Samuel B. Kesner

Position Control of Motion Compensation Cardiac Catheters

Robotic catheters have the potential to revolutionize cardiac surgery by enabling minimally invasive structural repairs within the beating heart. This paper presents an actuated catheter system that compensates for the fast motion of cardiac tissue using 3-D ultrasound image guidance. We describe the design and operation of the mechanical drive system and catheter module and analyze the catheter performance limitations of friction and backlash in detail. To mitigate these limitations, we propose and evaluate mechanical and control-system compensation methods, which include inverse and model-based backlash compensation, to improve the system performance. Finally, in vivo results are presented, which demonstrate that the catheter can track the cardiac tissue motion with less than 1-mm rms error. The ultimate goal of this research is to create a fast and dexterous robotic catheter system that can perform surgery on the delicate structures inside of the beating heart.

Design Principles for Rapid Prototyping Forces Sensors Using 3-D Printing

Force sensors provide critical information about robot manipulators, manufacturing processes, and haptic interfaces. Commercial force sensors, however, are generally not adapted to specific system requirements, resulting in sensors with excess size, cost, and fragility. To overcome these issues, 3-D printers can be used to create components for the quick and inexpensive development of force sensors. Limitations of this rapid prototyping technology, however, require specialized design principles. In this paper, we discuss techniques for rapidly developing simple force sensors, including selecting and attaching metal flexures, using inexpensive and simple displacement transducers, and 3-D printing features to aid in assembly. These design methods are illustrated through the design and fabrication of a miniature force sensor for the tip of a robotic catheter system. The resulting force sensor prototype can measure forces with an accuracy of as low as 2% of the 10 N measurement range.

3D Ultrasound-Guided Motion Compensation System for Beating Heart Mitral Valve Repair

Beating heart intracardiac procedures promise significant benefits for patients, however, the fast motion of the heart poses serious challenges to surgeons. We present a new 3D ultrasound-guided motion (3DUS) compensation system that synchronizes instrument motion with the heart. The system utilizes the fact that the motion of some intracardiac structures, including the mitral valve annulus, is largely constrained to translation along one axis. This allows the development of a real-time 3DUS tissue tracker which we integrate with a 1 degree-of-freedom actuated surgical instrument, real-time 3DUS instrument tracker, and predictive filter to devise a system with synchronization accuracy of 1.8 mm RMSE. User studies involving the deployment of surgical anchors in a simulated mitral annuloplasty procedure demonstrate that the system increases success rates by over 100%. Furthermore, it enables more careful anchor deployment by reducing forces to the tissue by 50% while allowing instruments to remain in contact with the tissue for longer periods.

Force control of flexible catheter robots for beating heart surgery

Recent developments in cardiac catheter technology promise to allow physicians to perform most cardiac interventions without stopping the heart or opening the chest. However, current cardiac devices, including newly developed catheter robots, are unable to accurately track and interact with the fast moving cardiac tissue without applying potentially damaging forces. This paper examines the challenges of implementing force control on a flexible robotic catheter. In particular, catheter friction and backlash must be compensated when controlling tissue interaction forces. Force controller designs are introduced and evaluated experimentally in a number of configurations. The controllers are based on the inner position loop force control approach where the position trajectory is adjusted to achieve a desired force on the target. Friction and backlash compensation improved force tracking up to 86% with residual RMS errors of 0.11 N while following a prerecorded cardiac tissue trajectory with accelerations of up to 3800 mm/s2. This performance provides sufficient accuracy to enable a wide range of beating heart surgical procedures.

Design and control of motion compensation cardiac catheters

Robotic cardiac catheters have the potential to revolutionize heart surgery by extending minimally invasive techniques to complex surgical repairs inside the heart. However, catheter technologies are currently unable to track fast tissue motion, which is required to perform delicate procedures inside a beating heart. This paper proposes an actuated catheter tool that compensates for the motion of heart structures like the mitral valve apparatus by servoing a catheter guidewire inside a flexible sheath. We examine design and operation parameters that affect performance and establish that friction and backlash limit the tracking performance of the catheter system. Based on the results of these experiments and a model of the backlash behavior, we propose and implement compensation methods to improve trajectory tracking performance. The catheter system is evaluated with 3D ultrasound guidance in simulate in vivo conditions. The results demonstrate that with mechanical and control system design improvements, a robotic catheter system can accurately track the fast motion of the human mitral valve.

Discriminating tissue stiffness with a haptic catheter: Feeling the inside of the beating heart

Catheter devices allow physicians to access the inside of the human body easily and painlessly through natural orifices and vessels. Although catheters allow for the delivery of fluids and drugs, the deployment of devices, and the acquisition of the measurements, they do not allow clinicians to assess the physical properties of tissue inside the body due to the tissue motion and transmission limitations of the catheter devices, including compliance, friction, and backlash. The goal of this research is to increase the tactile information available to physicians during catheter procedures by providing haptic feedback during palpation procedures. To accomplish this goal, we have developed the first motion compensated actuated catheter system that enables haptic perception of fast moving tissue structures. The actuated catheter is instrumented with a distal tip force sensor and a force feedback interface that allows users to adjust the position of the catheter while experiencing the forces on the catheter tip. The efficacy of this device and interface is evaluated through a psychophyisical study comparing how accurately users can differentiate various materials attached to a cardiac motion simulator using the haptic device and a conventional manual catheter. The results demonstrate that haptics improves a users ability to differentiate material properties and decreases the total number of errors by 50% over the manual catheter system.

