Exceeding traditional curvature limits of concentric tube robots through redundancy resolution.

Understanding elastic instability has been a recent focus of concentric tube robot research. Modeling advances have enabled prediction of when instabilities will occur and produced metrics for the stability of the robot during use. In this paper, we show how these metrics can be used to resolve redundancy to avoid elastic instability, opening the door for the practical use of higher curvature designs than have previously been possible. We demonstrate the effectiveness of the approach using a three-tube robot that is stabilized by redundancy resolution when following trajectories that would otherwise result in elastic instabilities. We also show that it is stabilized when teleoperated in ways that otherwise produce elastic instabilities. Lastly, we show that the redundancy resolution framework presented here can be applied to other control objectives useful for surgical robots, such as maximizing or minimizing compliance in desired directions.

Towards inferring positioning of straight cochlear-implant electrode arrays during insertion using real-time impedance sensing.

BACKGROUND: Cochlear-implant electrode arrays (EAs) are currently inserted with limited feedback, and impedance sensing has recently shown promise for EA localisation. METHODS: We investigate the use of impedance sensing to infer the progression of an EA during insertion. RESULTS: We show that the access resistance component of bipolar impedance sensing can detect when a straight EA reaches key anatomical locations in a plastic cochlea and when each electrode contact enters/exits the cochlea. We also demonstrate that dual-sided electrode contacts can provide useful proximity information and show the real-time relationship between impedance and wall proximity in a cadaveric cochlea for the first time. CONCLUSION: The access resistance component of bipolar impedance sensing has high potential for estimating positioning information of EAs relative to anatomy during insertion. Main limitations of this work include using saline as a surrogate for human perilymph in ex vivo models and using only one type of EA.

A Safe Framework for Quantitative In Vivo Human Evaluation of Image Guidance.

Goal: We present a new framework for in vivo image guidance evaluation and provide a case study on robotic partial nephrectomy. Methods: This framework (called the "bystander protocol") involves two surgeons, one who solely performs the therapeutic process without image guidance, and another who solely periodically collects data to evaluate image guidance. This isolates the evaluation from the therapy, so that in-development image guidance systems can be tested without risk of negatively impacting the standard of care. We provide a case study applying this protocol in clinical cases during robotic partial nephrectomy surgery. Results: The bystander protocol was performed successfully in 6 patient cases. We find average lesion centroid localization error with our IGS system to be 6.5 mm in vivo compared to our prior result of 3.0 mm in phantoms. Conclusions: The bystander protocol is a safe, effective method for testing in-development image guidance systems in human subjects.

Are 3D Image Guidance Systems Ready for Use? A Comparative Analysis of 3D Image Guidance Implementations in Minimally Invasive Partial Nephrectomy.

Introduction: Three-dimensional image-guided surgical (3D-IGS) systems for minimally invasive partial nephrectomy (MIPN) can potentially improve the efficiency and accuracy of intraoperative anatomical localization and tumor resection. This review seeks to analyze the current state of research regarding 3D-IGS, including the evaluation of clinical outcomes, system functionality, and qualitative insights regarding 3D-IGS's impact on surgical procedures. Methods: We have systematically reviewed the clinical literature pertaining to 3D-IGS deployed for MIPN. For inclusion, studies must produce a patient-specific 3D anatomical model from two-dimensional imaging. Data extracted from the studies include clinical results, registration (alignment of the 3D model to the surgical scene) method used, limitations, and data types reported. A subset of studies was qualitatively analyzed through an inductive coding approach to identify major themes and subthemes across the studies. Results: Twenty-five studies were included in the review. Eight (32%) studies reported clinical results that point to 3D-IGS improving multiple surgical outcomes. Manual registration was the most utilized (48%). Soft tissue deformation was the most cited limitation among the included studies. Many studies reported qualitative statements regarding surgeon accuracy improvement, but quantitative surgeon accuracy data were not reported. During the qualitative analysis, six major themes emerged across the nine applicable studies. They are as follows: 3D-IGS is necessary, 3D-IGS improved surgical outcomes, researcher/surgeon confidence in 3D-IGS system, enhanced surgeon ability/accuracy, anatomical explanation for qualitative assessment, and claims without data or reference to support. Conclusions: Currently, clinical outcomes are the main source of quantitative data available to point to 3D-IGS's efficacy. However, the literature qualitatively suggests the benefit of accurate 3D-IGS for robotic partial nephrectomy.

