Steerable Tip Research Articles

An MRI-Conditional Flexible Endoscopic Robot with a Hydraulic Tendon-Driven Actuation System

This paper presents the conceptualization, mathematical modeling, and experimental validation of a magnetic resonance imaging (MRI)-conditional, flexible endoscopic robot for MRI-guided neurosurgery. The robotic assembly encompasses a straight rigid shaft, a tendon-driven steerable tip with two degrees of freedom, and a compact hybrid actuation system made of nonmagnetic modules. The robot’s small diameter, approximately 3 mm, allows for robot navigation through narrow cavities, such as nasal passages and the densely packed anatomy of the skull base. By filling the robot with deionized water, the MRI contrast of the robot can be improved, therefore enabling intra-operative tracking of the robot’s movement. In this paper, we present the design and fabrication process of the robotic system, kinematic analysis of the robot, and experimental studies to validate our model, characterize the robot, and test the feedback robot control. Furthermore, we demonstrate the MRI compatibility of the robot, along with the intra-operative tracking capability.

A Small Steerable Tip Based on Dielectric Elastomer Actuators

A Small Steerable Tip Based on Dielectric Elastomer Actuators

Toward a novel soft robotic system for minimally invasive interventions.

During minimally invasive surgery, surgeons maneuver tools through complex anatomies, which is difficult without the ability to control the position of the tools inside the body. A potential solution for a substantial portion of these procedures is the efficient design and control of a pneumatically actuated soft robot system. We designed and evaluated a system to control a steerable catheter tip. A macroscale 3D printed catheter tip was designed to have two separately pressurized channels to induce bending in two directions. A motorized hand controller was developed to allow users to control the bending angle while manually inserting the steerable tip. Preliminary characterization of two catheter tip prototypes was performed and used to map desired angle inputs into pressure commands. The integrated robotic system allowed both a novice and a skilled surgeon to position the steerable catheter tip at the location of cylindrical targets with sub-millimeter accuracy. The novice was able to reach each target within ten seconds and the skilled surgeon within five seconds on average. This soft robotic system enables its user to simultaneously insert and bend the pneumatically actuated catheter tip with high accuracy and in a short amount of time. These results show promise concerning the development of a soft robotic system that can improve outcomes in minimally invasive interventions.

Technical Feasibility and Safety of a Snare-Less, EVAR-First Technique for Iliac Branch Endoprosthesis.

The purpose of this study was to evaluate the technical feasibility, safety, and early outcomes of a snare-less, endovascular abdominal aortic aneurysm repair (EVAR)-first technique (SET) for iliac branch endoprosthesis (IBE) placement. We retrospectively reviewed all patients who received IBEs between July 2018 and March 2022. Patients were divided into 2 categories based on method of IBE deployment: SET or Standard. Primary endpoints were technical success, major adverse events, mortality, reintervention, internal iliac artery (IIA) patency, and freedom from IIA branch instability. Technical success was defined by successful deployment of both the EVAR and the IBE with maintained patency of the IIA and no stent graft migration. There were 20 patients (90% male, median age 72 [65.4-74.5] years) who underwent IBE placement. Among these, 5 (33.3%) underwent SET to treat 5 common iliac artery (CIA)/IIA aneurysms, while the remaining 15 (66.7%) underwent standard IBE deployment with through-and-through femoral access (n=13) or trans-brachial access (n=2) to treat 19 CIA/IIA aneurysms. Overall median renal to iliac bifurcation length was 169 (152-177) mm, with 9 patients falling short of the minimum of 165 mm for on-label IBE placement. Median contrast used was 148 (120-201) mL, fluoroscopy time 42.8 (35.0-49.8) minutes, estimated blood loss 200 (100-275) mL, and procedure time 192 (167-246) minutes, with no significant differences between the 2 groups. Technical success was achieved in 100% of cases. At 30 days, there were no mortalities or major adverse events in either group; there were 100% IIA patency, no IIA instability, and no reinterventions in both groups. Median follow-up in the SET group was 5.7 (5.5-6.2) months, with 1 death at 6 months and 1 type 1B endoleak at 6 months requiring reintervention. Median follow-up for the Standard group was 1.6 (0.8-2.1) years with 2 non-aneurysm-related deaths and no reinterventions at 1 year. SET for IBE is a safe and effective approach that decreases technical complexity and mitigates anatomic barriers to IBE placement. SET for IBE is a safe and effective approach to IBE placement that decreases technical complexity. A critical component to this technique is a large bore sheath with a stiff steerable tip. Importantly, this approach also mitigates anatomic barriers to IBE placement, expanding applicability of IBE technology to patients who may be otherwise ineligible.

