Development of a Low-Profile, Piezoelectric Robot for MR-Guided Abdominal Needle Interventions

PURPOSE

Minimally invasive needle-based interventions are commonly used in cancer diagnosis and treatment, including procedures, such as biopsy, brachytherapy, and microwave ablation. Although MR-guided needle placement offers several distinct advantages, such as high-resolution target visualization and accurate device tracking, one of the primary limitations that affect its widespread adoption is the ergonomic constraints of the closed-bore MRI environment, requiring the patients to be frequently moved in and out to perform the needle-based procedures. This paper introduces a low-profile, body-mounted, MR-guided robot designed to address this limitation by streamlining the operation workflow and enabling accurate needle placement within the MRI scanner.

METHODS

The robot employs piezoelectric linear actuators and stacked Cartesian XY stages to precisely control the position and orientation of a needle guide. A kinematic model and control framework was developed to facilitate accurate targeting. Additionally, clinical workflow for the liver interventions was developed to demonstrate the robot's capability to replicate existing procedures. The proposed system was validated in benchtop environment and 3T MRI scanner to quantify the system performance.

RESULTS

Experimental validations conducted in free space demonstrated a position accuracy of 2.38 ± 0.94 mm and orientation error of 1.40 ± 2.89°. Additional tests to confirm MR-conditionality and MR-guided phantom placements were carried out to assess the system's performance and safety in MRI suite, yielding a position error of 2.01 ± 0.77 mm and an orientation error of 1.57 ± 1.31°.

CONCLUSION

The presented robot shows exceptional compatibility with a wide range of patients and bore sizes while maintaining clinically significant accuracy. Future work will focus on the validations in dynamic liver environments.

IRE made easy: introducing the robotic grid system for multiple parallel needle insertion in irreversible electroporation treatment

PURPOSE

Accurate needle placement is crucial for successful tumor treatment using the irreversible electroporation (IRE) method. Multiple needles are inserted around the tumor, ideally in parallel, to achieve uniform electric field distribution. This paper presents a robot utilizing a grid system to enable multiple needles insertion while maintaining parallelism between them.

METHODS

The robotic system has two degrees of freedom, which allow for the adjustment of the grid system to accommodate targeting lesions in various positions. The robot's performance was evaluated by testing its accuracy across various configurations and target depth locations, as well as its ability to maintain the needle parallelism.

RESULTS

The robot has dimensions of ϕ 134 mm and a height of 46 mm, with a total weight of 295 g. The system accuracy test showed that the robot can precisely target points across different target depths and needle orientations, with an average error of 2.71 ± 0.68 mm. Moreover, multiple insertions at different grid locations reveal needle orientation deviations typically below 1 ∘ .

CONCLUSION

This study presented the design and validation of a robotic grid system. The robot is capable of maintaining insertion accuracy and needle parallelism during multiple needle insertions at various robot configurations. The robot showed promising results with limited needle deviation, making it suitable for IRE procedures.

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.

Omnidirectional Monolithic Marker for Intra-Operative MR-Based Positional Sensing in Closed MRI

We present a design of an inductively coupled radio frequency (ICRF) marker for magnetic resonance (MR)-based positional tracking, enabling the robust increase of tracking signal at all scanning orientations in quadrature-excited closed MR imaging (MRI). The marker employs three curved resonant circuits fully covering a cylindrical surface that encloses the signal source. Each resonant circuit is a planar spiral inductor with parallel plate capacitors fabricated monolithically on flexible printed circuit board (FPC) and bent to achieve the curved structure. Size of the constructed marker is Ø3-mm ×5 -mm with quality factor > 22, and its tracking performance was validated with 1.5 T MRI scanner. As result, the marker remains as a high positive contrast spot under 360° rotations in 3 axes. The marker can be accurately localized with a maximum error of 0.56 mm under a displacement of 56 mm from the isocenter, along with an inherent standard deviation of 0.1-mm. Accrediting to the high image contrast, the presented marker enables automatic and real-time tracking in 3D without dependency on its orientation with respect to the MRI scanner receive coil. In combination with its small form-factor, the presented marker would facilitate robust and wireless MR-based tracking for intervention and clinical diagnosis. This method targets applications that can involve rotational changes in all axes (X-Y-Z).

Editorial for the Special Issue on Flexible Sensors and Actuators for Biomedicine

Flexible sensors and actuators typically rely on functional materials with low Young's moduli or ultrathin geometries [...].