Unified Robot and Inertial Sensor Self-Calibration.

Robots and inertial measurement units (IMUs) are typically calibrated independently. IMUs are placed in purpose-built, expensive automated test rigs. Robot poses are typically measured using highly accurate (and thus expensive) tracking systems. In this paper, we present a quick, easy, and inexpensive new approach to calibrate both simultaneously, simply by attaching the IMU anywhere on the robot's end effector and moving the robot continuously through space. Our approach provides a fast and inexpensive alternative to both robot and IMU calibration, without any external measurement systems. We accomplish this using continuous-time batch estimation, providing statistically optimal solutions. Under Gaussian assumptions, we show that this becomes a nonlinear least squares problem and analyze the structure of the associated Jacobian. Our methods are validated both numerically and experimentally and compared to standard individual robot and IMU calibration methods.

Autonomous medical needle steering in vivo.

The use of needles to access sites within organs is fundamental to many interventional medical procedures both for diagnosis and treatment. Safely and accurately navigating a needle through living tissue to a target is currently often challenging or infeasible because of the presence of anatomical obstacles, high levels of uncertainty, and natural tissue motion. Medical robots capable of automating needle-based procedures have the potential to overcome these challenges and enable enhanced patient care and safety. However, autonomous navigation of a needle around obstacles to a predefined target in vivo has not been shown. Here, we introduce a medical robot that autonomously navigates a needle through living tissue around anatomical obstacles to a target in vivo. Our system leverages a laser-patterned highly flexible steerable needle capable of maneuvering along curvilinear trajectories. The autonomous robot accounts for anatomical obstacles, uncertainty in tissue/needle interaction, and respiratory motion using replanning, control, and safe insertion time windows. We applied the system to lung biopsy, which is critical for diagnosing lung cancer, the leading cause of cancer-related deaths in the United States. We demonstrated successful performance of our system in multiple in vivo porcine studies achieving targeting errors less than the radius of clinically relevant lung nodules. We also demonstrated that our approach offers greater accuracy compared with a standard manual bronchoscopy technique. Our results show the feasibility and advantage of deploying autonomous steerable needle robots in living tissue and how these systems can extend the current capabilities of physicians to further improve patient care.

Toward Continuum Robot Tentacles for Lung Interventions: Exploring Folding Support Disks.

Toward the future goal of creating a lung surgery system featuring multiple tentacle-like robots, we present a new folding concept for continuum robots that enables them to squeeze through openings smaller than the robot's nominal diameter (e.g., the narrow space between adjacent ribs). This is facilitated by making the disks along the robot's backbone foldable. We also demonstrate that such a robot can feature not only straight, but also curved tendon routing paths, thereby achieving a diverse family of conformations. We find that the foldable robot performs comparably, from a kinematic perspective, to an identical non-folding continuum robot at varying deployment lengths. This work paves the way for future applications with a continuum robot that can fold and fit through smaller openings, with the potential to reduce invasiveness during surgical tasks.

Robotic pullback technique of a precurved cochlear-implant electrode array using real-time impedance sensing feedback.