Bend-insensitive fiber optic ultrasonic tracking probe for cardiovascular interventions.

Transesophageal echocardiography (TEE) is widely used to guide medical device placement in minimally invasive cardiovascular procedures. However, visualization of the device tip with TEE can be challenging. Ultrasonic tracking, enabled by an integrated fiber optic ultrasound sensor (FOUS) that receives transmissions from the TEE probe, is very well suited to improving device localization in this context. The problem addressed in this study is that tight deflections of devices such as a steerable guide catheter can result in bending of the FOUS beyond its specifications and a corresponding loss of ultrasound sensitivity. A bend-insensitive FOUS was developed, and its utility with ultrasonic tracking of a steerable tip during TEE-based image guidance was demonstrated. Fiberoptic ultrasound sensors were fabricated using both standard and bend insensitive single mode fibers and subjected to static bending at the distal end. The interference transfer function and ultrasound sensitivities were compared for both types of FOUS. The bend-insensitive FOUS was integrated within a steerable guide catheter, which served as an exemplar device; the signal-to-noise ratio (SNR) of tracking signals from the catheter tip with a straight and a fully deflected distal end were measured in a cardiac ultrasound phantom for over 100 frames. With tight bending at the distal end (bend radius<10mm), the standard FOUS experienced a complete loss of US sensitivity due to high attenuation in the fiber, whereas the bend-insensitive FOUS had largely unchanged performance, with a SNR of 47.7 for straight fiber and a SNR of 36.8 at a bend radius of 3.0mm. When integrated into the steerable guide catheter, the mean SNRs of the ultrasonic tracking signals recorded with the catheter in a cardiac phantom were similar for straight and fully deflected distal ends: 195 and 163. The FOUS fabricated from bend-insensitive fiber overcomes the bend restrictions associated with the FOUS fabricated from standard single mode fiber, thereby enabling its use in ultrasonic tracking in a wide range of cardiovascular devices.

The Cobra Catheter: A Novel Concept and Device for the Thru-Septal Myocardium Approach.

Objectives In our previous study, we suggested the novel septal traversing technique as effective and safe in catheter-based approach for septal myocardium. However, it is limited by its dependence on the septal perforator vein. This study aimed to evaluate the Cobra catheter as a backup catheter to overcome this limitation in swine. Methods We designed the guiding Cobra catheter. It consisted of three major parts (the external pull-wire steerable distal tip, the C-shaped shaft, and the steering adjustment handle). We tested the difference in force between the guidewire passing through the muscle and the vessel wall using a push-pull gauge. We performed a septal wire engage procedure in swine using the Cobra catheter. The guidewire engagement of the septal vein and Cobra catheter were compared visually and histopathologically. Results A total of ten swine were enrolled in this study. The success rate was 100% under fluoroscopy. The experiments confirmed the medical potential of the septal approach even in a location irrelevant to the septal perforator vein anatomy and confirmed that the wire passed well in the target direction in the harvested heart. There was no serious physical damage or pathological abnormalities in the vessel wall and myocardium. Conclusion These results showed that the novel Cobra catheter with a septal vein-independent trans-septal approach may be a safe and effective alternative for the treatment of structural heart diseases.

Steerable Surgical Instrument for Conventional and Single-Site Minimally Invasive Surgery.

Background. This article aims to present an innovative design of a steerable surgical instrument for conventional and single-site minimally invasive surgery (MIS), which improves the dexterity and maneuverability of the surgeon while offering a solution to the limitations of current tools. Methods. The steerable MIS instrument consists of a deflection structure with a curved sliding joints design that articulates the distal tip in two additional degrees of freedom (DoFs), relative to the instrument shaft, using transmission by cables. A passive ball-joint mechanism articulates the handle relative to the instrument shaft, improves wrist posture, and prevents collision of instrument handles during single-site MIS procedures. The two additional DoFs of the articulating tip are activated by a thumb-controlled device, using a joystick design mounted on the handle. This steerable MIS instrument was developed by additive manufacturing in a 3D printer using PLA polymer. Results. Prototype testing showed a maximum tip deflection of 60° in the left and right directions, with a total deflection of 120°. With the passive ball-joint fully offset, the steerable tip achieved a deflection of 90° for the right and 40° for the left direction, with a total deflection of 130°. Furthermore, the passive ball-joint mechanism in the handle obtained a maximum range of motion of 60°. Conclusions. This steerable MIS instrument concept offers an alternative to enhance the application fields of conventional and single-site MIS, increasing manual dexterity of the surgeon and the ability to reach narrow anatomies from other directions.

