Five degrees-of-freedom mechanical arm with remote center of motion (RCM) device for volumetric optical coherence tomography (OCT) retinal imaging.

Handheld optical coherence tomography (HH-OCT) is gaining popularity for diagnosing retinal diseases in neonates (e.g. retinopathy of prematurity). Diagnosis accuracy is degraded by hand tremor and patient motion when using commercially available handheld retinal OCT probes. This work presents a low-cost arm designed to address ergonomic challenges of holding a commercial OCT probe and alleviating hand tremor. Experiments with a phantom eye show enhanced geometric uniformity and volumetric accuracy when obtaining OCT scans with our device compared to handheld imaging approaches. An in-vivo porcine volumetric image was also obtained with the mechanical arm demonstrating clinical deployability.

Endovascular Detection of Catheter-Thrombus Contact by Vacuum Excitation.

OBJECTIVE: The objective of this work is to introduce and demonstrate the effectiveness of a novel sensing modality for contact detection between an off-the-shelf aspiration catheter and a thrombus. METHODS: A custom robotic actuator with a pressure sensor was used to generate an oscillatory vacuum excitation and sense the pressure inside the extracorporeal portion of the catheter. Vacuum pressure profiles and robotic motion data were used to train a support vector machine (SVM) classification model to detect contact between the aspiration catheter tip and a mock thrombus. Validation consisted of benchtop accuracy verification, as well as user study comparison to the current standard of angiographic presentation. RESULTS: Benchtop accuracy of the sensing modality was shown to be 99.67%. The user study demonstrated statistically significant improvement in identifying catheter-thrombus contact compared to the current standard. The odds ratio of successful detection of clot contact was 2.86 (p = 0.03) when using the proposed sensory method compared to without it. CONCLUSION: The results of this work indicate that the proposed sensing modality can offer intraoperative feedback to interventionalists that can improve their ability to detect contact between the distal tip of a catheter and a thrombus. SIGNIFICANCE: By offering a relatively low-cost technology that affords off-the-shelf aspiration catheters as clot-detecting sensors, interventionalists can improve the first-pass effect of the mechanical thrombectomy procedure while reducing procedural times and mental burden.

A Multi-Modal Sensor Array for Human-Robot Interaction and Confined Spaces Exploration Using Continuum Robots.

Safe human-robot interaction requires robots endowed with perception. This paper presents the design of a multi-modal sensory array for continuum robots, targeting operation in semi-structured confined spaces with human users. Active safety measures are enabled via sensory arrays capable of simultaneous sensing of proximity, contact, and force. Proximity sensing is achieved using time-of-flight sensors, while contact force is sensed using Hall effect sensors and embedded magnets. The paper presents the design and fabrication of these sensors, the communication protocol and multiplexing scheme used to allow an interactive rate of communication with a high-level controller, and an evaluation of these sensors for actively mapping the shape of the environment and compliance control using gestures and contact with the robot. Characterization of the proximity sensors is presented with considerations of sensitivity to lighting, color, and texture conditions. Also, characterization of the force sensing is presented. The results show that the multi-modal sensory array can enable pre and post-collision active safety measures and can also enable user interaction with the robot. We believe this new technology allows for increased safety for human-robot interaction in confined and semi-structures spaces due to its demonstrated capabilities of detecting impending collision and mapping the environment along the length of the robot. Future miniaturization of the electronics will also allow possible integration in smaller continuum and soft robots.

Continuum Robots for Medical Interventions.

Continuum robots are not constructed with discrete joints but, instead, change shape and position their tip by flexing along their entire length. Their narrow curvilinear shape makes them well suited to passing through body lumens, natural orifices, or small surgical incisions to perform minimally invasive procedures. Modeling and controlling these robots are, however, substantially more complex than traditional robots comprised of rigid links connected by discrete joints. Furthermore, there are many approaches to achieving robot flexure. Each presents its own design and modeling challenges, and to date, each has been pursued largely independently of the others. This article attempts to provide a unified summary of the state of the art of continuum robot architectures with respect to design for specific clinical applications. It also describes a unifying framework for modeling and controlling these systems while additionally explaining the elements unique to each architecture. The major research accomplishments are described for each topic and directions for the future progress needed to achieve widespread clinical use are identified.

