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Abstract
Advances in robotic medicine have been adopted by various surgical subspecialties as the benefits of this technology become more readily apparent: precision in narrow operative windows, tremor controlled movements, and modestly improved outcomes, among others. Vascular neurosurgery, in particular, remains open to newer and more cutting edge treatment options for complex pathologies, and robotics may be on the horizon for such advances. We seek to provide a broad overview of these innovations in vascular neurosurgery for both practitioners well acquainted with robotics and those seeking to become more familiar. Technologies under development for cerebrovascular and endovascular neurosurgery include robot assisted angiography, guided operative microscopes, coil insertion systems, and endoscopic clipping devices. Additionally, robotic systems in the fields of interventional cardiology and radiology have potential applications to endovascular neurosurgery but require proper modifications to navigate complex intracerebral vasculature. Robotic technology is not without drawbacks, as broad implementation may lead to increased cost, training time, and potential delays in emergency situations. Further cultivation of current multidisciplinary technologies and investment into newer systems is necessary before robotics can make a sizable impact in clinical practice.
- endovascular
- robot-assisted surgery
- robotics technology
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Introduction
Robotic technology has been increasingly embraced by many surgical specialties over the past decade. Its utility in improving standard techniques and enabling novel minimally invasive procedures has been demonstrated by observed declines in morbidity and mortality and improved clinical outcomes.1 2 Important advantages to robot assisted or computer assisted surgery include overcoming human limitations, increasing consistency in surgical technique, eradicating hurdles associated with conventional surgical and interventional instruments, mitigating the need for complex postoperative care for patients, and improving surgeon safety.3
One such specialty beginning to incorporate robotics into clinical practice is neurosurgery.4–6 Robots are capable of minuscule, tremor filtered movements and cannot become fatigued—assets that are invaluable to the realm of micro-neurosurgery, particularly when manipulating delicate intracranial structures via narrow corridors. Furthermore, the introduction of robot assisted neurosurgery has provided surgeons with enhanced dexterity, superior visualization, and improved tactile capabilities.6 The current applications of robotics in neurosurgery have proven useful in preoperative, intraoperative, and postoperative imaging, surgical treatment of neuro-oncological diseases, implant placement in spine procedures, and stereotactic electroencephalography.7–9
Although interest in utilizing robotics to improve neurosurgical procedures has steadily risen, there remains a paucity of data and descriptive reporting in the subspecialty of cerebrovascular and endovascular neurosurgery. As clinical technologies in this field are rapidly evolving (ie, development of mini-open or minimally invasive surgical techniques; intrasaccular devices and flow diverting stents for aneurysm treatment), there is great potential for the expansion and incorporation of robotic technology. Therefore, we sought to provide a broad review of the current status of robotics in cerebrovascular and endovascular neurosurgery and to offer future perspectives into technologies that have vascular applications to neurosurgery.
Classification of medical robots
Two main systems exist to describe medical robotic technology: the technical and interaction classifications. From a technical standpoint, medical application of robots falls under passive or active effector modules. In passive effector robotics, the surgeon primarily acts to drive surgical tools and provides the main action in the intervention; the robot acts primarily to hold fixtures at pre-designated locations to maintain operative precision and augment the acquisition of a defined surgical target (ie, use in stereotactic procedures). In active effector robotics, the robot plays a more intimate and forward role in surgical action by completing more complex movements. While the robot in this type of system has greater autonomy, the surgeon has the capability of overseeing the entire procedure and may intervene when necessary.10
The classification of medical robots by surgeon–machine interaction includes supervisory controlled, teleoperated, and shared control systems. Supervisory controlled robots, like the Neuromate stereotactic robot (Renishaw, Wotton-under-Edge, UK), are programmable machines that are set to follow specific movements, which are pre-planned offline by the operating physician. From there, the robot completes the preset motions autonomously while under surveillance.5 Teleoperated robots, also referred to as ‘master–slave’ systems, incorporate a surgical module under direct control by a surgeon. The surgeon provides real time input to a command console, usually through a force feedback joystick (master), while the surgical manipulator executes the actions faithfully (slave). The widely used da Vinci Surgical System (Intuitive Surgical, Sunnyvale, California, USA) is a current paradigm for teleoperated systems.11 Finally, in shared control systems, such as the Steady Hand Eye Robot (CIIS Laboratory, Baltimore, Maryland, USA), the surgeon shares control of the surgical instrument with the robot. In this type of synergistic modality, the surgeon remains fully in control of the surgical instrument, but the robot provides ‘steady hand’ manipulation in real time.12
Developing cerebrovascular and neuroendovascular robotic technology
The development of robotics for use in cerebrovascular and endovascular neurosurgery is a recent endeavor and includes a variety of technologies designed for different procedures (table 1). While some of these technologies have undergone more robust testing than others, all are in the experimental stages and do not represent the current standard of care. However, the technologies we describe display promise for further research and clinical implementation.
