously. In this paper we argue that all three of these problems are fundamentally connected for continuum robots, that the connection can be analyzed using statistical state estimation, and that considering the three problems simultaneously can lead to better overall solutions. We provide examples for concentric-tube continuum robots.

We introduce a method to optimize on a patient-specific basis the kinematic design of the Continuum Reconfigurable Incisionless Surgical Parallel (CRISP) robot, a needlediameter medical robot based on a parallel structure that is capable of performing minimally invasive procedures. Our objective is to maximize the ability of the robot's tip camera to view tissue surfaces in constrained spaces. The kinematic design of the CRISP robot, which greatly influences its ability to perform a task, includes parameters that are fixed before the procedure begins, such as entry points into the body and parallel structure connection points. We combine a global stochastic optimization algorithm, Adaptive Simulated Annealing (ASA), with a motion planner designed specifically for the CRISP robot. ASA facilitates exploration of the robot's design space while the motion planner enables evaluation of candidate designs based on their ability to successfully view target regions on a tissue surface. By leveraging motion planning, we ensure that the evaluation of a design only considers motions which do not collide with the patient's anatomy. We analytically show that the method asymptotically converges to a globally optimal solution and demonstrate our algorithm's ability to optimize kinematic designs of the CRISP robot on a patient-specific basis.

A variety of magnetic devices can be manipulated remotely using a single permanent "actuator" magnet positioned in space by a robotic manipulator. This paper presents the spherical-actuator-magnet manipulator (SAMM), which is designed to replace or augment the singularity-prone spherical wrist used by prior permanent-magnet manipulation systems. The SAMM uses three omniwheels to enable holonomic control of a spherical magnet's heading and enable the magnet's instantaneous axis-of-rotation to be set arbitrarily. The SAMM performs closed-loop control of its dipole using field measurements obtained from Hall-effect sensors. We describe the operation and construction of the SAMM, develop and characterize a controller for the SAMM's spherical magnet, and demonstrate remote actuation of an untethered magnetic device in a lumen.

Determining the Validity of Methods Used in Meat Iron Analysis

Continuum Reconfigurable Incisionless Surgical Parallel (CRISP) robots consist of multiple needle-diameter flexible instruments that are assembled into a parallel structure inside the human body. With a camera placed at the tip of one of the instruments, the CRISP robot can be used to inspect anatomical sites in constrained body cavities in a minimally invasive manner. We introduce a motion planner for CRISP robots that computes manipulations of the flexible instruments outside the body such that the camera can visually inspect a user-specified site of clinical interest inside the body. Our sampling-based motion planner ensures avoidance of collisions with anatomical obstacles inside the body, enforces remote-center-of-motion constraints on the instrument's entry points into the body, and efficiently handles the expensive computation of CRISP robot kinematics. We also extend the motion planner to estimate the set of points inside a body cavity that can be visually inspected by the camera of a CRISP robot for a given setup. We demonstrate our method in a simulated endoscopic medical procedure in the pleural space around a lung.

This letter examines shape sensing for a new class of surgical robot that consists of parallel flexible structures that can be reconfigured inside the human body. Known as continuum reconfigurable incisionless surgical parallel (CRISP) robots, these devices provide access to the human body through needle-sized entry points, yet can be configured into trusslike structures capable of dexterous movement and large force application. They can also be reconfigured as needed during a surgical procedure. Since CRISP robots are elastic, they will deform when subjected to external forces or other perturbations. In this letter, we explore how to combine sensor information with mechanics-based models for CRISP robots to estimate their shapes under applied loads. The end result is a shape sensing framework for CRISP robots that will enable future research on control under applied loads, autonomous motion, force sensing, and other robot behaviors.

We propose a new class of robotic device for minimally-invasive surgery that lies at the intersection of continuum, parallel, and reconfigurable robotics. This Continuum Reconfigurable Incisionless Surgical Parallel (CRISP) paradigm involves the use of multiple needle-diameter devices inserted through the skin and assembled into parallel structures inside the body. The parallel structure can be reconfigured inside the patient's body to satisfy changing task requirements such as reaching initially inaccessible locations or modifying mechanical stiffness for manipulation or palpation. Another potential advantage of the CRISP concept is that many small (needle-sized) entry points into the patient may be preferable in terms of both patient healing and cosmesis to the single (or multiple) larger ports needed to admit current surgical robots. This paper presents a mechanics-based model for CRISP forward and inverse kinematics, along with experimental validation.

When designing continuum robots for applications that require sensing, designers are faced with the problems of deciding what sensors to use, where they should be placed, and how best to use the information they provide. In this paper, we describe how a differential representation of a continuum robot's kinematic equations that govern its states (e.g., shape) can be used to simultaneously address these problems under the guidance of statistical state estimation. We identify how state estimation and sensing-system design (i.e., sensor selection and placement) are inherently coupled problems, which leads us to formulate sensing-system design as an optimization problem governed by the results of statistical estimation. As a case-study, the methods described herein are used to design a magnetic sensing system for concentric-tube robots.