A decade retrospective of medical robotics research from 2010 to 2020.

Robotics is a forward-looking discipline. Attention is focused on identifying the next grand challenges. In an applied field such as medical robotics, however, it is important to plan the future based on a clear understanding of what the research community has recently accomplished and where this work stands with respect to clinical needs and commercialization. This Review article identifies and analyzes the eight key research themes in medical robotics over the past decade. These thematic areas were identified using search criteria that identified the most highly cited papers of the decade. Our goal for this Review article is to provide an accessible way for readers to quickly appreciate some of the most exciting accomplishments in medical robotics over the past decade; for this reason, we have focused only on a small number of seminal papers in each thematic area. We hope that this article serves to foster an entrepreneurial spirit in researchers to reduce the widening gap between research and translation.

Investigation of Micro-motion Kinematics of Continuum Robots for Volumetric OCT and OCT-guided Visual Servoing.

Continuum robots (CR) have been recently shown capable of micron-scale motion resolutions. Such motions are achieved through equilibrium modulation using indirect actuation for altering either internal preload forces or changing the cross-sectional stiffness along the length of a continuum robot. Previously reported, but unexplained, turning point behavior is modeled using two approaches. An energy minimization approach is first used to explain the source of this behavior. Subsequently, a kinematic model using internal constraints in multi-backbone CRs is used to replicate this turning point behavior. An approach for modeling the micro-motion differential kinematics is presented using experimental data based on the solution of a system of linear matrix equations. This approach provides a closed-form approximation of the empirical micro-motion kinematics and could be easily used for real-time control. A motivating application of image-based biopsy using 3D optical coherence tomography (OCT) is envisioned and demonstrated in this paper. A system integration for generating OCT volumes by sweeping a custom B-mode OCT probe is presented. Results showing high accuracy in obtaining 3D OCT measurements are shown using a commercial OCT probe. Qualitative results using a miniature probe integrated within the robot are also shown. Finally, closed-loop visual servoing using OCT data is demonstrated for guiding a needle into an agar channel. Results of this paper present what we believe is the first embodiment of a continuum robot capable of micro and macro motion control for 3D OCT imaging. This approach can support the development of new technologies for CRs capable of surgical intervention and micro-motion for ultra-precision tasks.

A Review of Robotic and OCT-Aided Systems for Vitreoretinal Surgery.

The introduction of the intraocular vitrectomy instrument by Machemer et al. has led to remarkable advancements in vitreoretinal surgery enabling the limitations of human physiologic capabilities to be reached. To overcome the barriers of perception, tremor, and dexterity, robotic technologies have been investigated with current advancements nearing the feasibility for clinical use. There are four categories of robotic systems that have emerged through the research: (1) handheld instruments with intrinsic robotic assistance, (2) hand-on-hand robotic systems, (3) teleoperated robotic systems, and (4) magnetic guidance robots. This review covers the improvements and the remaining needs for safe, cost-effective clinical deployment of robotic systems in vitreoretinal surgery.

Modal-Based Kinematics and Contact Detection of Soft Robots.

Soft robots offer an alternative approach to manipulate within a constrained space while maintaining a safe interaction with the external environment. Owing to its adaptable compliance characteristic, external contact force can easily deform the robot shapes and lead to undesired robot kinematic and dynamic properties. Accurate contact detection and contact location estimation are of critical importance for soft robot modeling, control, trajectory planning, and eventually affect the success of task completion. In this article, we focus on the investigation of a one degree of freedom (1-DoF) soft pneumatic bending robot, which is regarded as one of the fundamental components to construct complex, multi-DoFs soft robots. This 1-DoF soft robot is modeled through the integral representation of the spatial curve, where direct and instantaneous kinematics are calculated explicitly through a modal method. The fixed centrode deviation method is used to detect the external contact and estimate the contact location. Simulation results and experimental studies indicate that the contact location can be accurately estimated by solving a nonlinear least-square optimization problem. Experimental validation shows that the proposed algorithm is able to successfully estimate the contact location with the estimation error of 1.46 mm.

