"MRI Stealth" robot for prostate interventions

A magnetic resonance conditional robot for lumbar spinal injection: Development and preliminary validation

PURPOSE

This work presents the design and preliminary validation of a Magnetic Resonance (MR) conditional robot for lumbar injection for the treatment of lower back pain.

METHODS

This is a 4-degree-of-freedom (DOF) robot that is 200 × 230 × 130 mm3 in volume and has a mass of 0.8 kg. Its lightweight and compact features allow it to be directly affixed to patient's back, establishing a rigid connection, thus reducing positional errors caused by patient movements during treatment.

RESULTS

To validate the positioning accuracy of the needle by the robot, an electromagnetic (EM) tracking system and a needle with an EM sensor embedded in the tip were used for the free space evaluation with position accuracy of 0.88 ± 0.46 mm and phantom mock insertions using the Loop-X CBCT scanner with target position accuracy of 3.62 ± 0.92 mm.

CONCLUSION

Preliminary experiments demonstrated that the proposed robot showed improvements and benefits in its rotation range, flexible needle adjustment, and sensor protection compared with previous and existing systems, offering broader clinical applications.

Robotic systems in interventional oncology: a narrative review of the current status

Interventional oncology offers minimally invasive treatments for malignant tumors for curative and palliative purposes based on the percutaneous insertion of needles or catheters into the target location under image guidance. Robotic systems have been gaining increasing attention as tools that provide potential advantages for image-guided interventions. Among the robotic systems developed for intervention, those relevant to the oncology field are mainly those for guiding or driving the needles in non-vascular interventional procedures such as biopsy and tumor ablation. Needle-guiding robots support planning the needle path and align the needle robotically according to the planned trajectory, which is combined with subsequent manual needle insertion by the physician through the needle guide. Needle-driving robots can advance the needle robotically after determining its orientation. Although a wide variety of robotic systems have been developed, only a limited number of these systems have reached the clinical phase or commercialization thus far. The results of previous studies suggest that such interventional robots have the potential to increase the accuracy of needle placement, facilitate out-of-plane needle insertion, decrease the learning curve, and reduce radiation exposure. On the other hand, increased complexity and costs may be a concern when using robotic systems compared with conventional manual procedures. Further data should be collected to comprehensively assess the value of robotic systems in interventional oncology.

Preliminary evaluation for ultrasound-guided targeted prostate biopsy using a portable surgical robot: Ex vivo results

BACKGROUND

Robotic systems are increasingly used to enhance clinical outcomes in prostate intervention. To evaluate the clinical value of the proposed portable robot, the robot-assisted and robot-targeted punctures were validated experimentally.

METHOD

The robot registration utilising the electromagnetic tracker achieves coordinate transformation from the ultrasound (US) image to the robot. Subsequently, Transrectal ultrasound (TRUS)-guided phantom trials were conducted for robot-assisted, free-hand, and robot-targeted punctures.

RESULTS

The accuracy of robot registration was 0.95 mm, and the accuracy of robot-assisted, free-hand, and robot-targeted punctures was 2.38 ± 0.64 mm, 3.11 ± 0.72 mm, and 3.29 ± 0.83 mm sequentially.

CONCLUSION

The registration method has been successfully applied to robot-targeted puncture. Current results indicate that the accuracy of robot-targeted puncture is slightly inferior to that of manual operations. Moreover, in manual operation, robot-assisted puncture improves the accuracy of free-hand puncture. Accuracy superior to 3.5 mm demonstrates the clinical applicability of both robot-assisted and robot-targeted punctures.

Robotic Instruments Inside the MRI Bore: Key Concepts and Evolving Paradigms in Imaging-enhanced Cranial Neurosurgery

Intraoperative MRI has been increasingly used to robotically deliver electrodes and catheters into the human brain using a linear trajectory with great clinical success. Current cranial MR guided robotics do not allow for continuous real-time imaging during the procedure because most surgical instruments are not MR-conditional. MRI guided robotic cranial surgery can achieve its full potential if all the traditional advantages of robotics (such as tremor-filtering, precision motion scaling, etc.) can be incorporated with the neurosurgeon physically present in the MRI bore or working remotely through controlled robotic arms. The technological limitations of design optimization, choice of sensing, kinematic modeling, physical constraints, and real-time control had hampered early developments in this emerging field, but continued research and development in these areas over time has granted neurosurgeons far greater confidence in using cranial robotic techniques. This article elucidates the role of MR-guided robotic procedures using clinical devices like NeuroBlate and Clearpoint that have several thousands of cases operated in a "linear cranial trajectory" and planned clinical trials, such as LAANTERN for MR guided robotics in cranial neurosurgery using LITT and MR-guided putaminal delivery of AAV2 GDNF in Parkinson's disease. The next logical improvisation would be a steerable curvilinear trajectory in cranial robotics with added DOFs and distal tip dexterity to the neurosurgical tools. Similarly, the novel concept of robotic actuators that are powered, imaged, and controlled by the MRI itself is discussed in this article, with its potential for seamless cranial neurosurgery.

MR conditional prostate intervention systems and actuations review

Magnetic resonance imaging (MRI) has the ability to provide high-resolution images of soft tissues without the use of radiation. So much research has been focused on the development of actuators and robotic devices that can be used in the MRI environment so "real-time" images can be obtained during surgeries. With real-time guidance from MRI, robots can perform surgical procedures with high accuracy and through less invasive routes. This technique can also significantly reduce the operation time and simplify pre-surgical procedures. Therefore, research on robot-assisted MRI-guided prostate intervention has attracted a great deal of interest, and several successful clinical trials have been published in recent years, pointing to the great potential of this technology. However, the development of MRI-guided robots is still in the primary stage, and collaboration between researchers and commercial suppliers is still needed to improve such robot systems. This review presents an overview of MRI-guided prostate intervention devices and actuators. Additionally, the expected technical challenges and future advances in this field are discussed.

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.

