Stereotactic Systems for MRI-Guided Neurosurgeries: A State-of-the-Art Review

Body-Mounted MR-Conditional Robot for Minimally Invasive Liver Intervention

MR-guided microwave ablation (MWA) has proven effective in treating hepatocellular carcinoma (HCC) with small-sized tumors, but the state-of-the-art technique suffers from sub-optimal workflow due to the limited accuracy provided by the manual needle insertions. This paper presents a compact body-mounted MR-conditional robot that can operate in closed-bore MR scanners for accurate needle guidance. The robotic platform consists of two stacked Cartesian XY stages, each with two degrees of freedom, that facilitate needle insertion pose control. The robot is actuated using 3D-printed pneumatic turbines with MR-conditional bevel gear transmission systems. Pneumatic valves and control mechatronics are located inside the MRI control room and are connected to the robot with pneumatic transmission lines and optical fibers. Free-space experiments indicated robot-assisted needle insertion error of 2.6 ± 1.3 mm at an insertion depth of 80 mm. The MR-guided phantom studies were conducted to verify the MR-conditionality and targeting performance of the robot. Future work will focus on the system optimization and validations in animal trials.

MR-Safe Cartesian Platform for Active Cardiac Shimming: Preliminary Validation

OBJECTIVE

Implanted Cardioverter Defibrillators (ICDs) induce a large (100 parts per million) inhomogeneous magnetic field in the magnetic resonance imaging (MRI) scanner which cannot be corrected by the scanner's built-in shim coils, leading to significant image artifacts that can make portions of the heart unreadable. To compensate for the field inhomogeneity, an active shim coil capable of countering the field deviation in user-defined regions was designed that must be optimally placed at patient-specific locations. We aim to develop and evaluate an MR-safe robotic solution for automated shim coil positioning.

METHODS

We designed and fabricated an MR-safe Cartesian platform that holds the shim coil inside the scanner. The platform consists of three lead screw stages actuated by pneumatic motors, achieving decoupled translations of 140 mm in each direction. The platform is made of plastics and fiberglass with the control electronics placed outside the scanner room, ensuring MR safety. Mechanical modeling was derived to provide design specifications.

RESULTS

Experiments show that the platform achieves less than 2 mm average motion error and 0.5 mm repeatability in all directions, and reduces the adjustment time from 5 min to a few seconds. Phantom and animal trials were conducted, showing that the proposed system is able to position a heavy shim coil ( kg) for improved ICD artifact suppression.

CONCLUSION

This robotic platform provides an effective method for reliable shim coil positioning inside the scanner.

SIGNIFICANCE

This work contributes to improving cardiac MRI quality that could facilitate accurate diagnosis and treatment planning for patients with implanted ICDs.

Towards MR-Guided Robotic Intracerebral Hemorrhage Evacuation: Aiming Device Design and ex vivo Ovine Head Trial

Stereotactic neurosurgery is a well-established surgical technique for navigation and guidance during treatment of intracranial pathologies. Intracerebral hemorrhage (ICH) is an example of various neurosurgical conditions that can benefit from stereotactic neurosurgery. As a part of our ongoing work toward real-time MR-guided ICH evacuation, we aim to address an unmet clinical need for a skull-mounted frameless stereotactic aiming device that can be used with minimally invasive robotic systems for MR-guided interventions. In this paper, we present NICE-Aiming, a Neurosurgical, Interventional, Configurable device for Effective-Aiming in MR-guided robotic neurosurgical interventions. A kinematic model was developed and the system was used with a concentric tube robot (CTR) for ICH evacuation in (i) a skull phantom and (ii) in the first ever reported ex vivo CTR ICH evacuation using an ex vivo ovine head. The NICE-Aiming prototype provided a tip accuracy of 1.41±0.35 mm in free-space. In the MR-guided gel phantom experiment, the targeting accuracy was 2.07±0.42 mm and the residual hematoma volume was 12.87 mL (24.32% of the original volume). In the MR-guided ex vivo ovine head experiment, the targeting accuracy was 2.48±0.48 mm and the residual hematoma volume was 1.42 mL (25.08% of the original volume).