PURPOSE: During traditional insertion of cochlear implant (CI) electrode arrays (EAs), surgeons rely on limited tactile feedback and visualization of the EA entering the cochlea to control the insertion. One insertion approach for precurved EAs involves slightly overinserting the EA and then retracting it slightly to achieve closer hugging of the modiolus. In this work, we investigate whether electrical impedance sensing could be a valuable real-time feedback tool to advise this pullback technique. METHODS: Using a to-scale 3D-printed scala tympani model, a robotic insertion tool, and a custom impedance sensing system, we performed experiments to assess the bipolar insertion impedance profiles for a cochlear CI532/632 precurved EA. Four pairs of contacts from the 22 electrode contacts were chosen based on preliminary testing and monitored in real time to halt the robotic insertion once the closest modiolar position had been achieved but prior to when the angular insertion depth (AID) would be reduced. RESULTS: In this setting, the open-loop robotic insertion impedance profiles were very consistent between trials. The exit of each contact from the external stylet of this EA was clearly discernible on the impedance profile. In closed-loop experiments using the pullback technique, the average distance from the electrode contacts to the modiolus was reduced without greatly affecting the AID by using impedance feedback in real time to determine when to stop EA retraction. CONCLUSION: Impedance sensing, and specifically the access resistance component of impedance, could be a valuable real-time feedback tool in the operating room during CI EA insertion. Future work should more thoroughly analyze the effects of more realistic operating room conditions and inter-patient variability on this technique.

A Metric for Finding Robust Start Positions for Medical Steerable Needle Automation.

Steerable needles are medical devices with the ability to follow curvilinear paths to reach targets while circumventing obstacles. In the deployment process, a human operator typically places the steerable needle at its start position on a tissue surface and then hands off control to the automation that steers the needle to the target. Due to uncertainty in the placement of the needle by the human operator, choosing a start position that is robust to deviations is crucial since some start positions may make it impossible for the steerable needle to safely reach the target. We introduce a method to efficiently evaluate steerable needle motion plans such that they are safe to variation in the start position. This method can be applied to many steerable needle planners and requires that the needle's orientation angle at insertion can be robotically controlled. Specifically, we introduce a method that builds a funnel around a given plan to determine a safe insertion surface corresponding to insertion points from which it is guaranteed that a collision-free motion plan to the goal can be computed. We use this technique to evaluate multiple feasible plans and select the one that maximizes the size of the safe insertion surface. We evaluate our method through simulation in a lung biopsy scenario and show that the method is able to quickly find needle plans with a large safe insertion surface.

Transeustachian Middle Ear Endoscopy Using a Steerable Distal-Camera Tipped Endoscope.

OBJECTIVE: Demonstrate the ability of a novel steerable distal chip endoscope to traverse the Eustachian tube and provide diagnostic quality images of the human middle ear. PATIENTS: Three cadaveric temporal bone specimens were used in this work. INTERVENTION: Diagnostic transeustachian endoscopy of the middle ear was performed. MAIN OUTCOME MEASURE: Diagnostic image quality. RESULTS: A novel 1.62 mm steerable endoscope successfully cannulated the Eustachian tube of three human cadaveric temporal bone specimens to reveal intact middle ear anatomy with high optical clarity. CONCLUSIONS: A steerable endoscope can be designed to traverse the human Eustachian tube and provide diagnostic quality images of middle ear anatomy.

Patient-specific, touch-based registration during robotic, image-guided partial nephrectomy.

Image-guidance during partial nephrectomy enables navigation within the operative field alongside a 3-dimensional roadmap of renal anatomy generated from patient-specific imaging. Once a process is performed by the human mind, the technology will allow standardization of the task for the benefit of all patients undergoing robot-assisted partial nephrectomy. Any surgeon will be able to visualize the kidney and key subsurface landmarks in real-time within a 3-dimensional simulation, with the goals of improving operative efficiency, decreasing surgical complications, and improving oncologic outcomes. For similar purposes, image-guidance has already been adopted as a standard of care in other surgical fields; we are now at the brink of this in urology. This review summarizes touch-based approaches to image-guidance during partial nephrectomy, as the technology begins to enter in vivo human evaluation. The processes of segmentation, localization, registration, and re-registration are all described with seamless integration into the da Vinci surgical system; this will facilitate clinical adoption sooner.