Sensitivity Ellipsoids for Force Control of Magnetic Robots with Localization Uncertainty.

The navigation of magnetic medical robots typically relies on localizing an actuated, intracorporeal, ferromagnetic body and back-computing a necessary field and gradient that would result in a desired wrench on the device. Uncertainty in this localization degrades the precision of force transmission. Reducing applied force uncertainty may enhance tasks such as in-vivo navigation of miniature robots, actuation of magnetically guided catheters, tissue palpation, as well as simply ensuring a bound on forces applied on sensitive tissue. In this paper, we analyzed the effects of localization noise on force uncertainty by using sensitivity ellipsoids of the magnetic force Jacobian and introduced an algorithm for uncertainty reduction. We validated the algorithm in both a simulation study and in a physical experiment. In simulation, we observed reductions in estimated force uncertainty by factors of up to 2.8 and 3.1 when using one and two actuating magnets, respectively. On a physical platform, we demonstrated a force uncertainty reduction by a factor of up to 2.5 as measured using an external sensor. Being the first consideration of force uncertainty resulting from noisy localization, this work provides a strategy for investigators to minimize uncertainty in magnetic force transmission.

Sensorless Estimation of the Planar Distal Shape of a Tip-Actuated Endoscope.

Traditional endoscopes consist of a flexible body and a steerable tip with therapeutic capability. Although prior endoscopes have relied on operator pushing for actuation, recent robotic concepts have relied on the application of a tip force for guidance. In such case, the body of the endoscope can be passive and compliant; however, the body can have significant effect on mechanics of motion and may require modeling. As the endoscope body's shape is often unknown, we have developed an estimation method to recover the approximate distal shape, local to the endoscope's tip, where the tip position and orientation are the only sensed parameters in the system. We leverage a planar dynamic model and extended Kalman filter to obtain a constant-curvature shape estimate of a magnetically guided endoscope. We validated this estimator in both dynamic simulations and on a physical platform. We then used this estimate in a feed-forward control scheme and demonstrated improved trajectory following. This methodology can enable the use of inverse-dynamic control for the tip-based actuation of an endoscope, without the need for shape sensing.

Investigating variability in cochlear implant electrode array alignment and the potential of visualization guidance.

Background Internal cochlear anatomy is difficult to discern from external inspection, hindering cochlear implant electrode insertion. Methods A user study characterized the repeatability of standard surgical technique and examined the role of visual inspection and guidance cues in reducing electrode array insertion misalignment. Results Without guidance, a large spread in angles of insertion, up to 30°, was observed, highlighting the need for intraoperative guidance. Visual inspection did not significantly improve overall orientation, suggesting the need for alternate intracochlear visualization methods and/or increased training to effectively improve surgeon understanding of the visualized images. Visual cues and guidance software increased repeatability of surgeon performance, reducing one metric of repeatability to ±2°. Conclusions This study establishes a baseline for surgeon variability in cochlear implant insertion and supports the need and lays the groundwork for future intraoperative guidance techniques.

Dual-Continuum Design Approach for Intuitive and Low-Cost Upper Gastrointestinal Endoscopy.

OBJECTIVE: This paper introduces a methodology to design intuitive, low-cost, and portable devices for visual inspection of the upper gastrointestinal tract. METHODS: The proposed approach mechanically couples a multi-backbone continuum structure, as the user interface, and a parallel bellows actuator, as the endoscopic tip. Analytical modeling techniques derived from continuum robotics were adopted to describe the endoscopic tip motion from user input, accounting for variations in component size and pneumatic compressibility. The modeling framework was used to improve intuitiveness of user-to-task mapping. This was assessed against a 1:1 target, while ease-of-use was validated using landmark identification tasks performed in a stomach simulator by one expert and ten non-expert users; benchmarked against conventional flexible endoscopy. Pre-clinical validation consisted of comparative trials in in-vivo porcine and human cadaver models. RESULTS: Target mapping was achieved with an average error of 5° in bending angle. Simulated endoscopies were performed by an expert user successfully, within a time comparable to conventional endoscopy (<1 minute difference). Non-experts using the proposed device achieved visualization of the stomach in a shorter time (9s faster on average) than with a conventional endoscope. The estimated cost is <10 USD and <30 USD for disposable and reusable parts, respectively. Significance and Conclusions: Flexible endoscopes are complex and expensive devices, actuated via non-intuitive cable-driven mechanisms. They frequently break, requiring costly repair, and necessitate a dedicated reprocessing facility to prevent cross contamination. The proposed solution is portable, inexpensive, and easy to use, thus lending itself to disposable use by personnel without formal training in flexible endoscopy.

