Corrections to "Micropositioning and Control of an Underactuated Platform for Microscopic Applications".

[This corrects the article PMC5110010.].

Preclinical Evaluation of a Novel Steerable Robotic Neuroendoscope Tool.

BACKGROUND AND OBJECTIVES: To improve the outcomes of minimally invasive, endoscopic, intracranial procedures, steerable robotic tools have been developed but still require thorough evaluation before use in a clinical setting. This paper compares a novel steerable robotic neuroendoscope tool against a standard rigid tool. METHODS: Seventeen participants, 8 nonmedical and 9 medical (neurosurgery residents and fellows), were recruited. The evaluation trial consisted of a task that was completed using either a rigid tool or the steerable tool, followed by the completion of a qualitative survey. Target reach time and tool movement volume (TMV) were recorded for each trial and analyzed. The tools were evaluated within a realistic phantom model of the brain. RESULTS: Preclinical evaluation of both tools showed that average target reach time for the steerable tool among medical personnel (15.0 seconds) was longer than that of the rigid tool (5.9 seconds). However, the average TMV for the steerable tool (0.178 cm 3 ) was much lower than that of the rigid tool (0.501 cm 3 ) for medical personnel, decreasing the TMV by 64.47%. CONCLUSION: The steerable tool required more training and practice in comparison with the standard rigid tool, but it decreased the overall endoscope movement volume, which is a source of parenchymal injury associated with endoscopic procedures.

Compact Design and Task Space Control of a Robotic Transcatheter Delivery System for Mitral Valve Implant.

Mitral regurgitation (MR) is one of the most common valvular abnormalities, and the gold-standard for treatment is surgical mitral valve repair/replacement. Most patients with severe MR are over the age of 75, which makes open-heart surgery challenging. Thus, minimally invasive surgeries using transcatheter approaches are gaining popularity. This paper proposes the next generation of a robotic transcatheter delivery system for the mitral valve implant that focuses on the design of the actuation system, modeling, and task space control. The proposed actuation system is compact while still enabling bidirectional torsion, bending, and prismatic joint motion. A pulley structure is employed to actuate the torsion and bending joints using only one motor per joint in conjunction with an antagonistic passive spring to reduce tendon slack. The robotic transcatheter is also optimized to increase its stability and reduce bending deflection. An inverse kinematics model (with an optimization algorithm), singularity analysis method, and joint hysteresis and compensation model are developed and verified. Finally, a task space controller is also proposed. Experiments, including trajectory tracking and demonstrations of the robot motion in an ex vivo porcine heart and a phantom heart through a tortuous path are presented.

Telerobotic Transcatheter Delivery System for Mitral Valve Implant.

Mitral regurgitation (MR) is the most common type of valvular heart disease, affecting over 2% of the world population, and the gold-standard treatment is surgical mitral valve repair/replacement. Compared to open-heart surgeries, minimally invasive surgeries (MIS) using transcatheter approaches have become popular because of their notable benefits such as less postoperative pain, shorter hospital stay, and faster recovery time. However, commercially available catheters are manually actuated, causing over-exposure of clinical staff to radiation and increased risk of human error during medical interventions. To tackle this problem, in this letter, we propose a telerobotic transcatheter delivery system, which consists of a robotic catheter (5.7 mm OD), a reinforced guide tube (1.11m length), and an actuation system. We present the robotic system design, fabrication of key components, and static model of reinforced quadlumen tube. The robot interface design enables the user to intuitively control the robot. We demonstrate the effectiveness of the telerobotic transcatheter delivery system and reinforced quadlumen tube in a realistic human cardiovascular phantom for preclinical evaluation.

Model-based Design of the COAST Guidewire Robot for Large Deflection.