Lung cancer is the most deadly form of cancer in part because of the challenges associated with accessing nodules for diagnosis and therapy. Transoral access is preferred to percutaneous access since it has a lower risk of lung collapse, yet many sites are currently unreachable transorally due to limitations with current bronchoscopic instruments. Toward this end, we present a new robotic system for image-guided trans-bronchoscopic lung access. The system uses a bronchoscope to navigate in the airway and bronchial tubes to a site near the desired target, a concentric tube robot to move through the bronchial wall and aim at the target, and a bevel-tip steerable needle with magnetic tracking to maneuver through lung tissue to the target under closed-loop control. In this work, we illustrate the workflow of our system and show accurate targeting in phantom experiments. Ex vivo porcine lung experiments show that our steerable needle can be tuned to achieve appreciable curvature in lung tissue. Lastly, we present targeting results with our system using two scenarios based on patient cases. In these experiments, phantoms were created from patient-specific computed tomography information and our system was used to target the locations of suspicious nodules, illustrating the ability of our system to reach sites that are traditionally inaccessible transorally.

Lung cancer is the most deadly form of cancer, and survival depends on early-stage diagnosis and treatment. Transoral access is preferable to traditional between-the-ribs needle insertion because it is less invasive and reduces risk of lung collapse. Yet many sites in the peripheral zones of the lung or distant from the bronchi cannot currently be accessed transorally, due to the relatively large diameter and lack of sufficient steerablity of current instrumentation. To remedy this, we propose a new robotic system that uses a tendon-actuated device (bronchoscope) as a first stage for deploying a concentric tube robot, which itself is a vehicle through which a bevel steered needle can be introduced into the soft tissue of the lung outside the bronchi. In this paper we present the various components of the system and the workflow we envision for deploying the robot to a target using image guidance. We describe initial validation experiments in which we puncture ex vivo bronchial wall tissue and also target a nodule in a phantom with an average final tip error of 0.72 mm.

This paper demonstrates magnetic three-degree-of-freedom (3-DOF) closed-loop position and 2-DOF open-loop orientation control of a mockup magnetic capsule endoscope in fluid with a single permanent magnet positioned by a commercial 6-DOF robotic manipulator, using feedback of only the 3-DOF capsule position measured by a localization system, with application in capsule endoscopy of a fluid-distended stomach. We analyze the kinematics of magnetic manipulation using a single permanent magnet as the end-effector of a serial-link robot manipulator, and we formulate a control method that enables the capsule’s position and direction to be controlled when the robot manipulator is not in a kinematic singularity, and that sacrifices control over the capsule’s direction to maintain control over the capsule’s position when the manipulator enters a singularity. We demonstrate the method’s robustness to a reduced control rate of 25 Hz, reduced localization rates down to 30 Hz, deviation in the applied magnetic field from that expected, and the presence of manipulator singularities. Five-DOF manipulation of an untethered magnetic device has been previously demonstrated by electromagnetic systems only.

This paper focuses on wire electrical discharge machining (WEDM) of devices made from commercially available sintered neodymium-iron-boron (NdFeB) rare-earth magnets that have been magnetized before machining. We conduct an experimental study to quantify the effects of the voltage and capacitance of an RC-type WEDM machine, as well as the magnet polarity, on slicing rate, mean kerf, and variation in kerf. We find that voltage and capacitance affect slicing rate, that voltage affects mean kerf, that no parameters tested affect the variation in kerf, and that the polarity of the magnet being machined does not affect the machining process. Linear regression is used to fit simple predictive models to the data with good agreement. Further analysis is performed to characterize the loss in permanent magnetization on the surface of the magnet due to heating during the machining process, and it is found that the outer layer of approximately 35 μm in depth is demagnetized when using the highest voltage and capacitance values tested.

In this paper, we examine several magnetic control methods that utilize the fully controllable dipole field generated by the single stationary dipole source. Since the magnetic field generated by a dipole source is nonuniform, it applies both forces and torques to magnetic objects and can be used to manipulate magnetic tools. Recently, the Omnimagnet, a computer-controlled magnetic dipole source capable of varying both its dipole-moment direction and magnitude, was developed to perform magnetic manipulation. The equations and methods are developed generally; therefore, they can be applied to any omnidirectional dipole source, but their effectiveness is demonstrated using the Omnimagnet.

To date, untethered magnetic devices actuated with a single rotating permanent magnet, such as active capsule endoscopes and magnetic microrobots, have been constrained to operate in positions where the rotating dipole field behavior is simple and easy to visualize. In this paper, we show how to generate a rotating magnetic field with any desired rotation axis, for magnetic device actuation, at any device position in space using a single rotating-magnet actuator. The methods presented can control untethered rotating magnetic devices, while the rotating actuator magnet follows trajectories independent of the untethered devices themselves. We demonstrate our methods by actuating rotating magnetic devices in a lumen. Applications include minimally invasive medical tasks requiring an untethered magnetic device to operate in natural lumen pathways of the body (e.g., the gastrointestinal system, the subarachnoid space of the nervous system, or vasculature).

This paper studies the behavior of rotating magnetic microrobots, constructed with a permanent magnet or a soft ferromagnet, when the applied magnetic field rotates faster than a microrobot's step-out frequency (the frequency requiring the entire available magnetic torque to maintain synchronous rotation). A microrobot's velocity dramatically declines when operated above the step-out frequency. As a result, it has generally been assumed that microrobots should be operated beneath their step-out frequency. In this paper, we report and demonstrate properties of a microrobot's behavior above the step-out frequency that will be useful for the design and control of multi-microrobot systems.