Current literature regarding robotic technologies specifically for cerebrovascular and endovascular neurosurgery, with a description of the advantages and disadvantages
Cerebral angiography
Robotic technology has been used by several different groups to perform diagnostic cerebral angiography. Lu et al detailed a vascular interventional robot with two components: a mechanical propulsion system inside the operating room to drive catheter advancement and a remote guidance system outside of the operating room controlled by the surgeon.13 Cerebral angiography was successfully performed on 15 patients using this robotic system, all without complications. This study demonstrated that guidance of the catheter from a remote position is feasible in cerebrovascular and endovascular cases, and reduces radiation exposure to surgical staff.
Additionally, Murayama et al described a robotic digital subtraction angiography (DSA) system that uses a multi-axis C arm with rotational three-dimensional imaging capabilities.14 This system creates real time three-dimensional angiographic images that allow for more precise visualization of, and catheter guidance through, complex vasculature. If necessary, the flexible C arm also facilitates rapid conversion of endovascular procedures to open surgery without repositioning the patient. The robotic DSA system was successfully utilized during 501 neurosurgical procedures, including many endovascular cases, such as coil embolization and intraoperative angiography.
Robot assisted operating microscope
A robotic, auto-navigating operating microscope was recently evaluated for use in neurosurgical procedures, including the treatment of arteriovenous malformations and cavernous malformations by Bohl et al.15 The microscope can be automatically positioned to lock onto a predetermined target, focus on various targets throughout a surgical procedure defined by the particular focal length and position of the microscope, or sync with neuro-navigation software to follow a predefined trajectory based on a given surgical plan. In a prospective cohort of 20 patients, 9 of whom had either arteriovenous malformation or cavernous malformation, no complications occurred on integration of the auto-navigation technology into otherwise routine surgical procedures. Setup time for the microscope was less than 1 min in all cases. This study indicated that robotic microscope positioning technology is safe and has the potential to improve surgical efficacy and efficiency.
Mechanical coil insertion systems
A mechanical coil insertion system has been introduced by Haraguchi et al for endovascular treatment of intracranial aneurysms.16 Their work is based on experiments by Matsubara et al that demonstrated a smaller coil insertion force achieved with mechanical insertion at a constant speed versus manual insertion, and laid the groundwork for further study of robotics in coil embolization.17 18 The system described by Haraguchi et al enables one surgeon to manipulate both the microcatheter and delivery wire or coil, a task typically performed by two surgeons.16 The delivery unit includes a driving roller, which propels the delivery wire at adjustable insertion speeds (0.5, 1.0, 1.5, or 2.0 mm/s), and a foot pedal to move the wire forward or backwards. The operator manipulates the microcatheter and judges the insertion force via a sensor. The device was successfully tested in vitro using silicone dummy aneurysms and demonstrated no complications.
Endoscopic surgical clipping
Kato et al described the development of a two section continuum robot with a wide angle view and flexible tip positioning for endoscopic clipping of intracranial aneurysms.19 In vitro experiments demonstrated that the two section continuum robot achieved larger viewing angles than a one section endoscope, which indicates that it might allow for greater visualization in the area around an aneurysm without disruption of the surrounding neurovasculature in vivo.
Current technology with potential neurovascular applications
While several advanced robotic systems are currently under development for direct application to cerebrovascular and endovascular neurosurgery, a variety of technologies exist for clinical use. At present, many robotic technologies in interventional cardiology and radiology are utilized for the treatment of central and peripheral vascular pathologies (table 2). However, there is great potential for their inclusion into, and specific modification for, cerebrovascular and neuroendovascular procedures.