Preliminary Study of a Modular MR-Compatible Robot for Image-Guided Insertion of Multiple Needles

Percutaneous needle-based interventions such as transperineal prostate brachytherapy require the accurate placement of multiple needles to treat cancerous lesions within the target organ. To guide needle placement, magnetic resonance imaging (MRI) offers excellent visualization of the target lesion without the need for ionizing radiation. To date, multi-needle insertion relies on a grid template, which limits the ability to steer individual needles. This work describes an MR-compatible robot designed for the sequential insertion of multiple non-parallel needles under MR guidance. The 6-DOF system is designed with an articulated arm to extend the reach of the robot. This strategy presents a novel approach enabling the robot to maneuver around existing needles while minimizing the footprint of the robot. Forward kinematics as well as optimization-based inverse kinematics are presented. The impact of the robot on image quality was tested for four sequences (T1w-TSE, T2w-TSE, THRIVE and EPI) on a 3T Philips Achieva system. Quantification of the signal-to-noise ratio showed a 46% signal loss in a gelatin phantom when the system was powered on but no further adverse effects when the robot was moving. Joint level testing showed a maximum error of 2.10 ± 0.72°s for revolute joints and 0.31 ± 0.60 mm for prismatic joints. The theoretical workspace spans the proposed clinical target surface of 10 x 10 cm. Lastly, the feasibility of multi-needle insertion was demonstrated with four needles inserted under real-time MR-guidance with no visible loss in image quality.

Design of a 6-DoF Parallel Robotic Platform for MRI Applications

In this work, the design, analysis, and characterization of a parallel robotic motion generation platform with 6-degrees of freedom (DoF) for magnetic resonance imaging (MRI) applications are presented. The motivation for the development of this robot is the need for a robotic platform able to produce accurate 6-DoF motion inside the MRI bore to serve as the ground truth for motion modeling; other applications include manipulation of interventional tools such as biopsy and ablation needles and ultrasound probes for therapy and neuromodulation under MRI guidance. The robot is comprised of six pneumatic cylinder actuators controlled via a robust sliding mode controller. Tracking experiments of the pneumatic actuator indicates that the system is able to achieve an average error of 0.69 ± 0.14 mm and 0.67 ± 0.40 mm for step signal tracking and sinusoidal signal tracking, respectively. To demonstrate the feasibility and potential of using the proposed robot for minimally invasive procedures, a phantom experiment was performed in the benchtop environment, which showed a mean positional error of 1.20 ± 0.43 mm and a mean orientational error of 1.09 ± 0.57°, respectively. Experiments conducted in a 3T whole body human MRI scanner indicate that the robot is MRI compatible and capable of achieving positional error of 1.68 ± 0.31 mm and orientational error of 1.51 ± 0.32° inside the scanner, respectively. This study demonstrates the potential of this device to enable accurate 6-DoF motions in the MRI environment.

A review of the research progress of interventional medical equipment and methods for prostate cancer

BACKGROUND

Prostate cancer is a common disease in men and has a relatively high mortality rate. However, the interventional medical equipment used for prostate biopsy and brachytherapy has always been a social concern.

METHODS

To understand interventional medical equipment for prostate cancer, the structure of manual, semi-automatic and automatic medical equipment were considered as the mainline, while the corresponding research on these structures were the auxiliary lines. The characteristics and corresponding research status have been discussed.

RESULTS

Interventional medical equipment for prostate cancer with different degrees of automation and its characteristics were determined, and the imaging principles and characteristics of computed tomography, transrectal ultrasound and magnetic resonance imaging have been briefly described.

CONCLUSION

Certain feasible research suggestions have been proposed for future development from the perspective of structure, accuracy and safety. These include flexible and compact robot structures, high-precision image recognition and guidance, accurate dose planning and monitoring, real-time imaging monitoring without delay, high-precision needle insertion strategy, master-slave control, virtual reality and remote control.

A body-mounted device for MRI-guided spinal therapy

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with no cure and limited treatment options. Recent studies have shown that delivering cellular therapeutics to the ventral horn of the spinal cord can effectively halt neurodegeneration associated with ALS in small animal models.

METHODS

We developed a robotic system that assists with MRI-guided percutaneous injections to the spinal cord. The needle positioning robot consists of two linear axes with motorised translational sleds for two-degree-of-freedom (2-DOF) needle translation and a radial template for 2-DOF discrete rotation.

RESULTS

The robot's targeting capability, evaluated using phantom models and swine cadavers, showed mean targeting errors of 0.48 and 2.84 mm, respectively. The duration of the targeting procedure is approximately 60 min, with an extra 10 min for each additional injection.

CONCLUSIONS

The presented robot does not affect imaging quality during MRI-guided procedures, and it enables a simplified workflow for MRI-guided spinal therapy.

Soft electromagnetic actuators

Rigid electromagnetic actuators serve our society in a myriad of ways for more than 200 years. However, their bulky nature restricts close collaboration with humans. Here, we introduce soft electromagnetic actuators (SEMAs) by replacing solid metal coils with liquid-metal channels embedded in elastomeric shells. We demonstrate human-friendly, simple, stretchable, fast, durable, and programmable centimeter-scale SEMAs that drive a soft shark, interact with everyday objects, or rapidly mix a dye with water. A multicoil flower SEMA with individually controlled petals blooms or closes within tens of milliseconds, and a cubic SEMA performs programmed, arbitrary motion sequences. We develop a numerical model supporting design and opening potential routes toward miniaturization, reduction of power consumption, and increase in mechanical efficiency. SEMAs are electrically controlled shape-morphing systems that are potentially empowering future applications from soft grippers to minimally invasive medicine.

Demonstration and Experimental Validation of Plastic-Encased Resonant Ultrasonic Piezoelectric Actuator for Magnetic Resonance Imaging-Guided Surgical Robots

Intra-operative medical imaging based on magnetic resonance imaging (MRI) coupled with robotic manipulation of surgical instruments enables precise feedback-driven procedures. Electrically powered nonferromagnetic motors based on piezoelectric elements have shown to be well suited for MRI robots. However, even avoiding ferrous materials, the high metal content on commercially available motors still cause distortions to the magnetic fields. We construct semicustom piezoelectric actuators wherein the quantity of conductive material is minimized and demonstrate that the distortion issues can be partly addressed through substituting several of these components for plastic equivalents, while maintaining motor functionality. Distortion was measured by assessing the root-mean-squared (RMS) change in position of 49 centroid points in a 12.5 mm square grid of a gelatin-filled phantom. The metal motor caused a distortion of up to 4.91 mm versus 0.55 mm for the plastic motor. An additional signal-to-noise-ratio (SNR) drop between motor off and motor spinning of approximately 20% was not statistically different for metal versus plastic (p = 0.36).