First Expert Evaluation of a New Steerable Catheter in an Isolated Beating Heart

PurposeIn previous studies we developed two mechanical prototypes of steerable catheters: the Sigma, which uses joysticks to actuate two steerable tip segments, and the Epsilon, which has a handle that is an enlarged version of the tip. In this study, we present a first performance evaluation of the prototypes in the cardiac environment. The evaluation was carried out by an expert user, an electrophysiologist with over 20 years of experience, to obtain insight in clinically relevant factors.MethodsTwo experiments were conducted. In the first experiment, the Sigma was used in a passive beating heart setup connected to pumps with a saline solution and camera visualization, and compared with the expert’s past experience with conventional steerable catheters. In the second experiment, the Sigma was used in an active beating heart setup with blood perfusion through the coronary arteries and echo visualization, and compared with the Epsilon prototype. The prototype was evaluated through questionnaires on task performance, catheter usability, and workload. After each of the experiments, the catheter characteristics were evaluated via a survey and followed by an in-depth interview.Results & ConclusionsThe expert user found the passive beating heart setup to more successful than the active beating heart setup for the purpose of this experiment, with insightful visualization while the heart was in beating condition. The steerability of the prototypes was experienced as useful and clinically relevant. Based on the questionnaires and interview we were able to identify future design improvements and developments for the steerable catheter prototypes.

Design, prototype development and pre-clinical validation of a novel instrument with a compliant steerable tip to facilitate endoscopic ear surgery

This work presents the design of a novel compliant steerable tip (CST) instrument to facilitate transcanal (or totally) endoscopic ear surgery (TEES). The evolution of the instrument’s design is shown, where prototypes were evaluated by surgeons and their feedback was used to inform the design changes for the next prototype iteration. The final prototype enables the surgeon to articulate the compliant tip to achieve the desired bending curvature while automatically locking in place and providing dissection and suction capabilities. Pre-clinical validation testing was performed in goat and human cadaver models by two surgeons who successfully removed an allograft from the middle ear. Time and the number of blockages while suctioning saline in both cadaver models were measured and compared with current instruments used during TEES. The CST took significantly less time to suction saline within a flooded middle ear compared to the Panetti suction dissector (PSD) for atticus and underwent less blockages than the PSD for atticus, ear drum and sinus tympani instruments, Wilcoxon Method p < .05. Our study demonstrates the development and successful clinical evaluation of a minimally invasive surgical instrument designed to facilitate endoscopic approaches to the ear.

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.

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.

Direct Writing of Elastic Fibers with Optical, Electrical, and Microfluidic Functionality

AbstractDirect Ink Writing is an additive fabrication technology that allows the integration of a diverse range of functional materials into soft and bioinspired devices such as robots and human‐machine interfaces. Typically, a viscoelastic ink is extruded from a nozzle as a continuous filament of circular cross section. Here it is shown that a careful selection of printing parameters such as nozzle height and speed can produce filaments with a range of cross‐sectional geometries. Thus, elliptic cylinder‐, ribbon‐, or groove‐shaped filaments can be printed. By using the nozzle as a stylus for postprint filament modification, even filaments with an embedded microfluidic channel can be produced. This strategy is applied to directly write freeform and elastic optical fibers, electrical interconnects, and microfluidics. The integration of these components into simple sensor‐actuator systems is demonstrated. Prototypes of an optical fiber with steerable tip and a thermal actuation system for soft tissues are presented.

Towards the Development of A Steerable and MRI-Compatible Cardiac Catheter for Atrial Fibrillation Treatment.