Summary of selected Food and Drug Administration approved robotic technology in interventional cardiology and radiology, with potential applications to cerebrovascular and endovascular neurosurgery
Robotic technology in interventional cardiology
There are several Food and Drug Administration (FDA) approved cardiovascular interventional units, three of which we describe here: (1) the electromechanical based Sensei Robotic System (Hansen Medical, Mountain View, California, USA), (2) the Niobe Magnetic Navigation System (Stereotaxis, St Louis, Missouri, USA), and (3) the Amigo Remote Catheter System (RCS) (Catheter Robotics, Mount Olive, New Jersey, USA).20–22 The Sensei system, which was initially designed to facilitate navigation and positioning of catheters for collection of electrophysiological data, consists of the surgeon workstation, the remote catheter manipulator, and a console specific steerable catheter called the Artisan Extend Control Catheter (Hansen Medical). The master console, which can be placed away from the patient and radiation source, uses a multidirectional, hand operated joystick to transmit the surgeon’s movements to the remote control unit fixed near the patient, thereby directing the catheter. In one report, the Sensei system with Artisan catheters was used in 40 endovascular radiofrequency ablation procedures to treat atrial fibrillation and atrial flutter. Apart from the apparent efficacy of robotic assisted catheter interventions, this type of system provided superior catheter stability and larger df for catheter movement.23
The Niobe system utilizes a magnetic field produced by two computer controlled magnets to propel and direct a catheter. By changing the orientation and strength of the magnetic field, the catheter, equipped with magnetic implants at the tip, can be controlled remotely. While the Niobe system requires a specific 0.014 inch diameter guidewire (from Stereotaxis), it can be used with 7 or 8 F catheters with up to 120o bend radius. As with the Sensei system, the Niobe navigation unit was used successfully to perform completely remote controlled mapping and ablation in patients with cardiac pathologies.24
The Amigo RCS is mechanistically similar to the electromechanical Sensei system. The construct utilizes a catheter fixed to a remote controlled arm placed in close proximity to the patient, while the actual remote controller is a hand held device that provides multidirectional input to drive the catheter. Unique to the Amigo is the wide array of catheters that can be fixed into the system; with the Sensei system, only proprietary catheters can be utilized. According to a non-randomized, prospective clinical trial of 206 participants (NCT No 01139814), the Amigo RCS had zero major complications, no unanticipated adverse events, and no vascular perforations in studies testing the ease of catheter placement.25
Peripheral catheter guidance technologies
In addition to the Sensei, Niobe, and Amigo systems, there are multiple robotic catheter guidance platforms designated for peripheral use: (1) the Magellan Robotic System (Hansen Medical) and (2) the CorPath 200 System (Corindus Vascular Robotics, Waltham, Massachusetts, USA). The Magellan Robotic System is based on the original Sensei system but incorporates major modifications, including a newer catheter that is smaller, more flexible, and has a more adaptable coaxial catheter system. The 6.5 F leader catheter, with 180o multidirectional articulation, and the 9.5 F sheath, with an additional 90o articulation, are controlled by an operator from a remote workstation. The robotic manipulator similarly allows for insertion, rotation, and retraction of conventional 0.018 inch and 0.035 inch hydrophilic wires. Riga et al reported the efficacy of the Magellan system in the endovascular repair of a 7.3 cm juxtarenal aneurysm, noting no intraoperative complications.26
The CorPath 200 System, although first cleared for use in percutaneous coronary interventions, was recently awarded FDA approval for percutaneous vascular interventional procedures. In this apparatus, a physician interacts with the joystick or touch screen of the control console that drives the main surgical manipulator closer to the patient. Major advantages with this system include positioning of the robotic controller behind a radiation barrier, which mitigates radiation exposure to the user, as well as its compatibility with a variety of commercially available guidewires and catheters. In the RAPID (Robotic Assisted Peripheral Intervention for peripheral arterial Disease) study (NCT No 02371785), the CorPath 200 System was successfully used to perform peripheral arterial revascularization of 20 patients with a total of 29 lesions, all without complications.27
While the aforementioned technologies may eventually be integrated into neuroendovascular practice, the current limitations to translational efforts are primarily associated with their specific design for cardiovascular and peripheral vascular interventions. Intracerebral vessels are considerably smaller and more tortuous than those implicated in cardiac and peripheral pathologies, making it particularly important that robotic systems in endovascular neurosurgery are created with the appropriate size, maneuverability, and feedback mechanisms to safely navigate through such delicate structures. Modification of current technology would require smaller catheter and guidewire components with enhanced precision and control to ensure that a variety of neurovascular pathologies can be effectively treated. Thus, application to neurosurgical procedures may take further time and development. That said, these technologies present an interesting potential for the introduction of robotic catheter guidance systems into neurovascular interventions, and are duly included in this review.