NITINOL-based actuator for device control even in high-field MRI environment

Background

The magnetic resonance imaging (MRI) environment with its high-strength magnetic fields requires specialized and sometimes sophisticated solutions for otherwise simple problems. One of these problems is MR-compatible actuator mechanisms that transfer a signal into an action.

Purpose

Normal actuators are based on a magnetic effect (eg, relays) and will typically not work in magnetic fields exceeding 1000 G, eg, inside the bore of an MR scanner. To enable the use of clinical devices inside the MRI, eg, for interventional procedures, there is a need for fully compatible actuators.

Patients and methods

Various actuators were compared for the purpose as a simple on-off switch within an MRI. NITNOL wire as an actuator showed the highest potential because of its simplicity and reliability. We tested the possible force achieved by the NITINOL wire related to the respective energy consumption, to provide a travel range of 2 mm.

Results

Compared to other actuators, the NITNOL wire is cheaper and requires less space. In the switching process however, there is a delay due to the time required for the heating of the wire up to the transformation temperature. The NITINOL switch shows a reliable behavior with regard to the generated force and the switching path over the entire measurement. Significant artifacts, caused by the NITNOL wire could not be detected in the MRI.

Conclusion

NITINOL wires can be repeatedly used, are relatively easy to implement and could be an economic alternative to other more complicated actuator technologies.

Lung and Abdominal Biopsies in the Age of Precision Medicine

Image-guided percutaneous needle biopsies (PNBs) are one of the most common procedures performed in radiology departments today. Rapid developments in precision medicine, which identifies molecular and genomic biomarkers in cancers, have ushered a new paradigm of oncologic workup and treatment. PNB has conventionally been used to establish a benign or malignant nature of a lesion during initial diagnosis or in suspected metastatic or recurrent disease. However, increasing amounts of tissue are being required to meet the demands of molecular pathologic analysis, which are now being sought at multiple time points during the course of the disease to guide targeted therapy. As primary providers of biopsy, radiologists must be proactive in these developments to improve diagnostic yield and tissue acquisition in PNB. Herein, we discuss the important and expanding role of PNB in the age of precision medicine and review the technical considerations of percutaneous lung and intra-abdominal biopsy. Finally, we examine promising state-of-the-art techniques in PNB that may safely increase tissue acquisition for optimal molecular pathologic analysis.

Review of Robotic Needle Guide Systems for Percutaneous Intervention

Numerous research groups in the past have designed and developed robotic needle guide systems that improve the targeting accuracy and precision by either providing a physical guidance for manual insertion or enabling a complete automated intervention. Here we review systems that have been reported in the last 11 years and limited to straight line needle interventions. Most systems fall under the category of image guided systems as they either use magnetic resonance image, computed tomography, ultrasound or a combination of these modalities for real time image feedback of the intervention path being followed. Actuation and control technology along with materials used for construction are the main aspects that differentiate these systems from each other and have been reviewed here. Image compatibility test details and results are also reviewed as they are used to ensure proper functioning of these systems under the respective imaging environments. We have also reviewed needle guide systems which either don't use any image feedback or have not reported any but provide physical guidance. Throughout this paper, we provide a comprehensive review of the technological aspects and trends in the field of robotic, straight line, needle guide intervention systems.

DEMONSTRATION AND EXPERIMENTAL VALIDATION OF PLASTIC-ENCASED RESONANT ULTRASONIC PIEZOELECTRIC ACTUATOR FOR MRI-GUIDED SURGICAL ROBOTS

Intra-operative medical imaging based on magnetic resonance imaging (MRI) coupled with robotic manipulation of surgical instruments enables precise feedback-driven procedures. Electrically powered non-ferromagnetic motors based on piezoelectric elements have shown to be well suited for MRI robots. However, even avoiding ferrous materials, the high metal content on commercially available motors still cause distortions to the magnetic fields. We construct semi-custom piezoelectric actuators wherein the quantity of conductive material is minimized and demonstrate that the distortion issues can be partly addressed through substituting several of these components for plastic equivalents, while maintaining motor functionality. Distortion was measured by assessing the RMS change in position of 49 centroid points in a 12.5mm square grid of a gelatin-filled phantom. The metal motor caused a distortion of up to 4.91mm versus 0.55mm for the plastic motor. An additional SNR drop between motor off and motor spinning of approximately 20% was not statistically different for metal versus plastic (p=0.36).

System Integration and Preliminary Clinical Evaluation of a Robotic System for MRI-Guided Transperineal Prostate Biopsy

This paper presents the development, preclinical evaluation, and preliminary clinical study of a robotic system for targeted transperineal prostate biopsy under direct interventional magnetic resonance imaging (MRI) guidance. The clinically integrated robotic system is developed based on a modular design approach, comprised of surgical navigation application, robot control software, MRI robot controller hardware, and robotic needle placement manipulator. The system provides enabling technologies for MRI-guided procedures. It can be easily transported and setup for supporting the clinical workflow of interventional procedures, and the system is readily extensible and reconfigurable to other clinical applications. Preclinical evaluation of the system is performed with phantom studies in a 3 Tesla MRI scanner, rehearsing the proposed clinical workflow, and demonstrating an in-plane targeting error of 1.5mm. The robotic system has been approved by the institutional review board (IRB) for clinical trials. A preliminary clinical study is conducted with the patient consent, demonstrating the targeting errors at two biopsy target sites to be 4.0mm and 3.7mm, which is sufficient to target a clinically significant tumor foci. First-in-human trials to evaluate the system's effectiveness and accuracy for MR image-guide prostate biopsy are underway.

