Mechatronic Design of a Two-Arm Concentric Tube Robot System for Rigid Neuroendoscopy

Magnetically actuated dexterous tools for minimally invasive operation inside the brain

Operating in the brain for deep-seated tumors or surgical targets for epilepsy is technically demanding and normally requires a large craniotomy with its attendant risk and morbidity. Neuroendoscopic surgery has the potential to reduce risk and morbidity by permitting surgical access through a small incision with burr hole and a narrow corridor through the brain. However, current endoscopic neurosurgical tools are straight and rigid and lack dexterity, hindering their adoption for neuroendoscopic procedures. We propose a class of robotic neurosurgical tools that have magnetically actuated wristed end effectors small enough to fit through a neuroendoscope working channel. The tools were less than 3.2 millimeters in overall diameter and contained embedded permanent magnets that allowed wireless actuation with magnetic fields. Three magnetic tools are presented: a two-degrees-of-freedom (DoFs) wristed gripper, a one-DoF pivoting scalpel, and a one-DoF twisted string-actuated forceps. This work evaluated the feasibility of these tools for completing minimally invasive neurosurgical resection and cutting tasks. Experimental tests on a silicone brain phantom showed that the tools could reach the ventricle area for simulated tumor removal and access a section of the corpus callosotomy for a simulated tissue-severing procedure in epilepsy treatment. Integration of the magnetic end effectors with a concentric tube robot as a hybrid steerable surgical robotic system enabled in vivo experiments on piglets. These experiments show that wireless magnetic tools could perform essential neurosurgical tasks, including gripping, cutting, and biopsy on living brain tissue, suggesting their potential for clinical applications.

Evaluation of current and emerging endoluminal robotic platforms using the IDEAL framework

BACKGROUND

Robotic-assisted endoluminal systems are rapidly evolving within the field of minimally invasive surgery. The IDEAL framework (Idea, Development, Exploration, Assessment, and Surveillance) can be used to evaluate novel technologies. This review provides a summary of current and emerging endoluminal systems using the IDEAL framework.

METHODS

A scoping review was conducted to include all existing and developing robotic-assisted endoluminal systems. Data was collected via virtual interviews, questionnaires, biomedical databases, company websites, and peer-reviewed articles. Key metrics were reported, enabling the assignment of each system to an IDEAL stage.

RESULTS

The review identified 17 distinct systems from 16 companies. Nine systems received regulatory approval in their respective countries. Our evaluation showed that two systems were at the pre-IDEAL Stage 0. Seven systems were in the Idea stage (Stage 1), six systems were in the Development stage (Stage 2) and two systems completed Stage 3. No system underwent long-term study evaluation (Stage 4).

CONCLUSIONS

There is a gap in long-term clinical data of robotic-assisted endoluminal systems, indicated by the absence of systems at Stage 4. Collaborative efforts amongst the medical community, regulatory bodies, and industry specialists are vital to ensure the delivery of evidence-based medicine in the discipline of robotics.

Boiling Histotripsy in Ex Vivo Human Brain: Proof-of-concept

OBJECTIVE

Non-invasive surgical approaches, including boiling histotripsy (BH), are currently being developed for the treatment of brain disorders aiming to avoid craniotomy and exposure of intervening tissues, and, thus, minimize associated complications. This work aimed to demonstrate the feasibility of BH for mechanical fractionation of human brain tissues ex vivo under B-mode guidance, with preliminary measurements of tissue stiffness via shear wave elastography.

METHODS

Young's moduli of 25 human autopsy brain samples obtained from de-identified patients of 51-91 y old (median 77 y old) were measured via shear wave elastography prior to BH sonication. Seventeen volumetric BH lesions (1-4 layers of 5 × 5 points with a 1- mm step) were produced near brain surface (n = 10), in white matter (n = 3), in thalamus (n = 2), and globus pallidus (n = 2) using 12 element 1.5 MHz sector transducer under B-mode guidance with 10 ms or 2 ms pulses delivered 10 or 15 times per sonication point with 1% duty cycle. After treatment, the lesions were evaluated grossly through bisection, histologically with hematoxylin and eosin staining, and ultrastructurally via scanning and transmission electron microscopy.