Preliminary Porcine In Vivo Evaluation of a Telerobotic System for Transurethral Bladder Tumor Resection and Surveillance.

INTRODUCTION: Transurethral resection of bladder tumors (TURBTs) can be a challenging procedure, primarily due to limitations in tooltip dexterity, visualization, and lack of tissue depth information. A transurethral robotic system was developed to revolutionize TURBTs by addressing some of these limitations. The results of three pilot in vivo porcine studies using the novel robotic system are presented and potential improvements are proposed based on experimental observations. MATERIALS AND METHODS: A transvesical endoscope with a mounted optically tracked camera was placed through the bladder of the swine under general anesthesia. Simulated bladder lesions were created by injecting HistoGel processing gel mixed with blue dye, transabdominally, into various locations in the bladder wall under endoscopic visualization. A 7-degree-of-freedom (DoF) robot was then used for transurethral resection/ablation of these simulated tumors. An independent 2-DoF distal laser arm (DLA) was deployed through the robot for laser ablation and was assisted by a manually controlled gripper for en bloc resection attempts. RESULTS: Lesions were created and ablated using our novel endoscopic robot in the swine bladder. Full accessibility of the bladder, including the bladder neck and dome, was demonstrated without requiring bladder deflation or pubic compression. Simulated lesions were ablated using the holmium laser. En bloc resection was demonstrated using the DLA and a manual grasper. CONCLUSION: Feasibility of robot-assisted en bloc resection was demonstrated. Main challenges were lack of depth perception and visual occlusion induced by the transvesical endoscope. Recommendations are given to enhance robot-assisted TURBTs. Lessons learned through these pilot swine studies verify the feasibility of robot-assisted TURBTs while informing designers about critical aspects needed for future clinical deployment.

Detection of modiolar proximity through bipolar impedance measurements.

OBJECTIVES: To test the hypothesis that bipolar electrical impedance measurements in perimodiolar cochlear implants (CIs) may be used to differentiate between perimodiolar insertion technique favoring proximity to the modiolus or lateral wall. STUDY DESIGN AND METHODS: Bipolar impedances are a measure of electrical resistance between pairs of electrode contacts in a CI. Stimulation is through biphasic pulses at fixed frequency. Impedance measurements were made in real time through sequential sampling of electrode pairs. Perimodiolar electrodes were inserted in temporal bones using one of two techniques: 1) In the standard insertion technique (SIT), the electrode array slides along the lateral wall during insertion. 2) In the Advance Off Stylet (Cochlear Ltd. Sydney) technique (AOS), the electrode maintains modiolar contact throughout the insertion process. A set of 22 insertions were performed in temporal bone specimens using perimodiolar electrode arrays with both AOS and SIT. Buffered saline was used as a substitute for natural perilymph based on similar electrical conductivity properties. Impedance with and without stylet removal were recorded with a 30-second sampling window at final insertion depth. RESULTS: There is a significant difference in bipolar impedance measures between AOS and SIT, with impedances rising in measurements with stylet removal. Evaluation was based on two-sided analysis of variance considering technique and electrode with P < 0.025. CONCLUSION: Bipolar electrical impedance can be used to detect relative motion toward the modiolus inside the cochlea. This detection method has the potential to optimize intraoperative placement of perimodiolar electrode arrays during implantation. We anticipate that this will result in lower excitation thresholds and improved hearing outcome. LEVEL OF EVIDENCE: NA. Laryngoscope, 127:1413-1419, 2017.