A study on observed ultrasonic motor-induced magnetic resonance imaging (MRI) artifacts

Background

The safe performance of magnetic resonance imaging (MRI)-guided robot-assisted interventions requires full control and high precision of assistive devices. Because many currently available tools are not MRI-compatible, the characterization of existing tools and development of new ones are necessary. The purpose of this research is to identify and minimize the image artifacts generated by a USM in MR images.

Methods

The behavior of an ultrasonic motor (USM), the most common MRI-safe actuator, in a high-field scanner was investigated. The motor was located in three orientations with respect to the bore axis with the power on or off. The induced image artifacts were compared across four sequences. Three artifact reduction methods (employing ultrashort sequences, slice thickness reductions, and bandwidth increments) were tested.

Results

Signal voids, pileups, and geometric distortions were observed when the motor was off. The artifact size was minimal when the motor shaft was aligned with the bore axis. In addition to the above artifacts, zipper and motion artifacts were noted when the motor was running, and these artifacts increased with increasing motor speed. Increasing the bandwidth slightly reduced the artifacts. However, decreasing the slice thickness from 5 mm to 3 mm and from 5 mm to 1 mm reduced artifact size from 30% to 40% and from 60% to 75%, respectively.

Conclusion

The image artifacts were due to the non-homogenous nature of the static and gradient fields caused by the motor structure. The operating motor interferes with the RF field, causing zipper and motion artifacts.

Robotically assisted long bone biopsy under MRI: cadaver study results

RATIONALE AND OBJECTIVES

We have designed and constructed an MR-safe robot made entirely of nonmetallic components with pneumatic actuators and optical encoders. The robot was developed to enable bone biopsies to be performed under magnetic resonance imaging (MRI) guidance in pediatric patients. The purpose of this study was to show the feasibility of using the robot for biopsy of the femur and tibia in a cadaver leg. Our long-term goal is to eliminate radiation exposure during bone biopsy procedures and provide more timely and accurate diagnosis for children with bone cancers and bone infections.

METHODS

The MR-safe robot was mounted on the MRI table. A cadaver leg was procured from an anatomy supply house and placed on the MRI table. All required hospital precautions for infection control were taken. A total of 10 biopsy targets were sampled using MRI guidance: five from the femur and five from the tibia. A handheld, commercially available battery-powered bone drill was used to facilitate drilling through the cortex. After the study, the leg was scanned with CT to better visualize and document the bone biopsy sites. Both the MRI and CT images were used to analyze the results.

RESULTS

All of the targets were successfully reached with an average targeting accuracy of 1.43 mm. A workflow analysis showed the average time for the first biopsy was 41 min including robot setup time and 22 min for each additional biopsy including the time for the repeat MRI scan used to confirm accurate targeting. The robot was shown to be MRI transparent, as no image quality degradation due to the use of the robot was detected.

CONCLUSION

The results showed the feasibility of using an MR-safe robotic system to assist the interventional radiologist in performing precision bone biopsy under MRI guidance. Future work will include developing an MR-safe drill, improving the mounting of the robot and fixation of the leg, and moving toward first in child clinical trials.

Fast 3-T MR-guided transrectal prostate biopsy using an in-room tablet device for needle guide alignment: a feasibility study

OBJECTIVES

To assess the feasibility of adding a tablet device inside the scanner room to assist needle-guide alignment during magnetic resonance (MR)-guided transrectal prostate biopsy.

METHODS

Twenty patients with one cancer-suspicious region (CSR) with PI-RADS score ≥ 4 on diagnostic multiparametric MRI were prospectively enrolled. Two orthogonal scan planes of an MR fluoroscopy sequence (~3 images/s) were aligned to the CSR and needle-guide pivoting point. Targeting was achieved by manipulating the needle-guide under MR fluoroscopy feedback on the in-room tablet device. Technical feasibility and targeting success were assessed. Complications and biopsy procedure times were also recorded.

RESULTS

Needle-guide alignment with the in-room tablet device was technically successful in all patients and allowed sampling after a single alignment step in 19/20 (95%) CSRs (median size 14 mm, range: 4-45). Biopsy cores contained cancer in 18/20 patients. There were no per-procedural or post-biopsy complications. Using the tablet device, the mean time to first biopsy was 5.8 ± 1.0 min and the mean total procedure time was 23.7 ± 4.1 min.

CONCLUSIONS

Use of an in-room tablet device to assist needle-guide alignment was feasible and safe during MR-guided transrectal prostate biopsy. Initial experience indicates potential for procedure time reduction.

KEY POINTS

• Performing MR-guided prostate biopsy using an in-room tablet device is feasible. • CSRs could be sampled after a single alignment step in 19/20 patients. • The mean procedure time for biopsy with the tablet device was 23.7 min.

SpinoBot: An MRI-Guided Needle Positioning System for Spinal Cellular Therapeutics

The neurodegenerative disease amyotrophic lateral sclerosis (ALS) results in the death of motor neurons in voluntary muscles. There are no cures for ALS and few available treatments. In studies with small animal models, injection of cellular therapeutics into the anterior horn of the spinal cord has been shown to inhibit the progression of ALS. It was hypothesized that spinal injection could be made faster and less invasive with the aid of a robot. The robotic system presented-SpinoBot-uses MRI guidance to position a needle for percutaneous injection into the spinal cord. With four degrees of freedom (DOF) provided by two translation stages and two rotational axes, SpinoBot proved capable of advanced targeting with a mean error of 1.12 mm and standard deviation of 0.97 mm in bench tests, and a mean error of 2.2 mm and standard deviation of 0.85 mm in swine cadaver tests. SpinoBot has shown less than 3% signal-to-noise ratio reduction in 3T MR imaging quality, demonstrating its compliance to the MRI environment. With the aid of SpinoBot, the length of the percutaneous injection procedure is reduced to less than 60 min with 10 min for each additional insertion. Although SpinoBot is designed for ALS treatment, it could potentially be used for other procedures that require precise access to the spine.