Design Considerations for a Steerable Needle Robot to Maximize Reachable Lung Volume.

Steerable needles that are able to follow curvilinear trajectories and steer around anatomical obstacles are a promising solution for many interventional procedures. In the lung, these needles can be deployed from the tip of a conventional bronchoscope to reach lung lesions for diagnosis. The reach of such a device depends on several design parameters including the bronchoscope diameter, the angle of the piercing device relative to the medial axis of the airway, and the needle's minimum radius of curvature while steering. Assessing the effect of these parameters on the overall system's clinical utility is important in informing future design choices and understanding the capabilities and limitations of the system. In this paper, we analyze the effect of various settings for these three robot parameters on the percentage of the lung that the robot can reach. We combine Monte Carlo random sampling of piercing configurations with a Rapidly-exploring Random Trees based steerable needle motion planner in simulated human lung environments to asymptotically accurately estimate the volume of sites in the lung reachable by the robot. We highlight the importance of each parameter on the overall system's reachable workspace in an effort to motivate future device innovation and highlight design trade-offs.

Closed-loop control of soft continuum manipulators under tip follower actuation.

Continuum manipulators, inspired by nature, have drawn significant interest within the robotics community. They can facilitate motion within complex environments where traditional rigid robots may be ineffective, while maintaining a reasonable degree of precision. Soft continuum manipulators have emerged as a growing subfield of continuum robotics, with promise for applications requiring high compliance, including certain medical procedures. This has driven demand for new control schemes designed to precisely control these highly flexible manipulators, whose kinematics may be sensitive to external loads, such as gravity. This article presents one such approach, utilizing a rapidly computed kinematic model based on Cosserat rod theory, coupled with sensor feedback to facilitate closed-loop control, for a soft continuum manipulator under tip follower actuation and external loading. This approach is suited to soft manipulators undergoing quasi-static deployment, where actuators apply a follower wrench (i.e., one that is in a constant body frame direction regardless of robot configuration) anywhere along the continuum structure, as can be done in water-jet propulsion. In this article we apply the framework specifically to a tip actuated soft continuum manipulator. The proposed control scheme employs both actuator feedback and pose feedback. The actuator feedback is utilized to both regulate the follower load and to compensate for non-linearities of the actuation system that can introduce kinematic model error. Pose feedback is required to maintain accurate path following. Experimental results demonstrate successful path following with the closed-loop control scheme, with significant performance improvements gained through the use of sensor feedback when compared with the open-loop case.

Backward Planning for a Multi-Stage Steerable Needle Lung Robot.

Lung cancer is one of the deadliest types of cancer, and early diagnosis is crucial for successful treatment. Definitively diagnosing lung cancer typically requires biopsy, but current approaches either carry a high procedural risk for the patient or are incapable of reaching many sites of clinical interest in the lung. We present a new sampling-based planning method for a steerable needle lung robot that has the potential to accurately reach targets in most regions of the lung. The robot comprises three stages: a transorally deployed bronchoscope, a sharpened piercing tube (to pierce into the lung parenchyma from the airways), and a steerable needle able to navigate to the target. Planning for the sequential deployment of all three stages under health safety concerns is a challenging task, as each stage depends on the previous one. We introduce a new backward planning approach that starts at the target and advances backwards toward the airways with the goal of finding a piercing site reachable by the bronchoscope. This new strategy enables faster performance by iteratively building a single search tree during the entire computation period, whereas previous forward approaches have relied on repeating this expensive tree construction process many times. Additionally, our method further reduces runtime by employing biased sampling and sample rejection based on geometric constraints. We evaluate this approach using simulation-based studies in anatomical lung models. We demonstrate in comparison with existing techniques that the new approach (i) is more likely to find a path to a target, (ii) is more efficient by reaching targets more than 5 times faster on average, and (iii) arrives at lower-risk paths in shorter time.

Clinical Translation of an Insertion Tool for Minimally Invasive Cochlear Implant Surgery.