Minimally invasive endovascular procedures involve the manual placement of a guidewire, which is made difficult by vascular tortuosity and the lack of precise tip control. Steerable guidewire systems have been developed with tendon-driven, magnetic, and concentric tube actuation strategies to enable precise tip control, however, selecting machining parameters for such robots does not have a strict procedure. In this paper, we develop a systematic design procedure for selecting the tube pairs of the COaxially Aligned STeerable (COAST) guidewire robot. This includes the introduction of a mechanical model that accounts for micromachining-induced pre-curvatures with the goal of determining design parameters that reduce combined distal tip pre-curvature and minimize abrupt changes in actuated tip position for the COAST guidewire robot through selection of the best flexural rigidity between the tube pairs. We present adjustments in the kinematics modeling of COAST robot tip bending motion, and use these to characterize the bending behavior of the COAST robot for varying geometries of the micromachined tubes, with an average RMSE value for the tip position error of 0.816 mm in the validation study.

Towards comprehensive evaluation of the FLEXotendon glove-III: a case series evaluation in pediatric clinical cases and able-bodied adults.

Injuries involving the nervous system, such as a brachial plexus palsy or traumatic brain injury, can lead to impairment in the functionality of the hand. Assistive robotics have been proposed as a possible method to improve patient outcomes in rehabilitation. The work presented here evaluates the FLEXotendon Glove-III, a 5 degree-of-freedom, voice-controlled, tendon-driven soft robotic hand exoskeleton, with two human subjects with hand impairments and four able-bodied subjects. The FLEXotendon Glove-III was evaluated on four unimpaired subjects, in conjunction with EMG sensor data, to determine the quantitative performance of the glove in applied pinch force, perturbation resistance, and exertion reduction. The exoskeleton system was also evaluated on two subjects with hand impairments, using two standardized hand function tests, the Jebsen-Taylor Hand Function Test and the Toronto Rehabilitation Institute Hand Function Test. The subjects were also presented with three qualitative questionnaires, the Capabilities of Upper Extremities Questionnaire, the Quebec User Evaluation of Satisfaction with Assistive Technology, and the Orthotics Prosthetics User Survey-Satisfaction module. From the previous design, minor design changes were made to the exoskeleton. The quick connect system was redesigned for improved performance, the number of motors was reduced to decrease overall footprint, and the entire system was placed into a compact acrylic case that can be placed into a backpack for increased portability.

Evaluation of the FLEXotendon glove-III through a human subject case study.

Cervical spinal cord injury (SCI) can significantly impair an individual's hand functionality due to the disruption of nerve signals from the brain to the upper extremity. Robotic assistive hand exoskeletons have been proposed as a potential technology to facilitate improved patient rehabilitation outcomes, but few exoskeleton studies utilize standardized hand function tests and questionnaires to produce quantitative data regarding exoskeleton performance. This work presents the human subject case study evaluation of the FLEXotendon Glove-III, a 5 degree-of-freedom voice-controlled, tendon-driven soft robotic assistive hand exoskeleton for individuals with SCI. The exoskeleton system was evaluated in a case study with two individuals with SCI through two standardized hand function tests namely, the Jebsen-Taylor Hand Function Test and the Toronto Rehabilitation Institute Hand Function Test and three questionnaires (Capabilities of Upper Extremities Questionnaire, Orthotics Prosthetics Users Survey, Quebec User Evaluation of Satisfaction with Assistive Technology). Minor design changes were made to the exoskeleton: integrated fingertip force sensors to sense excessive grasp force, a quick connect system to expedite the exoskeleton glove swapping process between users, compact tendon tension sensors to measure tendon force for admittance control, and a redesigned smartphone app to encompass all aspects of exoskeleton use.

Supervised segmentation for guiding peripheral revascularization with forward-viewing, robotically steered ultrasound guidewire.