To treat atrial fibrillation (AFib), radiofrequency ablation is usually implemented with a cardiac catheter to block abnormal electrical signals from pulmonary veins. However, it is challenging to manipulate a passive catheter. In addition, the radiation exposure to patients under fluoroscopic guidance has been a concern. To address these two major issues, this work presents the development of a steerable and MRI-compatible cardiac catheter by using shape memory alloy (SMA) as an alternative interventional tool for AFib. The developed cardiac catheter is comprised of a passive and flexible tubing and a steerable tip. The tip is composed of multiple bending modules and each module is actuated by a pair of antagonistic SMA wires. To improve the MRI-compatibility of SMA actuators, the electric current required for SMA actuation is significantly reduced by developing a technique of conductive heating actuation. In this paper, the design and fabrication of the cardiac catheter are presented, followed by modeling the SMA bending module. The working performance of the SMA bending module is experimentally studied. In the end, a proof-of-concept demonstration of the cardiac catheter is performed in an explanted heart.

Electromagnetically Navigated In Situ Fenestration of Aortic Stent Grafts: Pilot Animal Study of a Novel Fenestrated EVAR Approach.

Assess electromagnetically guided in situ fenestration of juxtarenal aortic stent grafts in an in vivo model. Using a newly developed electromagnetic guidance system together with a modified, electromagnetically guidable catheter with steerable tip, an electromagnetically trackable guidewire and a custom in situ fenestrateable stent graft, a series of seven animal experiments was performed. In a swine model, stent grafts were placed juxtarenally, covering the renal arteries. Subsequently, the perfusion of the renal arteries was restored using electromagnetically guided in situ fenestration of the graft at the renal ostia followed by covered stent placement. Intervention times and technical success were assessed. The individual components were successfully combined for the animal experiments. Thirteen of fourteen fenestration experiments in seven animals were successful in restoring perfusion through in situ fenestration. Fenestration (catheter introduction-guidewire placement in renal artery across graft) could be achieved in on average 10.5 ± 9.2min, and subsequent covered stent placement (guidewire placement-covered stent placement) took on average 32.7 ± 17.5min. No significant differences between left and right side reperfusion times could be detected. Reperfusion in<30min was achieved in 3/14 attempts. Electromagnetically navigated in situ aortic fenestration for juxtarenal aortic stent grafts was feasible in a healthy animal model. Identified remaining challenges were: shortening the procedure to avoid long warm ischemia times, using an aortic aneurysm animal model, and improving the stability of the stent graft material.

The performance of rigid scopes for tracheal intubation: a randomised, controlled trial in patients with a simulated difficult airway.

We compared the Bonfils™ and SensaScope™ rigid fibreoptic scopes in 200 patients with a simulated difficult airway randomised to one of the two devices. A cervical collar inhibited neck movement and reduced mouth opening to a mean (SD) of 23 (3) mm. The primary outcome parameter was overall success of tracheal intubation; secondary outcomes included first-attempt success, intubation times, difficulty of intubation, fibreoptic view and side-effects. The mean (95% CI) overall success rate was 88 (80-94)% for the Bonfils and 89 (81-94)% for the SensaScope (p = 0.83). First-attempt intubation success rates were 63 (53-72)% for the Bonfils and 72 (62-81)% for the SensaScope (p = 0.17). Median (IQR [range]) intubation time was significantly shorter with the SensaScope (34 (20-84 [5-240]) s vs. 45 (25-134 [12-230]) s), and fibreoptic view was significantly better with the SensaScope (full view of the glottis in 79% with the SensaScope vs. 61% with the Bonfils). This might be explained by its steerable tip and the S-formed shape, contributing to better manoeuvrability. There were no differences in the difficulty of intubation or side-effects.

DEVELOPMENT OF A NOVEL STEERABLE BOUGIE

Background: This paper describes the development of a new airway device that will improve the speed and safety of endotracheal intubation in anaesthesia and critical care. Case of need, design specification and fabrication of the steerable bougie mechanism is discussed. Aims: Identify the need for a novel steerable bougie whilst considering technology readiness levels associated with medical device design. Analyse and produce suitable mechanisms utilising smart materials to increase device functionality aiding successful patient intubation procedures. Methods: This work describes the total design activity that contributes to the successful development of medical devices, from case of need, to smart material actuation mechanisms. Research focuses on identifying a suitable control mechanism to allow a steerable tip to be integrated into a bougie with a control device attached to the laryngoscope. Results: Data collected from a user group survey supported the development of a novel bougie, with better shape retention, variable rigidity within the tip, and an integrated steerable function. Analysis of several mechanisms, artificial muscles, and smart materials identified a cost-effective steerable mechanism that can be incorporated into a bougie. Conclusion: Users have defined a need for an improved bougie. Controlling smart materials and mechanisms, within the predefined dimensions, identified strengths and weaknesses associated with steerable functions. The performance of the selected mechanism for incorporation requires a high level of control to accurately steer a device within the human airway.