Microsurgical Devices by Pop-Up Book MEMS

The small scale of microsurgery poses significant challenges for developing robust and dexterous tools to grip, cut, and join sub-millimeter structures such as vessels and nerves. The main limitation is that traditional manufacturing techniques are not optimized to create smart, articulating structures in the 0.1–10 mm scale. Pop-up book MEMS is a new fabrication technology that promises to overcome this challenge and enable the monolithic fabrication of complex, articulated structures with an extensive catalog of materials, embedded electrical components, and automated assembly with feature sizes down to 20 microns. In this paper, we demonstrate a proof-of-concept microsurgical gripper and evaluate its performance at the component and device level to characterize its strength and robustness. 1-DOF Flexible hinge joints that constrain motion and allow for out-of-plane actuation were found to resist torsional loads of 22.8±2.15 N·mm per mm of hinge width. Adhesive lap joints that join individual layers in the laminate structure demonstrated a shear strength of 26.8±0.53 N/mm2. The laminate structures were also shown to resist peel loads of 0.72±0.10 N/mm2. Various flexible hinge and adhesive lap components were then designed into an 11-layered structure which ‘pops up’ to realize an articulating microsurgical gripper that includes a cable-driven mechanism for gripping actuation and a flexural return spring to passively open the gripper. The gripper prototype, with final weight of 200 mg, overall footprint of 18 mm by 7.5 mm, and features as small as 200 microns, is able to deftly manipulate objects 100 times is own weight at the required scale, thus demonstrating its potential for use in microsurgery.Copyright

Simple and effective ultrasound needle guidance system

In this paper, we describe our prototype of an ultrasound guidance system to address the need for an easy-to-use, cost-effective, and portable technology to improve ultrasound-guided procedures. The system consists of a lockable, articulating needle guide that attaches to an ultrasound probe and a user-interface that provides real-time visualization of the predicted needle trajectory overlaid on the ultrasound image. Our needle guide ensures proper needle alignment with the ultrasound imaging plane. Moreover, the calculated needle trajectory is superimposed on the real-time ultrasound image, eliminating the need for the practitioner to estimate the target trajectory, and thereby reducing injuries from needle readjustment. Finally, the guide is lockable to prevent needle deviation from the desired trajectory during insertion. This feature will also allow the practitioner to free one hand to complete simple tasks that usually require a second practitioner to perform. Overall, our system eliminates the experience required to develop the fine hand movement and dexterity needed for traditional ultrasound-guided procedures. The system has the potential to increase efficiency, safety, quality, and reduce costs for a wide range of ultrasound-guided procedures. Furthermore, in combination with portable ultrasound machines, this system will enable these procedures to be more easily performed by unskilled practitioners in non-ideal situations such as the battlefield and other disaster relief areas.

Ultrasound servoing of catheters for beating heart valve repair

Robotic cardiac catheters have the potential to revolutionize heart surgery by extending minimally invasive techniques to complex surgical repairs inside the heart. However, catheter technologies are currently unable to track fast tissue motion, which is required to perform delicate procedures inside a beating heart. This paper presents an actuated catheter tool that compensates for the motion of heart structures like the mitral valve apparatus by servoing a catheter guidewire inside a flexible sheath. We examine design and operation parameters and establish that friction and backlash limit the tracking performance of the catheter system. Based on the results of these experiments, we implement compensation methods to improve trajectory tracking. The catheter system is then integrated with an ultrasound-based visual servoing system to enable fast tissue tracking. In vivo tests show RMS tracking errors of 0.77 mm for following the porcine mitral valve annulus trajectory. The results demonstrate that an ultrasound-guided robotic catheter system can accurately track the fast motion of the mitral valve.

Design considerations for an active soft orthotic system for shoulder rehabilitation

Strokes affect over 750,000 people annually in the United States. This significant and disabling condition can result in paralysis that must be treated by regular sessions with a dedicated physical therapist in order to regain motor function. However, the use of therapists is expensive, in high demand, and requires patient travel to a rehabilitation clinic. We propose an inexpensive and wearable upper body orthotics system that can be used at home to provide the same level of rehabilitation as the current physical therapy standard of care. The system is composed of a soft orthotic device with an integrated cable actuation system that is worn over the upper body, a limb position sensing system, and an actuator package. This paper presents initial design considerations and the evaluation of a proof of concept system for shoulder joint rehabilitation. Through simulations and experimental evaluation, the system is shown to be adjustable, easily wearable, and adaptable to misalignment and anatomical variations. Insights provided by these initial studies will inform the development of a complete upper body orthotic system.