A systematic review of image-guided, surgical robot-assisted percutaneous puncture: Challenges and benefits

Percutaneous puncture is a common medical procedure that involves accessing an internal organ or tissue through the skin. Image guidance and surgical robots have been increasingly used to assist with percutaneous procedures, but the challenges and benefits of these technologies have not been thoroughly explored. The aims of this systematic review are to furnish an overview of the challenges and benefits of image-guided, surgical robot-assisted percutaneous puncture and to provide evidence on this approach. We searched several electronic databases for studies on image-guided, surgical robot-assisted percutaneous punctures published between January 2018 and December 2022. The final analysis refers to 53 studies in total. The results of this review suggest that image guidance and surgical robots can improve the accuracy and precision of percutaneous procedures, decrease radiation exposure to patients and medical personnel and lower the risk of complications. However, there are many challenges related to the use of these technologies, such as the integration of the robot and operating room, immature robotic perception, and deviation of needle insertion. In conclusion, image-guided, surgical robot-assisted percutaneous puncture offers many potential benefits, but further research is needed to fully understand the challenges and optimize the utilization of these technologies in clinical practice.

Robotics in Interventional Radiology: Review of Current and Future Applications

This review is a brief overview of the current status and the potential role of robotics in interventional radiology. Literature published in the last decades, with an emphasis on the last 5 years, was reviewed and the technical developments in robotics and navigational systems using CT-, MR- and US-image guidance were analyzed. Potential benefits and disadvantages of their current and future use were evaluated. The role of fusion imaging modalities and artificial intelligence was analyzed in both percutaneous and endovascular procedures. A few hundred articles describing results of single or several systems were included in our analysis.

State of the Art and Future Opportunities in MRI-Guided Robot-Assisted Surgery and Interventions

Magnetic resonance imaging (MRI) can provide high-quality 3-D visualization of target anatomy, surrounding tissue, and instrumentation, but there are significant challenges in harnessing it for effectively guiding interventional procedures. Challenges include the strong static magnetic field, rapidly switching magnetic field gradients, high-power radio frequency pulses, sensitivity to electrical noise, and constrained space to operate within the bore of the scanner. MRI has a number of advantages over other medical imaging modalities, including no ionizing radiation, excellent soft-tissue contrast that allows for visualization of tumors and other features that are not readily visible by other modalities, true 3-D imaging capabilities, including the ability to image arbitrary scan plane geometry or perform volumetric imaging, and capability for multimodality sensing, including diffusion, dynamic contrast, blood flow, blood oxygenation, temperature, and tracking of biomarkers. The use of robotic assistants within the MRI bore, alongside the patient during imaging, enables intraoperative MR imaging (iMRI) to guide a surgical intervention in a closed-loop fashion that can include tracking of tissue deformation and target motion, localization of instrumentation, and monitoring of therapy delivery. With the ever-expanding clinical use of MRI, MRI-compatible robotic systems have been heralded as a new approach to assist interventional procedures to allow physicians to treat patients more accurately and effectively. Deploying robotic systems inside the bore synergizes the visual capability of MRI and the manipulation capability of robotic assistance, resulting in a closed-loop surgery architecture. This article details the challenges and history of robotic systems intended to operate in an MRI environment and outlines promising clinical applications and associated state-of-the-art MRI-compatible robotic systems and technology for making this possible.

MRI-guided lumbar spinal injections with body-mounted robotic system: cadaver studies

INTRODUCTION

This paper reports the system integration and cadaveric assessment of a body-mounted robotic system for MRI-guided lumbar spine injections. The system is developed to enable MR-guided interventions in closed bore magnet and avoid problems due to patient movement during cannula guidance.

MATERIAL AND METHODS

The robot is comprised by a lightweight and compact structure so that it can be mounted directly onto the lower back of a patient using straps. Therefore, it can minimize the influence of patient movement by moving with the patient. The MR-Conditional robot is integrated with an image-guided surgical planning workstation. A dedicated clinical workflow is created for the robot-assisted procedure to improve the conventional freehand MRI-guided procedure.

RESULTS

Cadaver studies were performed with both freehand and robot-assisted approaches to validate the feasibility of the clinical workflow and to assess the positioning accuracy of the robotic system. The experiment results demonstrate that the root mean square (RMS) error of the target position to be 2.57 ± 1.09 mm and of the insertion angle to be 2.17 ± 0.89°.

CONCLUSION

The robot-assisted approach is able to provide more accurate and reproducible cannula placements than the freehand procedure, as well as to reduce the number of insertion attempts.