MR Safe Robot Assisted Needle Access of the Brain: Preclinical Study

We report the results of preclinical experiments for direct MRI-guided needle interventions in the brain. An MR Safe robot was incorporated into an intraoperative MRI system. Deep regions of the brain simulated in a cranial mockup were targeted with a needle under robotic assistance. The 3D accuracy of in-scanner targeting at an average depth of 95[Formula: see text]mm was 1.55[Formula: see text]mm, with no manual corrections.

Robotics in MRI-Guided Interventions

Robots have been found to be a useful tool in magnetic resonance imaging (MRI)-guided intervention. The utility of robots in MRI-guided therapy ranges from aid for precision targeting to high-dexterity surgical tools to improve or even enable new MRI-guided therapy options. The objective of this article is to review the technical aspects of robotics in MRI-guided interventions, highlight the role of MRI robots in prostate interventions, and finally discuss the future contribution of emerging robotics technology useful in MRI-guided intervention.

Techniques for Interventional MRI Guidance in Closed-Bore Systems

Efficient image guidance is the basis for minimally invasive interventions. In comparison with X-ray, computed tomography (CT), or ultrasound imaging, magnetic resonance imaging (MRI) provides the best soft tissue contrast without ionizing radiation and is therefore predestined for procedural control. But MRI is also characterized by spatial constraints, electromagnetic interactions, long imaging times, and resulting workflow issues. Although many technical requirements have been met over the years-most notably magnetic resonance (MR) compatibility of tools, interventional pulse sequences, and powerful processing hardware and software-there is still a large variety of stand-alone devices and systems for specific procedures only.Stereotactic guidance with the table outside the magnet is common and relies on proper registration of the guiding grids or manipulators to the MR images. Instrument tracking, often by optical sensing, can be added to provide the physicians with proper eye-hand coordination during their navigated approach. Only in very short wide-bore systems, needles can be advanced at the extended arm under near real-time imaging. In standard magnets, control and workflow may be improved by remote operation using robotic or manual driving elements.This work highlights a number of devices and techniques for different interventional settings with a focus on percutaneous, interstitial procedures in different organ regions. The goal is to identify technical and procedural elements that might be relevant for interventional guidance in a broader context, independent of the clinical application given here. Key challenges remain the seamless integration into the interventional workflow, safe clinical translation, and proper cost effectiveness.

The MIRIAM Robot: A Novel Robotic System for MR-Guided Needle Insertion in the Prostate

Early prostate cancer detection and treatment are of major importance to reduce mortality rate. magnetic resonance (MR) imaging provides images of the prostate where an early stage lesion can be visualized. The use of robotic systems for MR-guided interventions in the prostate allows us to improve the clinical outcomes of procedures such as biopsy and brachytherapy. This work presents a novel MR-conditional robot for prostate interventions. The minimally invasive robotics in an magnetic resonance imaging environment (MIRIAM) robot has 9 degrees-of-freedom (DoF) used to steer and fire a biopsy needle. The needle guide is positioned against the perineum by a 5 DoF parallel robot driven by piezoelectric motors. A 4 DoF needle driver inserts, rotates and fires the needle during the procedure. Piezoelectric motors are used to insert and rotate the needle, while pneumatic actuation is used to fire the needle. The MR-conditional design of the robot and the needle insertion controller are presented. MR compatibility tests using T2 imaging protocol are performed showing a SNR reduction of 25% when the robot is operational within the MR scanner. Experiments inserting a biopsy needle toward a physical target resulted in an average targeting error of 1.84[Formula: see text]mm. Our study presents a novel MR-conditional robot and demonstrated the ability to perform MR-guided needle-based interventions in soft-tissue phantoms. Moreover, the image distortion analysis indicates that no visible image deterioration is induced by the robot.

A new 4-DOF parallel robot for MRI-guided percutaneous interventions: Kinematic analysis

In this paper, we present the concept of a novel 4-DOF parallel robot for MRI-guided percutaneous interventions. This system belongs to the class of patient-mounted robots, with two parallel circular stages along which two actuating joints move. As a first step, we present the concept of the robot and its kinematic analysis. This robot has the potential of increased rigidity and reduced inertial effect compared to its predecessor. It also minimizes the number of moving components, which enhances safety during the robot's operation.

Safety and Feasibility of Direct Magnetic Resonance Imaging-guided Transperineal Prostate Biopsy Using a Novel Magnetic Resonance Imaging-safe Robotic Device

OBJECTIVE

To evaluate safety and feasibility in a first-in-human trial of a direct magnetic resonance imaging (MRI)-guided prostate biopsy using a novel robotic device.

METHODS

MrBot is an MRI-safe robotic device constructed entirely with nonconductive, nonmetallic, and nonmagnetic materials and developed by our group. A safety and feasibility clinical trial was designed to assess the safety and feasibility of a direct MRI-guided biopsy with MrBot and to determine its targeting accuracy. Men with elevated prostate-specific antigen levels, prior negative prostate biopsies, and cancer-suspicious regions (CSRs) on MRI were enrolled in the study. Biopsies targeting CSRs, in addition to sextant locations, were performed.

RESULTS

Five men underwent biopsy with MrBot. Two men required Foley catheter insertion after the procedure, with no other complications or adverse events. Even though this was not a study designed to detect prostate cancer, biopsies confirmed the presence of a clinically significant cancer in 2 patients. On a total of 30 biopsy sites, the robot achieved an MRI-based targeting accuracy of 2.55 mm and a precision of 1.59 mm normal to the needle, with no trajectory corrections and no unsuccessful attempts to target a site.

CONCLUSION

Robot-assisted MRI-guided prostate biopsy appears safe and feasible. This study confirms that a clinically significant prostate cancer (≥5-mm radius, 0.5 cm³) depicted in MRI may be accurately targeted. Direct confirmation of needle placement in the CSR may present an advantage over fusion-based technology and gives more confidence in a negative biopsy result. Additional study is warranted to evaluate the efficacy of this approach.