BACKGROUND: Approximately 500 000 patients present with critical limb ischemia (CLI) each year in the U.S., requiring revascularization to avoid amputation. While peripheral arteries can be revascularized via minimally invasive procedures, 25% of cases with chronic total occlusions are unsuccessful due to inability to route the guidewire beyond the proximal occlusion. Improvements to guidewire navigation would lead to limb salvage in a greater number of patients. PURPOSE: Integrating ultrasound imaging into the guidewire could enable direct visualization of routes for guidewire advancement. In order to navigate a robotically-steerable guidewire with integrated imaging beyond a chronic occlusion proximal to the symptomatic lesion for revascularization, acquired ultrasound images must be segmented to visualize the path for guidewire advancement. METHODS: The first approach for automated segmentation of viable paths through occlusions in peripheral arteries is demonstrated in simulations and experimentally-acquired data with a forward-viewing, robotically-steered guidewire imaging system. B-mode ultrasound images formed via synthetic aperture focusing (SAF) were segmented using a supervised approach (U-net architecture). A total of 2500 simulated images were used to train the classifier to distinguish the vessel wall and occlusion from viable paths for guidewire advancement. First, the size of the synthetic aperture resulting in the highest classification performance was determined in simulations (90 test images) and compared with traditional classifiers (global thresholding, local adaptive thresholding, and hierarchical classification). Next, classification performance as a function of the diameter of the remaining lumen (0.5 to 1.5 mm) in the partially-occluded artery was tested using both simulated (60 test images at each of 7 diameters) and experimental data sets. Experimental test data sets were acquired in four 3D-printed phantoms from human anatomy and six ex vivo porcine arteries. Accuracy of classifying the path through the artery was evaluated using microcomputed tomography of phantoms and ex vivo arteries as a ground truth for comparison. RESULTS: An aperture size of 3.8 mm resulted in the best-performing classification based on sensitivity and Jaccard index, with a significant increase in Jaccard index (p < 0.05) as aperture diameter increased. In comparing the performance of the supervised classifier and traditional classification strategies with simulated test data, sensitivity and F1 score for U-net were 0.95 ± 0.02 and 0.96 ± 0.01, respectively, compared to 0.83 ± 0.03 and 0.41 ± 0.13 for the best-performing conventional approach, hierarchical classification. In simulated test images, sensitivity (p < 0.05) and Jaccard index both increased with increasing artery diameter (p < 0.05). Classification of images acquired in artery phantoms with remaining lumen diameters ≥ 0.75 mm resulted in accuracies > 90%, while mean accuracy decreased to 82% when artery diameter decreased to 0.5 mm. For testing in ex vivo arteries, average binary accuracy, F1 score, Jaccard index, and sensitivity each exceeded 0.9. CONCLUSIONS: Segmentation of ultrasound images of partially-occluded peripheral arteries acquired with a forward-viewing, robotically-steered guidewire system was demonstrated for the first-time using representation learning. This could represent a fast, accurate approach for guiding peripheral revascularization.

Real-time Pose Tracking for a Continuum Guidewire Robot under Fluoroscopic Imaging.

Atherosclerosis is a medical condition that causes buildup of plaque in the blood vessels and narrowing of the arteries. Surgeons often treat this condition through angioplasty with catheter placements. Continuum guidewire robots offer significant advantages for catheter placements due to their dexterity. Tracking these guidewire robots and their surrounding workspace under fluoroscopy in real-time can be useful for visualization and accurate control. This paper discusses algorithms and methods to track the shape and orientation of the guidewire and the surrounding workspaces of phantom vasculatures in real-time under C-arm fluoroscopy. The shape of continuum guidewires is found through a semantic segmentation architecture based on MobileNetv2 with a Tversky loss function to deal with class imbalances. This shape is refined through medial axis filtering and parametric curve fitting to quantitatively describe the guidewire's pose. Using a constant curvature assumption for the guidewire's bending segments, the parameters that describe the joint variables are estimated in real-time for a tendon-actuated COaxially Aligned STeerable (COAST) guidewire robot and tracked through its traversal of an aortic bifurcation phantom. The accuracy of the tracking is ~90% and the execution times are within 100ms, and hence this method is deemed suitable for real-time tracking.

Design and Modeling of a Sub-2 mm Steerable Neuroendoscopic Grasping Tool.

Minimally invasive procedures, such as endoscopic third ventriculostomy (ETV), benefit from the increased dexterity and safety that surgical continuum robots can bring. However, due to their natural compliance, new compatible end-effectors, such as graspers or scissors, must be developed and their actuation must be considered when developing the robotic structures in which they are housed due to the inherent coupling that will be introduced. In this paper, we integrate a tendon-driven meso-scale grasper, with a closed configuration diameter of 1.69 mm, into a 2 degree-of-freedom (DoF) tendon-driven neurosurgical robot with an outer diameter of less than 2 mm. Furthermore, the kinematics of the grasper is validated and an analysis of the coupling between the grasper and the robotic joints is conducted in order to evaluate the design performance.