RESULTS

Young's moduli of autopsy brain samples were lower in older patients (from 32.9 ± 6.6 kPa in 51 y olds to 10 ± 2 kPa in 91 y olds) and at higher temperature (6%-50% lower at 37°С vs 23°С), and were within the range observed clinically. All tested BH treatments performed near the brain surface (i.e., mostly in gray matter) resulted in formation of well-demarcated rectangular lesions with homogenized content and sharp boundaries, with majority of residual fragments below 100 microns. The use of shorter pulses (2 ms vs 10 ms) accelerated the treatment at least threefold, and the highest liquefaction rate was 568 mm3/min. White matter was more resistant to BH vs gray matter: at least 15 pulses of 2 ms duration were required per each sonication point, and the liquefaction rate was three times lower. The ability of BH to produce lesions in thalamus and globus pallidus was also confirmed.

CONCLUSION

This work presents the first demonstration of BH proof-of-concept in human brain tissues ex vivo under B-mode guidance with clinically relevant treatment rates.

Hierarchical Containment Control With Bipartite Cluster Consensus for Heterogeneous Multiagent Systems Under Layer-Signed Digraph

This article considers the hierarchical containment control (HCC) for flexible mirrored collaboration, which accommodates the bipartite cluster consensus behavior in two symmetric convex hulls formed by multiple leaders. First, to achieve the mirrored collaboration in symmetric convex hulls, the layer-signed digraph is generated by involving the antagonistic interaction. Benefiting from the hierarchical structure, the antagonistic interaction in the assistant-layer replaces the assumption of in-degree balance for the existing cluster consensus issues. Second, the existing types of control protocols and the framework of cooperative output regulation limit the achievement of the studied hierarchical mirrored collaboration. To solve this problem, the hierarchical cooperative output regulation is extended based on the formulated hierarchical mirrored collaborative errors. Third, the layer-signal compensator is designed estimating the states of leaders as well as guaranteeing the convergence of collaborative behaviors. Combining with the designed layer-signal compensator, a novel HCC protocol is proposed so that the bipartite cluster consensus behavior can be achieved simultaneously in two symmetric convex hulls. Finally, theoretical results are verified by performing the numerical simulation.

Development of a single port dual arm robotically steerable endoscope for neurosurgical applications

Single-port surgical robots have gained popularity due to less patient trauma and quicker post-surgery recovery. However, due to limited access provided by a single incision, the miniaturization and maneuverability of these robots still needs to be improved. In this paper, we propose the design of a single-port, dual-arm robotically steerable endoscope containing one steerable major cannula and two steerable minor cannulas. By integrating the proposed nine degrees-of-freedom (DoFs) robotically steerable endoscope with an industrial robotic arm and a joystick controller, this robotic system can potentially achieve intuitive, and remote multi-arm manipulation capability. We present the design of the robotically steerable endoscope consisting of tendon-driven joints controlled by a compact actuation system and derive the kinematic and static models. We validate the derived models using different kinematic trajectories with an average RMSE value of 0.98 mm and 0.66 mm for the distal tip position errors of the two steerable minor cannulas.

Non-Metallic MR-Guided Concentric Tube Robot for Intracerebral Hemorrhage Evacuation

OBJECTIVE

We aim to develop and evaluate an MR-conditional concentric tube robot for intracerebral hemorrhage (ICH) evacuation.

METHODS

We fabricated the concentric tube robot hardware with plastic tubes and customized pneumatic motors. The robot kinematic model was developed using a discretized piece-wise constant curvature (D-PCC) approach to account for variable curvature along the tube shape, and tube mechanics model was used to compensate torsional deflection of the inner tube. The MR-safe pneumatic motors were controlled using a variable gain PID algorithm. The robot hardware was validated in a series of bench-top and MRI experiments, and the robot's evacuation efficacy was tested in MR-guided phantom trials.

RESULTS

The pneumatic motor was able to achieve a rotational accuracy of 0.32°±0.30° with the proposed variable gain PID control algorithm. The kinematic model provided a positional accuracy of the tube tip of 1.39 ± 0.54 mm. The robot was able to evacuate an initial 38.36 mL clot, leaving a residual hematoma of 8.14 mL after 5 minutes, well below the 15 mL guideline suggesting good post-ICH evacuation clinical outcomes.