Ultrasonic motor-induced geometric distortions in magnetic resonance images

Ultrasonic motors (USMs) are common actuators that can be safely used in the magnetic resonance imaging (MRI) environment. However, lack of MRI compatibility results in issues such as image distortion. This fact led researchers to shift focus from USMs to pneumatic and hydraulic actuators in development of surgical robots. The aim is to quantify and compensate the geometric distortion of MR images as generated by the presence of USMs. An ultrasonic motor was positioned in three orientations with respect to the bore axis. The induced distortions were compared across four image sequences. To reduce the distortions, three artifact reduction methods were employed. Geometric distortion is the only artifact in image slices farther from the motor. The various motor orientations lead to different distortions, with the lowest distortion for the z orientation. The maximum measured distortion of ten pixels occurred. This maximal distortion is equal to a 1-cm displacement of the displayed points relative to their actual locations and it is beyond the acceptable level for medical display standards. Bandwidth reduction reduced the distortion, with a 50% reduction for a doubled bandwidth. In conclusion, USMs can be preferred alternative because accurate targeting of pathologies can occur in free distorted images.

Manipulator-driven selection of semi-active MR-visible markers

BACKGROUND

A method for the identification of semi-active fiducial magnetic resonance (MR) markers is presented based on selectively optically tuning and detuning them.

METHODS

Four inductively coupled solenoid coils with photoresistors were connected to light sources. A microcontroller timed the optical tuning/detuning of coils and image collection. The markers were tested on an MR manipulator linking the microcontroller to the manipulator control to visibly select the marker subset according to the actuated joint.

RESULTS

In closed-loop control, the average and maximum were 0.76° ± 0.41° and 1.18° errors for a rotational joint, and 0.87 mm ± 0.26 mm and 1.13 mm for the prismatic joint.

CONCLUSIONS

This technique is suitable for MR-compatible actuated devices that use semi-active MR-compatible markers.

Multi-Imager Compatible, MR Safe, Remote Center of Motion Needle-Guide Robot

We report the development of a new robotic system for direct image-guided interventions (DIGI; images acquired at the time of the intervention). The manipulator uses our previously reported pneumatic step motors and is entirely made of electrically nonconductive, nonmetallic, and nonmagnetic materials. It orients a needle-guide with two degrees of freedom (DoF) about a fulcrum point located below the guide using an innovative remote center of motion parallelogram type mechanism. The depth of manual needle insertion is preset with a third DoF, located remotely of the manipulator. Special consideration was given to the kinematic accuracy and the structural stiffness. The manipulator includes registration markers for image-to-robot registration. Based on the images, it may guide needles, drills, or other slender instruments to a target (OD < 10 mm). Comprehensive preclinical tests were performed. The manipulator is MR safe (ASTM F2503-13). Electromagnetic compatibility (EMC) testing (IEC 60601-1-2) of the system shows that it does not conduct or radiate EM emissions. The change in the signal to noise ratio of the MRI due to the presence and motion of the robot in the scanner is below 1%. The structural stiffness at the needle-guide is 33 N/mm. The angular accuracy and precision of the manipulator itself are 0.177° and 0.077°. MRI-guided targeting accuracy and precision in vitro were 1.71 mm and 0.51 mm, at an average target depth of ∼38 mm, with no adjustments. The system may be suitable for DIGI where [mm] accuracy lateral to the needle (2D) or [mm] in 3D is acceptable. The system is also multi-imager compatible and could be used with other imaging modalities.

Signal-to-noise ratio evaluation of magnetic resonance images in the presence of an ultrasonic motor

Background

Safe robot-assisted intervention using magnetic resonance imaging (MRI) guidance requires the precise control of assistive devices, and most currently available tools are rarely MRI-compatible. To obtain high precision, it is necessary to characterize and develop existing MRI-safe actuators for use in a high magnetic field (≥3 T). Although an ultrasonic motor (USM) is considered to be an MRI-safe actuator, and can be used in the vicinity of a high field scanner, its presence interferes with MR images. Although an MR image provides valuable information regarding the pathology of a patient’s body, noise, generally of a granular type, decreases the quality of the image and jeopardizes the true evaluation of any existing pathological issues. An eddy current induced in the conductor material of the motor structure can be a source of noise when the motor is close to the isocenter of the image. We aimed to assess the effects of a USM on the signal-to-noise ratio (SNR) of MR images in a 3-T scanner. The SNR was compared for four image sequences in transverse directions for three orientations of the motor (x, y, and z) when the motor was in the “off” state. The SNR was evaluated to assess three artifact reduction methods used to minimize the motor-induced artifacts.

Results

The SNR had a range of 5–10 dB for slices close to the motor in the x and y orientations, and increased to 15–20 dB for slices far from the motor. Averaging the SNR for slices in all cases gave an SNR loss of about 10 dB. The maximum SNR was measured in the z orientation. In this case, the SNR loss was almost the same as that of other motor orientations, approximately 10 dB, but with a higher range, approximately 20–40 dB.

Conclusions

The selection of certain scanning parameters is necessary for reducing motor-generated artifacts. These parameters include slice selection and bandwidth. In developing any MRI-compatible assisted device actuated by a USM, this study recommends the use of an approximately 3-mm slice thickness with minimum bandwidth to achieve optimized SNR values when a USM is operating close to (within approximately 40 mm) the region being imaged. The SNR can be further enhanced by increasing the number of signal averages, but this is achieved only at the cost of increased scan duration.

MR Safe Robot, FDA Clearance, Safety and Feasibility Prostate Biopsy Clinical Trial

Compatibility of mechatronic devices with the MR environment has been a very challenging engineering task. After over a decade of developments, we report the successful translation to clinical trials of our MR Safe robot technology. MrBot is a 6-degree-of-freedom, pneumatically actuated robot for transperineal prostate percutaneous access, built exclusively of electrically nonconductive and nonmagnetic materials. Its extensive pre-clinical tests have been previously reported. Here, we present the latest technology developments, an overview of the regulatory protocols, and technically related results of the clinical trial. The FDA has approved the MrBot for the biopsy trial, which was successfully performed in 5 patients. With no trajectory corrections, and no unsuccessful attempts to target a site, the robot achieved an MRI based needle targeting accuracy of 2.55 mm. To the best of our knowledge, this is the first robot approved by the FDA for the MR environment. The results confirm that it is possible to perform safe and accurate robotic manipulation in the MRI scanner, and the development of MR Safe robots is no longer a daunting technical challenge.