Evolving Therapeutic Landscape of Intracerebral Hemorrhage: Emerging Cutting-Edge Advancements in Surgical Robots, Regenerative Medicine, and Neurorehabilitation Techniques

Intracerebral hemorrhage (ICH) is the most serious form of stroke and has limited available therapeutic options. As knowledge on ICH rapidly develops, cutting-edge techniques in the fields of surgical robots, regenerative medicine, and neurorehabilitation may revolutionize ICH treatment. However, these new advances still must be translated into clinical practice. In this review, we examined several emerging therapeutic strategies and their major challenges in managing ICH, with a particular focus on innovative therapies involving robot-assisted minimally invasive surgery, stem cell transplantation, in situ neuronal reprogramming, and brain-computer interfaces. Despite the limited expansion of the drug armamentarium for ICH over the past few decades, the judicious selection of more efficacious therapeutic modalities and the exploration of multimodal combination therapies represent opportunities to improve patient prognoses after ICH.

Interactive Multi-Stage Robotic Positioner for Intra-Operative MRI-Guided Stereotactic Neurosurgery

Magnetic resonance imaging (MRI) demonstrates clear advantages over other imaging modalities in neurosurgery with its ability to delineate critical neurovascular structures and cancerous tissue in high-resolution 3D anatomical roadmaps. However, its application has been limited to interventions performed based on static pre/post-operative imaging, where errors accrue from stereotactic frame setup, image registration, and brain shift. To leverage the powerful intra-operative functions of MRI, e.g., instrument tracking, monitoring of physiological changes and tissue temperature in MRI-guided bilateral stereotactic neurosurgery, a multi-stage robotic positioner is proposed. The system positions cannula/needle instruments using a lightweight (203 g) and compact (Ø97 × 81 mm) skull-mounted structure that fits within most standard imaging head coils. With optimized design in soft robotics, the system operates in two stages: i) manual coarse adjustment performed interactively by the surgeon (workspace of ±30°), ii) automatic fine adjustment with precise (<0.2° orientation error), responsive (1.4 Hz bandwidth), and high-resolution (0.058°) soft robotic positioning. Orientation locking provides sufficient transmission stiffness (4.07 N/mm) for instrument advancement. The system's clinical workflow and accuracy is validated with lab-based (<0.8 mm) and MRI-based testing on skull phantoms (<1.7 mm) and a cadaver subject (<2.2 mm). Custom-made wireless omni-directional tracking markers facilitated robot registration under MRI.

Microsurgery Robots: Applications, Design, and Development

Microsurgical techniques have been widely utilized in various surgical specialties, such as ophthalmology, neurosurgery, and otolaryngology, which require intricate and precise surgical tool manipulation on a small scale. In microsurgery, operations on delicate vessels or tissues require high standards in surgeons' skills. This exceptionally high requirement in skills leads to a steep learning curve and lengthy training before the surgeons can perform microsurgical procedures with quality outcomes. The microsurgery robot (MSR), which can improve surgeons' operation skills through various functions, has received extensive research attention in the past three decades. There have been many review papers summarizing the research on MSR for specific surgical specialties. However, an in-depth review of the relevant technologies used in MSR systems is limited in the literature. This review details the technical challenges in microsurgery, and systematically summarizes the key technologies in MSR with a developmental perspective from the basic structural mechanism design, to the perception and human-machine interaction methods, and further to the ability in achieving a certain level of autonomy. By presenting and comparing the methods and technologies in this cutting-edge research, this paper aims to provide readers with a comprehensive understanding of the current state of MSR research and identify potential directions for future development in MSR.

MRI-Conditional Eccentric-Tube Injection Needle: Design, Fabrication, and Animal Trial

Effective radiation therapy aims to maximize the radiation dose delivered to the tumor while minimizing damage to the surrounding healthy tissues, which can be a challenging task when the tissue-tumor space is small. To eliminate the damage to healthy tissue, it is now possible to inject biocompatible hydrogels between cancerous targets and surrounding tissues to create a spacer pocket. Conventional methods have limitations in poor target visualization and device tracking. In this paper, we leverage our MR-tracking technique to develop a novel injection needle for hydrogel spacer deployment. Herein, we present the working principle and fabrication method, followed by benchtop validation in an agar phantom, and MRI-guided validation in tissue-mimic prostate phantom and sexually mature female swine. Animal trials indicated that the spacer pockets in the rectovaginal septum can be accurately visualized on T2-weighted MRI. The experimental results showed that the vaginal-rectal spacing was successfully increased by 12 ± 2 mm anterior-posterior.