Simultaneous Shape and Tip Force Sensing for the COAST Guidewire Robot.

Placement of catheters in minimally invasive cardiovascular procedures is preceded by navigating to the target lesion with a guidewire. Traversing through tortuous vascular pathways can be challenging without precise tip control, potentially resulting in the damage or perforation of blood vessels. To improve guidewire navigation, this paper presents 3D shape reconstruction and tip force sensing for the COaxially Aligned STeerable (COAST) guidewire robot using a triplet of adhered single core fiber Bragg grating sensors routed centrally through the robot's slender structure. Additionally, several shape reconstruction algorithms are compared, and shape measurements are utilized to enable tip force sensing. Demonstration of the capabilities of the robot is shown in free air where the shape of the robot is reconstructed with average errors less than 2mm at the guidewire tip, and the magnitudes of forces applied to the tip are estimated with an RMSE of 0.027N or less.

Fluoroscopic Image-Based 3-D Environment Reconstruction and Automated Path Planning for a Robotically Steerable Guidewire.

Cardiovascular diseases are the leading cause of death globally and surgical treatments for these often begin with the manual placement of a long compliant wire, called a guidewire, through different vasculature. To improve procedure outcomes and reduce radiation exposure, we propose steps towards a fully automated approach for steerable guidewire navigation within vessels. In this paper, we utilize fluoroscopic images to fully reconstruct 3-D printed phantom vasculature models by using a shape-from-silhouette algorithm. The reconstruction is subsequently de-noised using a deep learning-based encoder-decoder network and morphological filtering. This volume is used to model the environment for guidewire traversal. Following this, we present a novel method to plan an optimal path for guidewire traversal in three-dimensional vascular models through the use of slice planes and a modified hybrid A-star algorithm. Finally, the developed reconstruction and planning approaches are applied to an ex vivo porcine aorta, and navigation is demonstrated through the use of a tendon-actuated COaxially Aligned STeerable guidewire (COAST).

State of the Art and Future Opportunities in MRI-Guided Robot-Assisted Surgery and Interventions.

Magnetic resonance imaging (MRI) can provide high-quality 3-D visualization of target anatomy, surrounding tissue, and instrumentation, but there are significant challenges in harnessing it for effectively guiding interventional procedures. Challenges include the strong static magnetic field, rapidly switching magnetic field gradients, high-power radio frequency pulses, sensitivity to electrical noise, and constrained space to operate within the bore of the scanner. MRI has a number of advantages over other medical imaging modalities, including no ionizing radiation, excellent soft-tissue contrast that allows for visualization of tumors and other features that are not readily visible by other modalities, true 3-D imaging capabilities, including the ability to image arbitrary scan plane geometry or perform volumetric imaging, and capability for multimodality sensing, including diffusion, dynamic contrast, blood flow, blood oxygenation, temperature, and tracking of biomarkers. The use of robotic assistants within the MRI bore, alongside the patient during imaging, enables intraoperative MR imaging (iMRI) to guide a surgical intervention in a closed-loop fashion that can include tracking of tissue deformation and target motion, localization of instrumentation, and monitoring of therapy delivery. With the ever-expanding clinical use of MRI, MRI-compatible robotic systems have been heralded as a new approach to assist interventional procedures to allow physicians to treat patients more accurately and effectively. Deploying robotic systems inside the bore synergizes the visual capability of MRI and the manipulation capability of robotic assistance, resulting in a closed-loop surgery architecture. This article details the challenges and history of robotic systems intended to operate in an MRI environment and outlines promising clinical applications and associated state-of-the-art MRI-compatible robotic systems and technology for making this possible.

Dual-Resonance (16/32 MHz) Piezoelectric Transducer With a Single Electrical Connection for Forward-Viewing Robotic Guidewire.