Soft robotic manipulator for intraoperative MRI-guided transoral laser microsurgery

Magnetic resonance (MR) imaging (MRI) provides compelling features for the guidance of interventional procedures, including high-contrast soft tissue imaging, detailed visualization of physiological changes, and thermometry. Laser-based tumor ablation stands to benefit greatly from MRI guidance because 3D resection margins alongside thermal distributions can be evaluated in real time to protect critical structures while ensuring adequate resection margins. However, few studies have investigated the use of projection-based lasers like those for transoral laser microsurgery, potentially because dexterous laser steering is required at the ablation site, raising substantial challenges in the confined MRI bore and its strong magnetic field. Here, we propose an MR-safe soft robotic system for MRI-guided transoral laser microsurgery. Owing to its miniature size (Ø12 × 100 mm), inherent compliance, and five degrees of freedom, the soft robot ensures zero electromagnetic interference with MRI and enables safe and dexterous operation within the confined oral and pharyngeal cavities. The laser manipulator is rapidly fabricated with hybrid soft and hard structures and is powered by microvolume (<0.004 milliter) fluid flow to enable laser steering with enhanced stiffness and lowered hysteresis. A learning-based controller accommodates the inherent nonlinear robot actuation, which was validated with laser path-following tests. Submillimeter laser steering accuracy was demonstrated with a mean error < 0.20 mm. MRI compatibility testing demonstrated zero observable image artifacts during robot operation. Ex vivo tissue ablation and a cadaveric head-and-neck trial were carried out under MRI, where we employed MR thermometry to monitor the tissue ablation margin and thermal diffusion intraoperatively.

Preliminary Evaluation of Hydraulic Needle Delivery System for Magnetic Resonance Imaging-Guided Prostate Biopsy Procedures

In clinical routine, the prostate biopsy procedure is performed with the guidance of transrectal ultrasound (TRUS) imaging to diagnose prostate cancer. However, the TRUS-guided prostate biopsy brings reliability concerns due to the lack of contrast difference between prostate tissue and lesions. In this study, a novel hydraulic needle delivery system that is designed for performing magnetic resonance imaging (MRI)-guided prostate biopsy procedure with transperineal approach is introduced. The feasibility of the overall system was evaluated through in vitro phantom experiments under an MRI guidance. The in vitro experiments performed using a certified prostate phantom (incorporating MRI visible lesions). MRI experiments showed that overall hydraulic biopsy needle delivery system has excellent MRI compatibility (signal to noise ratio (SNR) loss &lt; 3%), provides acceptable targeting accuracy (average 2.05±0.46 mm) and procedure time (average 40 min).

Robot-Assisted Image-Guided Interventions

Image guidance is a common methodology of minimally invasive procedures. Depending on the type of intervention, various imaging modalities are available. Common imaging modalities are computed tomography, magnetic resonance tomography, and ultrasound. Robotic systems have been developed to enable and improve the procedures using these imaging techniques. Spatial and technological constraints limit the development of versatile robotic systems. This paper offers a brief overview of the developments of robotic systems for image-guided interventions since 2015 and includes samples of our current research in this field.

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.

Fully Actuated Body-Mounted Robotic System for MRI-Guided Lower Back Pain Injections: Initial Phantom and Cadaver Studies

This paper reports the improved design, system integration, and initial experimental evaluation of a fully actuated body-mounted robotic system for real-time MRI-guided lower back pain injections. The 6-DOF robot is composed of a 4-DOF needle alignment module and a 2-DOF remotely actuated needle driver module, which together provide a fully actuated manipulator that can operate inside the scanner bore during imaging. The system minimizes the need to move the patient in and out of the scanner during a procedure, and thus may shorten the procedure time and streamline the clinical workflow. The robot is devised with a compact and lightweight structure that can be attached directly to the patient's lower back via straps. This approach minimizes the effect of patient motion by allowing the robot to move with the patient. The robot is integrated with an image-based surgical planning module. A dedicated clinical workflow is proposed for robot-assisted lower back pain injections under real-time MRI guidance. Targeting accuracy of the system was evaluated with a real-time MRI-guided phantom study, demonstrating the mean absolute errors (MAE) of the tip position to be 1.50±0.68mm and of the needle angle to be 1.56±0.93°. An initial cadaver study was performed to validate the feasibility of the clinical workflow, indicating the maximum error of the position to be less than 1.90mm and of the angle to be less than 3.14°.