Image-Based Force Estimation and Haptic Rendering For Robot-Assisted Cardiovascular Intervention

Clinical studies have indicated that the loss of haptic perception is the prime limitation of robot-assisted cardiovascular intervention technology, hindering its global adoption. It causes compromised situational awareness for the surgeon during the intervention and may lead to health risks for the patients. This doctoral research was aimed at developing technology for addressing the limitation of the robot-assisted intervention technology in the provision of haptic feedback. The literature review showed that sensor-free force estimation (haptic cue) on endovascular devices, intuitive surgeon interface design, and haptic rendering within the surgeon interface were the major knowledge gaps. For sensor-free force estimation, first, an image-based force estimation methods based on inverse finite-element methods (iFEM) was developed and validated. Next, to address the limitation of the iFEM method in real-time performance, an inverse Cosserat rod model (iCORD) with a computationally efficient solution for endovascular devices was developed and validated. Afterward, the iCORD was adopted for analytical tip force estimation on steerable catheters. The experimental studies confirmed the accuracy and real-time performance of the iCORD for sensor-free force estimation. Afterward, a wearable drift-free rotation measurement device (MiCarp) was developed to facilitate the design of an intuitive surgeon interface by decoupling the rotation measurement from the insertion measurement. The validation studies showed that MiCarp had a superior performance for spatial rotation measurement compared to other modalities. In the end, a novel haptic feedback system based on smart magnetoelastic elastomers was developed, analytically modeled, and experimentally validated. The proposed haptics-enabled surgeon module had an unbounded workspace for interventional tasks and provided an intuitive interface. Experimental validation, at component and system levels, confirmed the usability of the proposed methods for robot-assisted intervention systems

Online Disturbance Estimation for Improving Kinematic Accuracy in Continuum Manipulators

Continuum manipulators are flexible robots which undergo continuous deformation as they are actuated. To describe the elastic deformation of such robots, kinematic models have been developed and successfully applied to a large variety of designs and to various levels of constitutive stiffness. Independent of the design, kinematic models need to be calibrated to best describe the deformation of the manipulator. However, even after calibration, unmodeled effects such as friction, nonlinear elastic and/or spatially varying material properties as well as manufacturing imprecision reduce the accuracy of these models. In this letter, we present a method for improving the accuracy of kinematic models of continuum manipulators through the incorporation of orientation sensor feedback. We achieve this through the use of a “disturbance wrench,” which is used to compensate for these unmodeled effects, and is continuously estimated based on orientation sensor feedback as the robot moves through its workspace. The presented method is applied to the HydroJet, a waterjet-actuated soft continuum manipulator, and shows an average of 40% reduction in root mean square position and orientation error in the two most common types of kinematic models for continuum manipulators, a Cosserat rod model and a pseudo-rigid body model

Stiffness Imaging With a Continuum Appendage: Real-Time Shape and Tip Force Estimation From Base Load Readings

In this paper, we propose benefiting from load readings at the base of a continuum appendage for real-time forward integration of Cosserat rod model with application in configuration and tip load estimation. The application of this method is successfully tested for stiffness imaging of a soft tissue, using a 3-DOF hydraulically actuated braided continuum appendage. Multiple probing runs with different actuation pressures are used for mapping the tissue surface shape and directional linear stiffness, as well as detecting non-homogeneous regions, e.g. a hard nodule embedded in a soft silicon tissue phantom. Readings from a 6-axis force sensor at the tip is used for comparison and verification. As a result, the tip force is estimated with 0.016-0.037 N (7-20%) mean error in the probing and 0.02-0.1 N (6-12%) in the indentation direction, 0.17 mm (14%) mean error is achieved in estimating the surface profile, and 3.4-15 [N/m] (10-16%) mean error is observed in evaluating tissue directional stiffness, depending on the appendage actuation. We observed that if the appendage bends against the slider motion (toward the probing direction), it provides better horizontal stiffness estimation and better estimation in the perpendicular direction is achieved when it bends toward the slider motion (against the probing direction). In comparison with a rigid probe, ≈ 10 times smaller stiffness and ≈ 7 times larger mean standard deviation values were observed, suggesting the importance of a probe stiffness in estimation the tissue stiffness