Towards a Closed-loop Neuro-Robotic Approach to DBS Electrode Implantation based on Real-Time Wrist Rigidity Evaluation

The iHandU system is a wearable device that quantitatively evaluates changes in wrist rigidity during Deep Brain Stimulation (DBS) surgery, allowing clinicians to find optimal stimulation settings that reduce patient symptoms. Robotic accuracy is also especially relevant in DBS surgery, as accurate electrode placement is required to increase effectiveness and reduce side effects. The main goal of this work is to integrate the advantages of each system in a closed-loop system between an industrial robot and the iHandU system. For this purpose, a comparative analysis of a Leksell stereotactic frame and neuro-robotic system accuracies was performed using a lab-made phantom. The neuro-robotic system reached 90% of trajectories, while the stereotactic frame reached all trajectories. There are significant differences in accuracy errors between these trajectories (p < 0.0001), which can be explained by the high correlation between the neuro-robotic system errors and the distance from the trajectory to the origin of the Leksell coordinate system (ρ = 0.72). Overall accuracy is comparable to existing neuro-robotic systems, achieving a deviation of (1.0 ± 0.5) mm at the target point. The accuracy of DBS electrode positioning and stimulation parameters choice leads to better long-term clinical outcomes in Parkinson's disease patients. Our neuro-robotic system combines real-time feedback assessment of the patient's symptomatic response and automatic positioning of the DBS electrode in a specific brain area.

Minimally Invasive Intracerebral Hemorrhage Evacuation: A review

Intracerebral hemorrhage is a leading cause of morbidity and mortality worldwide. To date, there is no specific treatment that clearly provides a benefit in functional outcome or mortality. Surgical treatment for hematoma evacuation has not yet shown clear benefit over medical management despite promising preclinical studies. Minimally invasive treatment options for hematoma evacuation are under investigation but remain in early-stage clinical trials. Robotics has the potential to improve treatment. In this paper, we review intracerebral hemorrhage pathology, currently available treatments, and potential robotic approaches to date. We also discuss the future role of robotics in stroke treatment.

A multi-degree-of-freedom clamping type traveling-wave ultrasonic motor

This paper proposes a multi-degree-of-freedom (multi-DOF) ultrasonic motor with four stators clamping a spherical rotor. The stator surface teeth are inclined at a certain angle, using the inclined surface to contact the rotor and transfer energy. The motor frame is exquisitely designed in which substrates hold four identical stators to drive the rotor to achieve a multi-DOF rotation. COMSOL Multiphysics performs the stator's modal analysis and harmonic response analysis to illustrate the vibration mode and frequency response. A prototype is fabricated to verify the operating principle and conduct the performance tests. The experimental results indicate that the motor can reach a no-load speed of 100r/min, and the stalling torque is 150mNm under a preload of 113 N. The results also denote the motor has a high load-carrying capacity with a maximum load torque of 143mNm and accurate operation with a maximum error of 0.15 mm.

A Brief Insight on Magnetic Resonance Conditional Neurosurgery Robots

The brain is a delicate organ in the human body that requires extreme care. Brain-related diseases are unavoidable. Perse, neurosurgery is a complicated procedure that demands high precision and accuracy. Developing a surgical robot is a complex task. To date, there are only a handful of neurosurgery robots in the market that distinctly undergo clinical procedures. These robots have exorbitant cost that hinders the utmost care progress in the area as they are unaffordable. This paper looked at the historical perspective and presented insight literature of the magnetic resonance conditional stereotactic neurosurgery robots that find their ways in clinics, abandoning research projects and promising research yet to undergo clinical use. In addition, the study also gives a thorough insight into the advantage of magnetic resonance imaging modalities and magnetic resonance conditional robots and the future challenges in automation use. Image compatibility test data and accuracy results are also examined because they guarantee that these systems work correctly in particular imaging settings. The primary differences between these systems include actuation and control technologies, construction materials, and the degree of freedom. Thus, one system has an advantage over the other.

A Historical Review of Medical Robotic Platforms

This paper provides a brief history of medical robotic systems. Since the first use of robots in medical procedures, there have been countless companies competing to developed robotic systems in hopes to dominate a field. Many companies have succeeded, and many have failed. This review paper shows the timeline history of some of the old and most successful medical robots and new robotic systems. As the patents of the most successful system, i.e., Da Vinci® Surgical System, have expired or are expiring soon, this paper can provide some insights for new designers and manufacturers to explore new opportunities in this field.