Steerable Guidewire for Magnetic Resonance Guided Endovascular Interventions

In endovascular interventions, thin, flexible instruments are inserted through the skin into the blood vessels to diagnose and treat various diseases of the vascular system. One drawback is that the instruments are difficult to maneuver in the desired direction due to limitations in shape and flexibility. Another disadvantage is that the interventions are performed under intermittent fluoroscopy/angiography imaging. Magnetic resonance imaging (MRI) may offer advantages over X-ray guidance. It presents a good soft tissue contrast without the use of nephrotoxic media or ionizing radiation. The aim of this study is to develop a guidewire that is compatible with MRI and includes a steerable segment at the tip. This added degree-of-freedom may improve the maneuverability of the devices thereby the efficiently and safety of the navigation. A 1.6 m (5 ft, 3 in.) long and 0.035 in. diameter guidewire that consists of MR compatible materials and has a flexible tip was designed. The only metallic part was a nitinol rod that was implemented at the distal flexible tip. To limit the risk of heating in the MRI, this rod was kept shorter than 30 mm. The tip could be deflected in one direction by pulling on a Dyneema wire that was placed in the lumen of the shaft of the guidewire. To drive the steerable tip, a handle that could be easily attached/detached from the instrument was designed and implemented. Using the handle, the tip of the 1.60 m long guidewire prototype could be actuated to reach angles from 30 deg to 250 deg. The handle could easily be placed on and removed from the guidewire, so conventional 0.035 in.–compatible catheters could slide over from the proximal end. However, in order to make the guidewire more efficient to enter a bifurcation, the stiffness of the tip should progressively increase from its proximal to its distal end. The guidewire was imaged in a 1.5T MRI using real-time imaging without producing artifacts that would have shaded the anatomy. It was possible to assemble a guidewire with a steerable segment in the required size, using MR compatible materials. Therefore, the current design is a promising proof of concept and allowed us to clearly identify the features that need to be improved in order to come to a clinically applicable instrument.

A Comprehensive Overview of Multi-Branched Instruments Intended for NOTES and SILS

A Comprehensive Overview of Multi-Branched Instruments Intended for NOTES and SILS

DragonFlex – Smart Steerable Laparoscopic Instrument

DragonFlex – Smart Steerable Laparoscopic Instrument

Developments in neuroendoscopy: trial of a miniature rigid endoscope with a multidirectional steerable tip camera in the anatomical lab

The aim of this study is to assess field of view, usability and applicability of a rigid, multidirectional steerable video endoscope (EndActive) in various intracranial regions relevant to neurosurgical practice. In four cadaveric specimens, frontolateral, pterional, transnasal (to sella and clivus), interhemispheric (transcallosal and retrocallosal) and retrosigmoid approaches as well as precoronal burr holes for ventriculoscopy were performed. Anatomical target structures were defined in each region. We assessed field of view as well as optical and ergonomic features of the prototype. The EndActive is a 4-mm-diameter rigid video (endo)scope with an integral image sensor comprising an embedded light source. The viewing direction in a range of 160° can either be controlled by the computer keyboard or a four-way joystick mounted to the handle section of the endoscope. The endoscopic imaging system allows the operator to simultaneously see both a 160° wide-angle view of the site and an inset of a specific region of interest. The surgeon can hold the device like a microsurgical instrument in one hand and control movements precisely due to its reduced weight and ergonomic shape. The multiplanar variable-view rigid endoscope proved to be useful for following anatomical structures (cranial nerves I-XII). The device is effective in narrow working spaces where movements jeopardize the delicate surrounding structures. The multiplanar variable viewing mechanism in a compact device offers advantages in terms of safety and ergonomics. Improving the usability will probably optimize the applicability of endoscopic techniques in neurosurgery.