Kinematic and experimental investigation of manual resection tools for transurethral bladder tumor resection.

BACKGROUND: Transurethral Resection of Bladder Tumors (TURBT) is a challenging procedure partly due to resectoscope limitations. To date, manual resection performance has not been fully characterized. This work characterizes manual resection performance in the bladder while analyzing the effect of resection location on accuracy. METHODS: Kinematic simulations are used to assess kinematic measures of resection dexterity. An experimental protocol for manual resection accuracy assessment is developed. Cross correlations between the theoretical performance measures and the observed experimental accuracy are investigated. RESULTS: Tangential accuracy correlates relatively strongly with normal singular value and moderately with tangential kinematic conditioning index and tangential minimum singular value. Simulations also clarified difficulties in resecting close to the bladder neck. CONCLUSIONS: Measures to evaluate accuracy and dexterity of TURBT from a kinematic viewpoint are presented to provide a currently missing quantified dexterity baseline in manual TURBT. Limitations in various bladder regions are illustrated. Copyright © 2016 John Wiley & Sons, Ltd.

Steerable Robot-assisted Micromanipulation in the Middle Ear: Preliminary Feasibility Evaluation.

HYPOTHESIS: The use of a robotic manipulator with a dexterously orientable gripper will expand the ability of middle ear surgeons to perform precise tasks and access otherwise challenging anatomic regions. BACKGROUND: Middle ear surgery presents unique challenges because of the constrained operative space and limited access to certain anatomic regions. METHODS: A custom-designed robot with a sideways-reaching gripper was used to evaluate feasibility of manipulation tasks in different middle-ear anatomical zones. Reachable workspace within the middle ear, accuracy of free-space path following, and tool steadiness were compared between robotic telemanipulation and manual control. Preliminarily assessments of the robot's clinical utility included: 1) touching the round window niche, Eustachian tube orifice, and sinus tympani; 2) placing a stapes prosthesis; 3) removal of mockup diseased tissue in the sinus tympani. RESULTS: The reachable workspace in the middle ear was considerably greater with the robot as compared with manual manipulation using a Rosen needle. In a simple path-tracing task outside the ear, robotic telemanipulation was associated with significantly reduced error. Within the middle ear, the robot contributed to steadier movement, but longer task completion time. The gripper successfully placed a 4.5 mm piston prosthesis, accessed the round window niche, Eustachian tube orifice, and removed mockup disease from the sinus tympani. CONCLUSION: This study demonstrates that robotic assistance using steerable tools allows surgeons to access challenging anatomic regions of the middle ear. Coordinated and accurate manipulation is evidenced by motion analyses and completion of feasibility tasks within the middle ear.

Jacobian-Based Iterative Method for Magnetic Localization in Robotic Capsule Endoscopy.

The purpose of this study is to validate a Jacobian-based iterative method for real-time localization of magnetically controlled endoscopic capsules. The proposed approach applies finite-element solutions to the magnetic field problem and least-squares interpolations to obtain closed-form and fast estimates of the magnetic field. By defining a closed-form expression for the Jacobian of the magnetic field relative to changes in the capsule pose, we are able to obtain an iterative localization at a faster computational time when compared with prior works, without suffering from the inaccuracies stemming from dipole assumptions. This new algorithm can be used in conjunction with an absolute localization technique that provides initialization values at a slower refresh rate. The proposed approach was assessed via simulation and experimental trials, adopting a wireless capsule equipped with a permanent magnet, six magnetic field sensors, and an inertial measurement unit. The overall refresh rate, including sensor data acquisition and wireless communication was 7 ms, thus enabling closed-loop control strategies for magnetic manipulation running faster than 100 Hz. The average localization error, expressed in cylindrical coordinates was below 7 mm in both the radial and axial components and 5° in the azimuthal component. The average error for the capsule orientation angles, obtained by fusing gyroscope and inclinometer measurements, was below 5°.