The utilization of magnetic resonance imaging in the operating room

Online image guidance in the operating room using ultrasound imaging led to the resurgence of prostate brachytherapy in the 1980s. Here we describe the evolution of integrating MRI technology in the brachytherapy suite or operating room. Given the complexity, cost, and inherent safety issues associated with MRI system integration, first steps focused on the computational integration of images rather than systems. This approach has broad appeal given minimal infrastructure costs and efficiencies comparable with standard care workflows. However, many concerns remain regarding accuracy of registration through the course of a brachytherapy procedure. In selected academic institutions, MRI systems have been integrated in or near the brachytherapy suite in varied configurations to improve the precision and quality of treatments. Navigation toolsets specifically adapted to prostate brachytherapy are in development and are reviewed.

Towards human-controlled, real-time shape sensing based flexible needle steering for MRI-guided percutaneous therapies

BACKGROUND

Accurate needle placement into soft tissue is essential to percutaneous prostate cancer diagnosis and treatment procedures.

METHODS

This paper discusses the steering of a 20 gauge (G) FBG-integrated needle with three sets of Fiber Bragg Grating (FBG) sensors. A fourth-order polynomial shape reconstruction method is introduced and compared with previous approaches. To control the needle, a bicycle model based navigation method is developed to provide visual guidance lines for clinicians. A real-time model updating method is proposed for needle steering inside inhomogeneous tissue. A series of experiments were performed to evaluate the proposed needle shape reconstruction, visual guidance and real-time model updating methods.

RESULTS

Targeting experiments were performed in soft plastic phantoms and in vitro tissues with insertion depths ranging between 90 and 120 mm. Average targeting errors calculated based upon the acquired camera images were 0.40 ± 0.35 mm in homogeneous plastic phantoms, 0.61 ± 0.45 mm in multilayer plastic phantoms and 0.69 ± 0.25 mm in ex vivo tissue.

CONCLUSIONS

Results endorse the feasibility and accuracy of the needle shape reconstruction and visual guidance methods developed in this work. The approach implemented for the multilayer phantom study could facilitate accurate needle placement efforts in real inhomogeneous tissues. Copyright © 2016 John Wiley & Sons, Ltd.

Master device for teleoperated needle insertion-type interventional robotic system

This paper proposes a new master device for teleoperated needle insertion-type interventional robotic system. The 5-DOF master device is optimally designed based on the newly defined interventional procedures and the physicians' requirements. It comprises a 2-DOF rotational mechanism for adjustment of needle orientation, a 2-DOF translational mechanism for fine-tuning of needle entry point, and a handle assembly. The handle assembly includes a 1-DOF translational mechanism for needle insertion and buttons for operation mode selection. The passive actuation modules of the rotational mechanism and the active actuation modules of the translational mechanism are controlled appropriately for the selected mode according to the procedure phase. The needle insertion mechanism also warns the user by vibrating the shaft when the needle reaches the dangerous region.

Reduced dose to urethra and rectum with the use of variable needle spacing in prostate brachytherapy: a potential role for robotic technology

Purpose

Several robotic delivery systems for prostate brachytherapy are under development or in pre-clinical testing. One of the features of robotic brachytherapy is the ability to vary spacing of needles at non-fixed intervals. This feature may play an important role in prostate brachytherapy, which is traditionally template-based with fixed needle spacing of 0.5 cm. We sought to quantify potential reductions in the dose to urethra and rectum by utilizing variable needle spacing, as compared to fixed needle spacing.

Material and methods

Transrectal ultrasound images from 10 patients were used by 3 experienced planners to create 120 treatment plans. Each planner created 4 plan variations per patient with respect to needle positions: ¹²⁵I fixed spacing, ¹²⁵I variable spacing, ¹⁰³Pd fixed spacing, and ¹⁰³Pd variable spacing. The primary planning objective was to achieve a prostate V₁₀₀ of 100% while minimizing dose to urethra and rectum.

Results

All plans met the objective of achieving prostate V₁₀₀ of 100%. Combined results for all plans show statistically significant improvements in all assessed dosimetric variables for urethra (U_max, U_mean, D₃₀, D₅) and rectum (R_max, R_mean, R_V100) when using variable spacing. The dose reductions for mean and maximum urethra dose using variable spacing had p values of 0.011 and 0.024 with ¹⁰³Pd, and 0.007 and 0.029 with ¹²⁵I plans. Similarly dose reductions for mean and maximum rectal dose using variable spacing had p values of 0.007 and 0.052 with ¹⁰³Pd, and 0.012 and 0.037 with ¹²⁵I plans.

Conclusions

The variable needle spacing achievable by the use of robotics in prostate brachytherapy allows for reductions in both urethral and rectal planned doses while maintaining prostate dose coverage. Such dosimetric advantages have the potential in translating to significant clinical benefits with the use of robotic brachytherapy.

Piezoelectrically Actuated Robotic System for MRI-Guided Prostate Percutaneous Therapy

This paper presents a fully-actuated robotic system for percutaneous prostate therapy under continuously acquired live magnetic resonance imaging (MRI) guidance. The system is composed of modular hardware and software to support the surgical workflow of intra-operative MRI-guided surgical procedures. We present the development of a 6-degree-of-freedom (DOF) needle placement robot for transperineal prostate interventions. The robot consists of a 3-DOF needle driver module and a 3-DOF Cartesian motion module. The needle driver provides needle cannula translation and rotation (2-DOF) and stylet translation (1-DOF). A custom robot controller consisting of multiple piezoelectric motor drivers provides precision closed-loop control of piezoelectric motors and enables simultaneous robot motion and MR imaging. The developed modular robot control interface software performs image-based registration, kinematics calculation, and exchanges robot commands and coordinates between the navigation software and the robot controller with a new implementation of the open network communication protocol OpenIGTLink. Comprehensive compatibility of the robot is evaluated inside a 3-Tesla MRI scanner using standard imaging sequences and the signal-to-noise ratio (SNR) loss is limited to 15%. The image deterioration due to the present and motion of robot demonstrates unobservable image interference. Twenty-five targeted needle placements inside gelatin phantoms utilizing an 18-gauge ceramic needle demonstrated 0.87 mm root mean square (RMS) error in 3D Euclidean distance based on MRI volume segmentation of the image-guided robotic needle placement procedure.