Modeling and Force Estimation of Cardiac Catheters for Haptics-enabled Tele-intervention

Robot-assisted cardiovascular intervention (RCI) systems have shown success in reducing the x-ray exposure to surgeons and patients during cardiovascular interventional procedures. RCI systems typically are teleoperated systems with leader-follower architecture. With such system architecture, the surgeon is placed out of the x-ray exposure zone and uses a console to control the robot remotely. Despite its success in reducing x-ray exposure, clinicians have identified the lack of force feedback as to its main technological limitation that can lead to vascular perforation of the patient’s vessels and even their death. The objective of this thesis was to develop, verify, and validate mechatronics technology for real-time accurate and robust haptic feedback rendering for RCI systems. To attain the thesis objective, first, a thorough review of the state-of-the-art clinical requirements, modeling approaches and methods, and current knowledge gaps for the provision of force feedback for RCI systems was performed. Afterward, a real-time tip force estimation method based on image-based shape-sensing and learning-from-simulation was developed and validated. The learning-based model was fairly accurate but required a large database for training which was computationally expensive. Next, a new mechanistic model, i.e., finite arc method (FAM) for soft robots was proposed, formulated, solved, and validated that allowed for fast and accurate modeling of catheter deformation. With FAM, the required training database for the proposed learning-from-simulation method would be generated with high speed and accuracy. In the end, to robustly relay the estimated forces from real-time imaging from the follower robot to the leader haptic device, a novel impedance-based force feedback rendering modality was proposed and implemented on a representative teleoperated RCI system for experimental validation. The proposed method was compared with the classical direct force reflection method and showed enhanced stability, robustness, and accuracy in the presence of communication disruption. The results of this thesis showed that the performance of the proposed integrated force feedback rendering system was in fair compliance with the clinical requirements and had superior robustness compared to the classical direct force reflection method

Modelling and simulation of flexible instruments for minimally invasive surgical training in virtual reality

Improvements in quality and safety standards in surgical training, reduction in training hours and constant technological advances have challenged the traditional apprenticeship model to create a competent surgeon in a patient-safe way. As a result, pressure on training outside the operating room has increased. Interactive, computer based Virtual Reality (VR) simulators offer a safe, cost-effective, controllable and configurable training environment free from ethical and patient safety issues. Two prototype, yet fully-functional VR simulator systems for minimally invasive procedures relying on flexible instruments were developed and validated. NOViSE is the first force-feedback enabled VR simulator for Natural Orifice Transluminal Endoscopic Surgery (NOTES) training supporting a flexible endoscope. VCSim3 is a VR simulator for cardiovascular interventions using catheters and guidewires. The underlying mathematical model of flexible instruments in both simulator prototypes is based on an established theoretical framework – the Cosserat Theory of Elastic Rods. The efficient implementation of the Cosserat Rod model allows for an accurate, real-time simulation of instruments at haptic-interactive rates on an off-the-shelf computer. The behaviour of the virtual tools and its computational performance was evaluated using quantitative and qualitative measures. The instruments exhibited near sub-millimetre accuracy compared to their real counterparts. The proposed GPU implementation further accelerated their simulation performance by approximately an order of magnitude. The realism of the simulators was assessed by face, content and, in the case of NOViSE, construct validity studies. The results indicate good overall face and content validity of both simulators and of virtual instruments. NOViSE also demonstrated early signs of construct validity. VR simulation of flexible instruments in NOViSE and VCSim3 can contribute to surgical training and improve the educational experience without putting patients at risk, raising ethical issues or requiring expensive animal or cadaver facilities. Moreover, in the context of an innovative and experimental technique such as NOTES, NOViSE could potentially facilitate its development and contribute to its popularization by keeping practitioners up to date with this new minimally invasive technique.Open Acces