Peripheral artery disease (PAD) affects more than 200 million people globally. Minimally invasive endovascular procedures can provide relief and salvage limbs while reducing injury rates and recovery times. Unfortunately, when a calcified chronic total occlusion is encountered, ~25% of endovascular procedures fail due to the inability to advance a guidewire using the view provided by fluoroscopy. To enable a sub-millimeter, robotically steerable guidewire to cross these occlusions, a novel single-element, dual-band transducer is developed that provides simultaneous multifrequency, forward-viewing imaging with high penetration depth and high spatial resolution while requiring only a single electrical connection. The design, fabrication, and acoustic characterization of this device are described, and proof-of-concept imaging is demonstrated in an ex vivo porcine artery after integration with a robotically steered guidewire. Measured center frequencies of the developed transducer were 16 and 32 MHz, with -6 dB fractional bandwidths of 73% and 23%, respectively. When imaging a 0.2-mm wire target at a depth of 5 mm, measured -6 dB target widths were 0.498 ± 0.02 and 0.268 ± 0.01 mm for images formed at 16 and 32 MHz, respectively. Measured SNR values were 33.3 and 21.3 dB, respectively. The 3-D images of the ex vivo artery demonstrate high penetration for visualizing vessel morphology at 16 MHz and ability to resolve small features close to the transducer at 32 MHz. Using images acquired simultaneously at both frequencies as part of an integrated forward-viewing, guidewire-based imaging system, an interventionalist could visualize the best path for advancing the guidewire to improve outcomes for patients with PAD.

Towards the Design and Development of a Robotic Transcatheter Delivery System for Mitral Valve Implant.

Minimally-invasive surgeries using transcatheter approaches and sophisticated imaging modalities are gaining popularity to treat mitral regurgitation (MR). This paper proposes the next generation of a robotic catheter to deliver an implant onto the mitral valve (MV) through a transseptal approach. The proposed robot has an outer diameter (OD) of 5.7 mm, a rigid distal end length of 20 mm, a prismatic tube that can be advanced by 50-60 mm, and a bending joint that can easily bend 120° to reach the valve opening. The implant can be rotated 75° bidirectionally by the distal torsion joint to orient it with the MV leaflet for precise implantation. The robotic joints are modeled individually, the forward and inverse kinematics are derived, and the robot motion validation is carried out through experimentation. A modified kinematics (MK) model, Prandtl-Ishlinskii (PI) hysteresis model, and hybrid of MK and PI model are used to compensate for the catheter nonlinearities. A preliminary study is conducted to evaluate if force sensing can be used to compensate for the effects of fluid flow. Also, the implantation procedure is demonstrated in a phantom heart.

Kinematic Modeling and Jacobian-based Control of the COAST Guidewire Robot.

Manual guidewire navigation and placement for minimally invasive surgeries suffer from technical challenges due to imprecise tip motion control to traverse highly tortuous vasculature. Robotically steerable guidewires can address these challenges by actuating a compliant tip through multiple degrees-of-freedom for maneuvering through vascular pathways. In this paper, we detail the kinematic mapping of a COaxially Aligned STeerable (COAST) guidewire robot that is capable of executing follow-the-leader motion in three dimensional vascular pathways. We also develop an analytical Jacobian model to perform velocity kinematics for the robot and finally, we implement Jacobian-based control to demonstrate follow-the-leader motion of the guidewire in free space, within 3D-printed phantoms, and within ex vivo animal vasculature.

Towards Real-time pose estimation of the Mitral Valve Robot under C-arm X-ray Fluoroscopy.

Mitral regurgitation (MR) is a condition caused by a deformity in the mitral valve leading to the backflow of blood into the left atrium. MR can be treated through a minimally invasive procedure and our lab is currently developing a robot that could potentially be used to treat MR. The robot would carry a clip that latches onto the valve's leaflets and closes them to minimize leakage. The robot's accurate localization is needed to navigate the clip to the leaflets successfully. This paper discusses algorithms used to track the clip's position and orientation under real-time using C-arm fluoroscopy. The positions are found through a deep learning semantic segmentation framework and the pose is found by calculating its bending and rotational angles. The robot's bending angle and the clip's rotational angle is found through an equivalent ellipse algorithm and an SVM classifier, respectively, and were validated by comparing orientations obtained from an electromagnetic tracker. The bending angle calculation has an average error of 7.7° and the rotational angle calculation is 76% for classifying them into five classes. Execution times are within 100ms and hence this could be a promising approach in real-time pose estimation.