CONCLUSION

This robotic platform provides an effective method for MR-guided ICH evacuation.

SIGNIFICANCE

ICH evacuation is feasible under MRI guidance using a plastic concentric tube, indicating potential feasibility in future live animal studies.

The Future of Neuroendoscopy: Looking Ahead Through a Lens

Neuroendoscopy has progressed remarkably in the past few decades. Ventriculoscopy, skull base endoscopy, and spinal endoscopy are now part of routine practice in the neurosurgical treatment of numerous pathologies. Like other developing fields, however, it faces numerous challenges and obstacles that must be overcome for the field to continue to evolve and expand. This brief review of new and exciting developments in neuroendoscopy describes some of the most interesting directions the field is starting to steer towards.

Using robotics to move a neurosurgeon's hands to the tip of their endoscope

A major advantage of surgical robots is that they can reduce the invasiveness of a procedure by enabling the clinician to manipulate tools as they would in open surgery but through small incisions in the body. Neurosurgery has yet to benefit from this advantage. Although clinical robots are available for the least invasive neurosurgical procedures, such as guiding electrode insertion, the most invasive brain surgeries, such as tumor resection, are still performed as open manual procedures. To investigate whether robotics could reduce the invasiveness of major brain surgeries while still providing the manipulation capabilities of open surgery, we created a two-armed joystick-controlled endoscopic robot. To evaluate the efficacy of this robot, we developed a set of neurosurgical skill tasks patterned after the steps of brain tumor resection. We also created a patient-derived brain model for pineal tumors, which are located in the center of the brain and are normally removed by open surgery. In comparison, testing with existing manual endoscopic instrumentation, we found that the robot provided access to a much larger working volume at the trocar tip and enabled bimanual tasks without compression of brain tissue adjacent to the trocar. Furthermore, many tasks could be completed faster with the robot. These results suggest that robotics has the potential to substantially reduce the invasiveness of brain surgery by enabling certain procedures currently performed as open surgery to be converted to endoscopic interventions.

Development of a 3D Printed Brain Model with Vasculature for Neurosurgical Procedure Visualisation and Training

BACKGROUND

Simulation-based techniques using three-dimensional models are gaining popularity in neurosurgical training. Most pre-existing models are expensive, so we felt a need to develop a real-life model using 3D printing technology to train in endoscopic third ventriculostomy.

METHODS

The brain model was made using a 3D-printed resin mold from patient-specific MRI data. The mold was filled with silicone Ecoflex™ 00-10 and mixed with Silc Pig® pigment additives to replicate the color and consistency of brain tissue. The dura mater was made from quick-drying silicone paste admixed with gray dye. The blood vessels were made from a silicone 3D-printed mold based on magnetic resonance imaging. Liquid containing paprika oleoresin dye was used to simulate blood and was pumped through the vessels to simulate pulsatile motion.

RESULTS

Seven residents and eight senior neurosurgeons were recruited to test our model. The participants reported that the size and anatomy of the elements were very similar to real structures. The model was helpful for training neuroendoscopic 3D perception and navigation.

CONCLUSIONS

We developed an endoscopic third ventriculostomy training model using 3D printing technology that provides anatomical precision and a realistic simulation. We hope our model can provide an indispensable tool for young neurosurgeons to gain operative experience without exposing patients to risk.

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.

Impedance Iterative Learning Backstepping Control for Output-Constrained Multisection Continuum Arms Based on PMA

BACKGROUND

Pneumatic muscle actuator (PMA) actuated multisection continuum arms are widely applied in various fields with high flexibility and bionic properties. Nonetheless, their kinematic modeling and control strategy proves to be extremely challenging tasks.

METHODS

The relationship expression between the deformation parameters and the length of PMA with the geometric method is obtained under the assumption of piecewise constant curvature. Then, the kinematic model is established based on the improved D-H method. Considering the limitation of PMA telescopic length, an impedance iterative learning backstepping control strategy is investigated. For one thing, the impedance control is utilized to ensure that the ideal static balance force is maintained constant in the Cartesian space. For another, the iterative learning backstepping control is applied to guarantee that the desired trajectory of each PMA can be accurately tracked with the output-constrained requirement. Moreover, iterative learning control (ILC) is implemented to dynamically estimate the unknown model parameters and the precondition of zero initial error in ILC is released by the trajectory reconstruction. To further ensure the constraint requirement of the PMA tracking error, a log-type barrier Lyapunov function is employed in the backstepping control, whose convergence is demonstrated by the composite energy function.