The objective of this paper is to describe the development of a minimally invasive cochlear implant surgery (MICIS) electrode array insertion tool concept to enable clinical translation. First, analysis of the geometric parameters of potential MICIS patients (N = 97) was performed to inform tool design, inform MICIS phantom model design, and provide further insight into MICIS candidacy. Design changes were made to the insertion tool based on clinical requirements and parameter analysis results. A MICIS phantom testing model was built to evaluate insertion force profiles in a clinically realistic manner, and the new tool design was evaluated in the model and in cadavers to test clinical viability. Finally, after regulatory approval, the tool was used for the first time in a clinical case. Results of this work included first, in the parameter analysis, approximately 20% of the population was not considered viable MICIS candidates. Additionally, one 3D printed tool could accommodate all viable candidates with polyimide sheath length adjustments accounting for interpatient variation. The insertion tool design was miniaturized out of clinical necessity and a disassembly method, necessary for removal around the cochlear implant, was developed and tested. Phantom model testing revealed that the force profile of the insertion tool was similar to that of traditional forceps insertion. Cadaver testing demonstrated that all clinical requirements (including complete disassembly) were achieved with the tool, and the new tool enabled 15% deeper insertions compared to the forceps approach. Finally, and most importantly, the tool helped achieve a full insertion in its first MICIS clinical case. In conclusion, the new insertion tool provides a clinically viable solution to one of the most difficult aspects of MICIS.

Magnetic Steering of Robotically Inserted Lateral-wall Cochlear-implant Electrode Arrays Reduces Forces on the Basilar Membrane In Vitro.

HYPOTHESIS: Undesirable forces applied to the basilar membrane during surgical insertion of lateral-wall cochlear-implant electrode arrays (EAs) can be reduced via robotic insertion with magnetic steering of the EA tip. BACKGROUND: Robotic insertion of magnetically steered lateral-wall EAs has been shown to reduce insertion forces in vitro and in cadavers. No previous study of robot-assisted insertion has considered force on the basilar membrane. METHODS: Insertions were executed in an open-channel scala-tympani phantom. A force plate, representing the basilar membrane, covered the channel to measure forces in the direction of the basilar membrane. An electromagnetic source generated a magnetic field to steer investigational EAs with permanent magnets at their tips, while a robot performed the insertion. RESULTS: When magnetic steering was sufficient to pull the tip of the EA off of the lateral wall of the channel, it resulted in at least a 62% reduction of force on the phantom basilar membrane at insertion depths beyond 14.4 mm (p < 0.05), and these beneficial effects were maintained beyond approximately the same depth, even with 10 degrees of error in the estimation of the modiolar axis of the cochlea. When magnetic steering was not sufficient to pull the EA tip off of the lateral wall, a significant difference from the no-magnetic-steering case was not found. CONCLUSIONS: This in vitro study suggests that magnetic steering of robotically inserted lateral-wall cochlear-implant EAs, given sufficient steering magnitude, can reduce forces on the basilar membrane in the first basilar turn compared with robotic insertion without magnetic steering.

Beyond Constant Curvature: A New Mechanics Model for Unidirectional Notched-Tube Continuum Wrists.

This paper presents a new mechanics model for unidirectional notched-tube continuum wrists, a class of mechanisms frequently used to implement distal steering in needle-sized surgical robotic instruments. Existing kinematic models available for these devices are based on the simplifying assumption that, during actuation, all the notches undergo the same amount of deflection, so that the shape of a wrist can be approximated by an arc of constant curvature. This approach is analytically attractive, but, as we show in this paper, it can sometimes fail to provide good tracking accuracy. In this article, we provide a new model that relaxes the assumption above, and we report experimental evidence showing its superior accuracy. We model wrist deflection using Castigliano's second theorem, with the addition of a capstan friction term that accounts for frictional losses on the actuation tendon. Because notched-tube wrists are typically made of Nickel-Titanium (Nitinol), which has nonlinear stress-strain characteristics, we use a technique to obtain a local linearized approximation of the material modulus, suitable for use in the deflection model. The result of our modeling is a system of nonlinear equations that can be solved numerically to predict the wrist configuration based on the applied actuation force. Experimental results on physical specimens show that this improved model provides a more accurate estimate of wrist kinematics than prior models assuming constant curvature bending.