A Robotically Steerable Guidewire With Forward-Viewing Ultrasound: Development of Technology for Minimally-Invasive Imaging.

OBJECTIVE: The current standard of care for peripheral chronic total occlusions involves the manual routing of a guidewire under fluoroscopy. Despite significant improvements in recent decades, navigation remains clinically challenging with high rates of procedural failure and iatrogenic injury. To address this challenge, we present a proof-of-concept robotic guidewire system with forward-viewing ultrasound imaging to allow visualization and maneuverability through complex vasculature. METHODS: A 0.035" guidewire-specific ultrasound transducer with matching layer and acoustic backing was designed, fabricated, and characterized. The effect of guidewire motion on signal decorrelation was assessed with simulations and experimentally, driving the development of a synthetic aperture beamforming approach to form images as the transducer is steered on the robotic guidewire. System performance was evaluated by imaging wire targets in water. Finally, proof-of-concept was demonstrated by imaging an ex vivo artery. RESULTS: The designed custom transducer was fabricated with a center frequency of 15.7 MHz, 45.4% fractional bandwidth, and 31 dB SNR. In imaging 20 µm wire targets at a depth of 6 mm, the lateral -6 dB target width was 0.25 ± 0.03 mm. The 3D artery reconstruction allowed visualization of vessel wall structure and lumen. CONCLUSION: Initial proof-of-concept for an ultrasound transducer-tipped steerable guidewire including 3D image formation without an additional sensor to determine guidewire position was demonstrated for a sub-mm system with an integrated ultrasound transducer and a robotically-steered guidewire. SIGNIFICANCE: The developed forward-viewing, robotically-steered guidewire may enable navigation through occluded vascular regions that cannot be crossed with current methods.

Image Guided Mitral Valve Replacement: Registration of 3D Ultrasound and 2D X-ray Images.

Mitral valve repair or replacement is important in the treatment of mitral regurgitation. For valve replacement, a transcatheter approach had the possibility of decrease the invasiveness of the procedure while retaining the benefit of replacement over repair. However, fluoroscopy images acquired during the procedure provide no anatomical information regarding the placement of the probe tip once the catheter has entered a cardiac chamber. By using 3D ultrasound and registering the 3D ultrasound images to the fluoroscopy images, a physician can gain a greater understanding of the mitral valve region during transcatheter mitral valve replacement surgery. In this work, we present a graphical user interface which allows the registration of two co-planar X-ray images with 3D ultrasound during mitral valve replacement surgery.

Towards FBG-Based Shape Sensing for Micro-scale and Meso-Scale Continuum Robots with Large Deflection.

Endovascular and endoscopic surgical procedures require micro-scale and meso-scale continuum robotic tools to navigate complex anatomical structures. In numerous studies, fiber Bragg grating (FBG) based shape sensing has been used for measuring the deflection of continuum robots on larger scales, but has proved to be a challenge for micro-scale and meso-scale robots with large deflections. In this paper, we have developed a sensor by mounting an FBG fiber within a micromachined nitinol tube whose neutral axis is shifted to one side due to the machining. This shifting of the neutral axis allows the FBG core to experience compressive strain when the tube bends. The fabrication method of the sensor has been explicitly detailed and the sensor has been tested with two tendon-driven micro-scale and meso-scale continuum robots with outer diameters of 0.41 mm and 1.93 mm respectively. The compact sensor allows repeatable and reliable estimates of the shape of both scales of robots with minimal hysteresis. We propose an analytical model to derive the curvature of the robot joints from FBG fiber strain and a static model that relates joint curvature to the tendon force. Finally, as proof-of-concept, we demonstrate the feasibility of our sensor assembly by combining tendon force feedback and the FBG strain feedback to generate reliable estimates of joint angles for the meso-scale robot.