Evaluation of microsurgical tasks with OCT-guided and/or robot-assisted ophthalmic forceps.

Real-time intraocular optical coherence tomography (OCT) visualization of tissues with surgical feedback can enhance retinal surgery. An intraocular 23-gauge B-mode forward-imaging co-planar OCT-forceps, coupling connectors and algorithms were developed to form a unique ophthalmic surgical robotic system. Approach to the surface of a phantom or goat retina by a manual or robotic-controlled forceps, with and without real-time OCT guidance, was performed. Efficiency of lifting phantom membranes was examined. Placing the co-planar OCT imaging probe internal to the surgical tool reduced instrument shadowing and permitted constant tracking. Robotic assistance together with real-time OCT feedback improved depth perception accuracy. The first-generation integrated OCT-forceps was capable of peeling membrane phantoms despite smooth tips.

Robot-assisted transnasal laryngoplasty in cadaveric models: Quantifying forces and identifying challenges.

OBJECTIVES/HYPOTHESIS: We expanded our prior work with transnasal robotic surgery (TNRS) in this study with the following aims: 1) use a cadaveric model to evaluate the feasibility of laryngoplasty with TNRS, 2) measure robot insertion times and forces, and 3) identify operational challenges to further guide the development of a flexible robotic system. STUDY DESIGN: Cadaveric study. METHODS: A 5-mm robot was guided to the larynx via a transnasal approach. Insertion times and forces using TNRS and a 4-mm flexible fiberoptic laryngoscope (FFL) were measured. Target sites on the true vocal cords were marked, and the TNRS was telemanipulated to perform injection laryngoplasty. RESULTS: Insertion times averaged 5.05 seconds (range, 3.8-10.4 seconds) for the TNRS and 7.97 seconds (range, 6.2-11.6 seconds) for the FFL. Insertion forces averaged 2.06 newtons (range, 1.56-5.55 newtons) for the TNRS and 0.43 newtons (range, 0.157-1.138 newtons) for the FFL. The unpaired t test between times and forces revealed P values of .0024 and .0000658, respectively. Seven target injection sites on three vocal cords in two cadaveric larynxes were successfully injected. In two out of nine sites marked, we were unable to access the vocal cord due tongue base collapse that obscured the posterior airway. CONCLUSIONS: TNRS is able to effectively access the larynx, although in a supine model may be limited by tongue base collapse. Forces with TNRS were significantly higher than with the FFL, albeit within the same scale. Despite increased forces, there was no evidence of tissue trauma using TNRS. LEVEL OF EVIDENCE: NA Laryngoscope, 125:1166-1168, 2015.

A pilot ex vivo evaluation of a telerobotic system for transurethral intervention and surveillance.

INTRODUCTION: Transurethral resection of bladder tumor (TURBT) and pathological staging are both standard surgical therapies for nonmuscle-invasive bladder cancer and integral parts of the diagnostic evaluation and progression monitoring of all bladder tumors. We developed and tested a dexterous robot that can fit through a standard resectoscope for evaluation for possible en bloc resection of bladder tumors, especially tumors along the dome and anterior wall of the bladder. MATERIALS AND METHODS: Our dexterous robot uses a continuum (snake-like) mechanical architecture with three working channels through which a fiberscope, biopsy graspers, and a holmium laser were placed. The continuum robot has two segments. Using indigo carmine, injections were performed through the detrusor muscle into the mucosa of the ex vivo bovine bladders at a total of 11 positions throughout all quadrants of the bladder. The snake robot was used in conjunction with the holmium laser to ablate nine of the lesions; two additional lesions were resected en bloc using the grasper and the laser down through the muscle layer. RESULTS: Both experiments showed that the robotic system was able to directly visualize all 11 targets. In both the bladders, we were able to resect en bloc two tumors using the grasper and 200 µm holmium laser fiber down to the muscle layer indicating a good resection. All of the other targets were completely ablated using the holmium laser. CONCLUSION: The dexterous robot allowed for visualization as well as provided adequate ablation and en bloc resection of bladder lesions throughout the entire bladder.