Design and Modeling of Multi-Arm Continuum Robots

Continuum robots are snake-like systems able to deliver optimal therapies to pathologies deep inside the human cavity by following 3D complex paths. They show promise when anatomical pathways need to be traversed thanks to their enhanced flexibility and dexterity and show advantages when deployed in the field of single-port surgery. This PhD thesis concerns the development and modelling of multi-arm and hybrid continuum robots for medical interventions. The flexibility and steerability of the robot’s end-effector are achieved through concentric tube technology and push/pull technology. Medical robotic prototypes have been designed as proof of concepts and testbeds of the proposed theoretical works.System design considers the limitations and constraints that occur in the surgical procedures for which the systems were proposed for. Specifically, two surgical applications are considered. Our first prototype was designed to deliver multiple tools to the eye cavity for deep orbital interventions focusing on a currently invasive intervention named Optic Nerve Sheath Fenestration (ONSF). This thesis presents the end-to-end design, engineering and modelling of the prototype. The developed prototype is the first suggested system to tackle the challenges (limited workspace, need for enhanced flexibility and dexterity, danger for harming tissue with rigid instruments, extensive manipulation of the eye) arising in ONSF. It was designed taking into account the clinical requirements and constraints while theoretical works employing the Cosserat rod theory predict the shape of the continuum end-effector. Experimental runs including ex vivo experimental evaluations, mock-up surgical scenarios and tests with and without loading conditions prove the concept of accessing the eye cavity. Moreover, a continuum robot for thoracic interventions employing push/pull technology was designed and manufactured. The developed system can reach deep seated pathologies in the lungs and access regions in the bronchial tree that are inaccessible with rigid and straight instruments either robotically or manually actuated. A geometrically exact model of the robot that considers both the geometry of the robot and mechanical properties of the backbones is presented. It can predict the shape of the bronchoscope without the constant curvature assumption. The proposed model can also predict the robot shape and micro-scale movements accurately in contrast to the classic geometric model which provides an accurate description of the robot’s differential kinematics for large scale movements

Teleoperation and Contact Detection of a Waterjet-Actuated Soft Continuum Manipulator for Low-Cost Gastroscopy

Gastric cancer is the third leading cause of cancer deaths worldwide, with most new cases occurring in low and middle income countries, where access to screening programs is hindered by the high cost of conventional endoscopy. The waterjet-actuated HydroJet endoscopic platform was developed as a low-cost, disposable alternative for inspection of the gastric cavity in low-resource settings. In this work, we present a teleoperation scheme and contact detection algorithm that work together to enable intuitive teleoperation of the HydroJet within the confined space of the stomach. Using a geometrically accurate stomach model and realistic anatomical inspection targets, we demonstrate that, using these methods, a novice user can complete a gastroscopy in approximately the same amount of time with the HydroJet as with a conventional endoscope

Modeling, Analysis, Force Sensing and Control of Continuum Robots for Minimally Invasive Surgery

This dissertation describes design, modeling and application of continuum robotics for surgical applications, specifically parallel continuum robots (PCRs) and concentric tube manipulators (CTMs). The introduction of robotics into surgical applications has allowed for a greater degree of precision, less invasive access to more remote surgical sites, and user-intuitive interfaces with enhanced vision systems. The most recent developments have been in the space of continuum robots, whose exible structure create an inherent safety factor when in contact with fragile tissues. The design challenges that exist involve balancing size and strength of the manipulators, controlling the manipulators over long transmission pathways, and incorporating force sensing and feedback from the manipulators to the user. Contributions presented in this work include: (1) prototyping, design, force sensing, and force control investigations of PCRs, and (2) prototyping of a concentric tube manipulator for use in a standard colonoscope. A general kinetostatic model is presented for PCRs along with identification of multiple physical constraints encountered in design and construction. Design considerations and manipulator capabilities are examined in the form of matrix metrics and ellipsoid representations. Finally, force sensing and control are explored and experimental results are provided showing the accuracy of force estimates based on actuation force measurements and control capabilities. An overview of the design requirements, manipulator construction, analysis and experimental results are provided for a CTM used as a tool manipulator in a traditional colonoscope. Currently, tools used in colonoscopic procedures are straight and exit the front of the scope with 1 DOF of operation (jaws of a grasper, tightening of a loop, etc.). This research shows that with a CTM deployed, the dexterity of these tools can be increased dramatically, increasing accuracy of tool operation, ease of use and safety of the overall procedure. The prototype investigated in this work allows for multiple tools to be used during a single procedure. Experimental results show the feasibility and advantages of the newly-designed manipulators