Review of Advanced Medical Telerobots

The advent of telerobotic systems has revolutionized various aspects of the industry and human life. This technology is designed to augment human sensorimotor capabilities to extend them beyond natural competence. Classic examples are space and underwater applications when distance and access are the two major physical barriers to be combated with this technology. In modern examples, telerobotic systems have been used in several clinical applications, including teleoperated surgery and telerehabilitation. In this regard, there has been a significant amount of research and development due to the major benefits in terms of medical outcomes. Recently telerobotic systems are combined with advanced artificial intelligence modules to better share the agency with the operator and open new doors of medical automation. In this review paper, we have provided a comprehensive analysis of the literature considering various topologies of telerobotic systems in the medical domain while shedding light on different levels of autonomy for this technology, starting from direct control, going up to command-tracking autonomous telerobots. Existing challenges, including instrumentation, transparency, autonomy, stochastic communication delays, and stability, in addition to the current direction of research related to benefit in telemedicine and medical automation, and future vision of this technology, are discussed in this review paper.

MR-Conditional Actuations: A Review

Magnetic resonance imaging (MRI) is one of the most prevailing technologies to enable noninvasive and radiation-free soft tissue imaging. Operating a robotic device under MRI guidance is an active research area that has the potential to provide efficient and precise surgical therapies. MR-conditional actuators that can safely drive these robotic devices without causing safety hazards or adversely affecting the image quality are crucial for the development of MR-guided robotic devices. This paper aims to summarize recent advances in actuation methods for MR-guided robots and each MR-conditional actuator was reviewed based on its working principles, construction materials, the noteworthy features, and corresponding robotic application systems, if any. Primary characteristics, such as torque, force, accuracy, and signal-to-noise ratio (SNR) variation due to the variance of the actuator, are also covered. This paper concludes with a perspective on the current development and future of MR-conditional actuators.

Development of a Stereotactic Radiosurgery Frame Adapter for a Multichannel MRI Coil

BACKGROUND

The usage of multichannel brain MRI coils, which have several advantages over single-channel brain coils used for stereotactic radiosurgery (SRS), requires a frame adapter device to fit the frames inside the multichannel brain coils. However, such a frame adapter has not been developed until now.

OBJECTIVE

to develop an SRS frame adapter for multichannel MRI coils and verify the geometrical accuracy and signal-to-noise ratio (SNR) of the MR images obtained using multichannel MRI coils.

METHODS

We fabricated an SRS frame adapter for a 48-channel MRI coil using a three-dimensional (3D) printer. Furthermore, we obtained phantom and human-brain MR images with a 3.0 Tesla MRI scanner using multi- and single-channel coils. Computed tomography (CT) phantom images were also obtained as reference. We compared the coordinate errors of the multi- and single-channel coils to evaluate the geometrical accuracy. Two neurosurgeons measured the coordinates. In addition, we compared the SNR differences between multi- and single-channel coils using the T1- and T2-weighted brain images.

RESULTS

For the CT coordinate measurements, the correlation coefficient r = 1 and p < 0.001 with respect to the 3 axes (Δx, Δy, and Δz) and 3D errors (Δr) showed no interpersonal differences between the 2 neurosurgeons. The results obtained using the T1-weighted images showed that a multichannel coil had smaller coordinate errors in Δx, Δy, Δz, and Δr than that observed in case of a single-channel coil (p < 0.001). In case of the SNR measurements, most of the brain areas showed higher SNRs when using a multichannel coil compared with that observed when using a single-channel coil in the T1- and T2-weighted images.

CONCLUSION

Compared with single-channel coils, the use of multichannel MRI coils with a newly developed frame adapter is expected to ensure successful SRS treatments with improved geometrical accuracy and SNR.

Image-guided cochlear access by non-invasive registration: a cadaveric feasibility study

Image-guided cochlear implant surgery is expected to reduce volume of mastoidectomy, accelerate recovery, and improve safety. The purpose of this study was to investigate the safety and effectiveness of image-guided cochlear implant surgery by a non-invasive registration method, in a cadaveric study. We developed a visual positioning frame that can utilize the maxillary dentition as a registration tool and completed the tunnels experiment on 5 cadaver specimens (8 cases in total). The accuracy of the entry point and the target point were 0.471 ± 0.276 mm and 0.671 ± 0.268 mm, respectively. The shortest distance from the margin of the tunnel to the facial nerve and the ossicular chain were 0.790 ± 0.709 mm and 1.960 ± 0.630 mm, respectively. All facial nerves, tympanic membranes, and ossicular chains were completely preserved. Using this approach, high accuracy was achieved in this preliminary study, suggesting that the non-invasive registration method can meet the accuracy requirements for cochlear implant surgery. Based on the above accuracy, we speculate that our method can also be applied to neurosurgery, orbitofacial surgery, lateral skull base surgery, and anterior skull base surgery with satisfactory accuracy.