Discussion
Robot assisted cerebrovascular and endovascular neurosurgery
Advantages
Robotic technology in cerebrovascular and endovascular neurosurgery is burgeoning, and has proven advantageous in procedures involving catheter guidance, intraoperative imaging, and neuronavigation. First, it allows for increased safety for both patients and surgeons. From the patient perspective, in addition to clear benefits associated with augmented operative control and consistency, robotic systems that incorporate force measurements and respond in real time to stay below a predetermined threshold may help in preventing vessel puncture and damage to delicate structures. Surgeons benefit as well, because of their ability to remotely control robots away from the radiation source. Additionally, robotic catheter guidance systems confer many advantages, such as improved stability and greater freedom of motion, which make them applicable to complex embolization procedures for the treatment of arteriovenous malformations, fistulas, and tumors, and would be especially useful in the navigation of tortuous anatomy commonly seen in older patients. The aforementioned FDA approved endovascular units unequivocally demonstrate the utility of robotic catheter systems and provide a groundwork from which technologies specific for neurosurgery may eventually develop. As a result of enhanced surgical precision and resistance to fatigue, robotic technologies also display an improved ability to minimize incisions and surgical corridors in cranial and aneurysm surgery. Finally, robots show increased efficiency in both intraoperative angiography and combined endovascular and open vascular procedures.
Disadvantages
The integration of robots into cerebrovascular and neuroendovascular practice is not without potential complications, however. As with any new technology, cost is a limiting factor. The research, development, manufacturing, and maintenance of highly complex robotic systems is an expensive endeavor, and widespread incorporation of these technologies would require a significant investment on the parts of hospitals and healthcare systems. Cost aside, the training of both surgeons and surgical support staff on proper and proficient usage of new robotic systems is likely a lengthy process, involving a steep learning curve and frequent practice for the refinement of surgical skills. Additionally, introduction of robotic technology has the potential to change the dynamic within the operating room and disrupt operative flow, particularly in emergency situations. Although remote control of robotic interventional units minimizes surgeons’ exposure to radiation, the additional time it would take to transition from endovascular to open surgery in an emergency could prove deleterious for the patient, depending on the specific situation.
Finally, an important limitation to current robotic systems is the lack of tactile feedback. Surgeons rely on this feedback in both open vascular and endovascular cases. As a result, some endovascular practitioners prefer to perform procedures by hand, and some open vascular surgeons prefer to retract with their instruments rather than employ stationary retractors. Current systems eliminate this advantage, so before clinicians can comfortably use robots in practice, this drawback must be addressed. That being said, we are seeing up and coming technologies incorporate force sensors to provide some procedural feedback to operators, specifically in mechanical coil insertion.16 Such a feature is a prime example of the continued innovation we expect to see in the future.
Future perspectives
Robotic applications to cerebrovascular and endovascular neurosurgery are still in their infancy. As more technologies are designed, developed, and tested, several important factors must be taken into consideration. First, an appropriate balance between surgical control and robotic autonomy is imperative for safe integration, utilization, and adaptation to changing surgical conditions. While robotic systems undeniably allow for increased precision and demonstrate exceptional endurance, they lack the training, experience, and human judgment necessary to make real time, consequential surgical decisions, especially in a discipline as highly technical as vascular neurosurgery. In order to better elucidate the ways in which robots can augment cerebrovascular and neuroendovascular care without assuming complete surgical authority, more studies with well defined parameters for efficacy and safety should be conducted. This applies both to novel technologies and to current non-neurological robotic systems, such as the Sensei and Niobe, that demonstrate potential for use in neurosurgery. Adaptation of current vascular robotic technology to fit the specific requirements of neurovascular interventions displays the most promise for increasing clinical implementation.
Overall, we believe that integrating robots into practice will add another layer into the expertise needed to perform neurointerventional surgery, as opposed to detract from skills needed to perform procedures safely and successfully. Proper bedside etiquette vital to patient care and the capability to take operative control in emergency situations will always be important. Undoubtedly, robots cannot efface the core tenets of the physician–patient relationship. However, clinicians may be expected in the future to decide which patients can benefit from robotic augmented techniques, and apply risk/benefit assessment to individual cases based on operator and robot limitations.
Conclusions
Robotic technology in vascular neurosurgery remains on the horizon for broader clinical use, limited by logistical considerations, relative paucity in experimental data, and possible delays in emergency situations. Nonetheless, with advances in operative technique and crossover from fields such as interventional cardiology, there is potential for robotics to make meaningful impacts in neurointerventional surgery. Technologies under development for cerebrovascular and endovascular neurosurgery include robot assisted angiography, guided operative microscopes, coil insertion systems, and endoscopic clipping devices. At this stage though, more investigation and greater collaboration between various interventional fields employing robotics are warranted.
References
Footnotes
Contributors SAM, SSS, BMS, and SS contributed to the conception, literature review, and drafting of the manuscript. RMS and ECP provided manuscript oversight and administrative support. All authors critically reviewed the manuscript and approved its final submission.
Funding This research received no specific grant from any funding agency in the public, commercial or not for profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.