Eyes in Ears: A Miniature Steerable Digital Endoscope for Trans-Nasal Diagnosis of Middle Ear Disease.

The aim of this work is to design, fabricate and experimentally validate a miniature steerable digital endoscope that can provide comprehensive, high-resolution imaging of the middle ear using a trans-nasal approach. The motivation for this work comes from the high incidence of middle ear diseases, and the current reliance on invasive surgery to diagnose and survey these diseases which typically consists of the eardrum being lifted surgically to directly visualize the middle ear using a trans-canal approach. To enable less-invasive diagnosis and surveillance of middle ear disease, we propose an endoscope that is small enough to pass into the middle ear through the Eustachian tube, with a steerable tip that carries a 1 Megapixel image sensor and fiber-optic illumination to provide high-resolution visualization of critical middle ear structures. The proposed endoscope would enable physicians to diagnose middle ear disease using a non-surgical trans-nasal approach instead, enabling such procedures to be performed in an office setting and greatly reducing invasiveness for the patient. In this work, the computational design of the steerable tip based on computed tomography models of real human middle ear anatomy is presented, and these results informed the fabrication of a clinical-scale steerable endoscope prototype. The prototype was used in a pilot study in three cadaveric temporal bone specimens, where high-quality middle ear visualization was achieved as determined by an unbiased cohort of otolaryngologists. This is the first paper to demonstrate cadaveric validation of a digital, steerable, clinical-scale endoscope for middle ear disease diagnosis, and the experimental results illustrate that the endoscope enables the visualization of critical middle ear structures (such as the epitympanum or sinus tympani) that were seldom or never visualized in prior published trans-Eustachian tube endoscopy feasibility studies.

Accuracy of Touch-Based Registration During Robotic Image-Guided Partial Nephrectomy Before and After Tumor Resection in Validated Phantoms.

Aim: Image-guided surgery (IGS) allows for accurate, real-time localization of subsurface critical structures during surgery. No prior IGS systems have described a feasible method of intraoperative reregistration after manipulation of the kidney during robotic partial nephrectomy (PN). We present a method for seamless reregistration during IGS and evaluate accuracy before and after tumor resection in two validated kidney phantoms. Materials and Methods: We performed robotic PN on two validated kidney phantoms-one with an endophytic tumor and one with an exophytic tumor-with our IGS system utilizing the da Vinci Xi robot. Intraoperatively, the kidney phantoms' surfaces were digitized with the da Vinci robotic manipulator via a touch-based method and registered to a three-dimensional segmented model created from cross-sectional CT imaging of the phantoms. Fiducial points were marked with a surgical marking pen and identified after the initial registration using the robotic manipulator. Segmented images were displayed via picture-in-picture in the surgeon console as tumor resection was performed. After resection, reregistration was performed by reidentifying the fiducial points. The accuracy of the initial registration and reregistration was compared. Results: The root mean square (RMS) averages of target registration error (TRE) were 2.53 and 4.88 mm for the endophytic and exophytic phantoms, respectively. IGS enabled resection along preplanned contours. Specifically, the RMS averages of the normal TRE over the entire resection surface were 0.75 and 2.15 mm for the endophytic and exophytic phantoms, respectively. Both tumors were resected with grossly negative margins. Point-based reregistration enabled instantaneous reregistration with minimal impact on RMS TRE compared with the initial registration (from 1.34 to 1.70 mm preresection and from 1.60 to 2.10 mm postresection). Conclusions: We present a novel and accurate registration and reregistration framework for use during IGS for PN with the da Vinci Xi surgical system. The technology is easily integrated into the surgical workflow and does not require additional hardware.