RESULTS

The tracking error of PMA converges to 0.004 m and does not exceed the time-varying constraint function through cosimulation.

CONCLUSION

From the cosimulation results, the superiority and validity of the proposed theory are verified.

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.

Endoscopic Coregistered Ultrasound Imaging and Precision Histotripsy: Initial In Vivo Evaluation

Objective. Initial performance evaluation of a system for simultaneous high-resolution ultrasound imaging and focused mechanical submillimeter histotripsy ablation in rat brains. Impact Statement. This study used a novel combination of high-resolution imaging and histotripsy in an endoscopic form. This would provide neurosurgeons with unprecedented accuracy in targeting and executing nonthermal ablations in minimally invasive surgeries. Introduction. Histotripsy is a safe and effective nonthermal focused ablation technique. However, neurosurgical applications, such as brain tumor ablation, are difficult due to the presence of the skull. Current devices are too large to use in the minimally invasive approaches surgeons prefer. We have developed a combined imaging and histotripsy endoscope to provide neurosurgeons with a new tool for this application. Methods. The histotripsy component had a 10 mm diameter, operating at 6.3 MHz. Affixed within a cutout hole in its center was a 30 MHz ultrasound imaging array. This coregistered pair was used to ablate brain tissue of anesthetized rats while imaging. Histological sections were examined, and qualitative descriptions of ablations and basic shape descriptive statistics were generated. Results. Complete ablations with submillimeter area were produced in seconds, including with a moving device. Ablation progress could be monitored in real time using power Doppler imaging, and B-mode was effective for monitoring post-ablation bleeding. Collateral damage was minimal, with a 100 μm maximum distance of cellular damage from the ablation margin. Conclusion. The results demonstrate a promising hardware suite to enable precision ablations in endoscopic procedures or fundamental preclinical research in histotripsy, neuroscience, and cancer.

Biopsy Needle System With a Steerable Concentric Tube and Online Monitoring of Electrical Resistivity and Insertion Forces

OBJECTIVE

Biopsies are the gold standard for clinical diagnosis. However, a discrepancy between the biopsy sample and target tissue because of misplacement of the biopsy spoon can lead to errors in the diagnosis and subsequent treatment. Thus, correctly determining whether the needle tip is in the tumor is crucial for accurate biopsy results.

METHODS

A biopsy needle system was designed with a steerable, flexible, and superelastic concentric tube; electrodes to monitor the electrical resistivity; and load cells to monitor the insertion force. The degrees of freedom were analyzed for two working modes: straight-line and deflection.

RESULTS

Experimental results showed that the system could perceive the tissue type in online based on the electrical resistivity. In addition, changes in the insertion force indicated transitions between the interfaces of adjacent tissue layers.

CONCLUSION

The two monitoring methods guarantee that the biopsy spoon is at the desired position inside the tumor during an operation.

SIGNIFICANCE

The proposed biopsy needle system can be integrated into an autonomous robotic biopsy system.

Transurethral Anastomosis after Transurethral Radical Prostatectomy: A Phantom Study on Intraluminal Suturing With Concentric Tube Robots

Current surgical approaches to radical prostatectomy are associated with high rates of erectile dysfunction and incontinence. These complications occur secondary to the disruption of surrounding healthy tissue, which is required to expose the prostate. The urethra offers the least invasive access to the prostate, and feasibility has been demonstrated of enucleating the prostate with an endoscope using Holmium laser, which can itself be aimed by concentric tube robots. However, the transurethral approach to radical prostatectomy has thus far been limited by the lack of a suitable means to perform an anastomosis of the urethra to the bladder after prostate removal. Only a few intraluminal anastomotic devices currently exist, and none are small enough to pass through the urethra. In this paper we describe a new way to perform an anastomosis in the small luminal space of the urethra, harnessing the dexterity and customizability of concentric tube manipulators. We demonstrate a successful initial proof-of-concept anastomosis in an anthropomorphic phantom of the urethra and bladder.