The System Design and Evaluation of a 7-DOF Image-Guided Venipuncture Robot

Accessing the venous bloodstream to deliver fluids or obtain a blood sample is the most common clinical routine practiced in the U.S. Practitioners continue to rely on manual venipuncture techniques, but success rates are heavily dependent on clinician skill and patient physiology. In the U.S., failure rates can be as high as 50% in difficult patients, making venipuncture the leading cause of medical injury. To improve the rate of first-stick success, we have developed a portable autonomous venipuncture device that robotically servos a needle into a suitable vein under image guidance. The device operates in real time, combining near-infrared and ultra-sound imaging, image analysis, and a 7-degree-of-freedom (DOF) robotic system to perform the venipuncture. The robot consists of a 3-DOF gantry to image the patient's peripheral forearm veins and a miniaturized 4-DOF serial arm to guide the cannula into the selected vein under closed-loop control. In this paper, we present the system architecture of the robot and evaluate the accuracy and precision through tracking, free-space positioning, and in vitro phantom cannulation experiments. The results demonstrate sub-millimeter accuracy throughout the operating workspace of the manipulator and a high rate of success when cannulating phantom veins in a skin-mimicking tissue model.

Development of an MRI-Compatible Needle Driver for In-Bore Prostate Biopsy

Minimally invasive percutaneous approaches routinely employ insertion of needles into soft tissue for diagnostic or therapeutic purposes. Lack of targeting accuracy while inserting needles can significantly mitigate the effectiveness of these methods. Robot-assisted needle steering under magnetic resonance imaging (MRI) guidance is a viable option for reaching the target accurately. In this paper, we report the development of an MRI-compatible needle driver for in-bore prostate biopsy. The device easily mounts onto and works together with our previously developed MRI-compatible prostate interventional robot. It is the first robotic device using a standard biopsy gun, which is easily replaceable/detachable in case of multi-sampling biopsy applications. The mechanism enables rotation, translation, and triggering of the biopsy gun to steer the bevel needle through the tissue and to take samples accurately from the target loci. Using the rotational and translational capabilities, the same system can also assist brachytherapy needle placement. Preliminary experiments have shown that the design meets the requirements set by the clinical workflow. System feasibility was verified by multiple users inserting 2 different types of needles under visual feedback into a phantom made of soft plastic. The average targeting errors were 0.92 mm for 18 gauge biopsy and 1.65 mm for 20 gauge brachytherapy needle.

In-bore prostate transperineal interventions with an MRI-guided parallel manipulator: system development and preliminary evaluation

BACKGROUND

Robot-assisted minimally-invasive surgery is well recognized as a feasible solution for diagnosis and treatment of prostate cancer in humans.

METHODS

This paper discusses the kinematics of a parallel 4 Degrees-of-Freedom (DOF) surgical manipulator designed for minimally invasive in-bore prostate percutaneous interventions through the patient's perineum. The proposed manipulator takes advantage of four sliders actuated by MRI-compatible piezoelectric motors and incremental rotary encoders. Errors, mostly originating from the design and manufacturing process, need to be identified and reduced before the robot is deployed in clinical trials.

RESULTS

The manipulator has undergone several experiments to evaluate the repeatability and accuracy (about 1 mm in air (in x or y direction) at the needle's reference point) of needle placement, which is an essential concern in percutaneous prostate interventions.

CONCLUSION

The acquired results endorse the sustainability, precision and reliability of the manipulator. Copyright © 2015 John Wiley & Sons, Ltd.

AAPM and GEC-ESTRO guidelines for image-guided robotic brachytherapy: report of Task Group 192

In the last decade, there have been significant developments into integration of robots and automation tools with brachytherapy delivery systems. These systems aim to improve the current paradigm by executing higher precision and accuracy in seed placement, improving calculation of optimal seed locations, minimizing surgical trauma, and reducing radiation exposure to medical staff. Most of the applications of this technology have been in the implantation of seeds in patients with early-stage prostate cancer. Nevertheless, the techniques apply to any clinical site where interstitial brachytherapy is appropriate. In consideration of the rapid developments in this area, the American Association of Physicists in Medicine (AAPM) commissioned Task Group 192 to review the state-of-the-art in the field of robotic interstitial brachytherapy. This is a joint Task Group with the Groupe Européen de Curiethérapie-European Society for Radiotherapy & Oncology (GEC-ESTRO). All developed and reported robotic brachytherapy systems were reviewed. Commissioning and quality assurance procedures for the safe and consistent use of these systems are also provided. Manual seed placement techniques with a rigid template have an estimated in vivo accuracy of 3-6 mm. In addition to the placement accuracy, factors such as tissue deformation, needle deviation, and edema may result in a delivered dose distribution that differs from the preimplant or intraoperative plan. However, real-time needle tracking and seed identification for dynamic updating of dosimetry may improve the quality of seed implantation. The AAPM and GEC-ESTRO recommend that robotic systems should demonstrate a spatial accuracy of seed placement ≤1.0 mm in a phantom. This recommendation is based on the current performance of existing robotic brachytherapy systems and propagation of uncertainties. During clinical commissioning, tests should be conducted to ensure that this level of accuracy is achieved. These tests should mimic the real operating procedure as closely as possible. Additional recommendations on robotic brachytherapy systems include display of the operational state; capability of manual override; documented policies for independent check and data verification; intuitive interface displaying the implantation plan and visualization of needle positions and seed locations relative to the target anatomy; needle insertion in a sequential order; robot-clinician and robot-patient interactions robustness, reliability, and safety while delivering the correct dose at the correct site for the correct patient; avoidance of excessive force on radioactive sources; delivery confirmation of the required number or position of seeds; incorporation of a collision avoidance system; system cleaning, decontamination, and sterilization procedures. These recommendations are applicable to end users and manufacturers of robotic brachytherapy systems.

Three-axis MR-conditional robot for high-intensity focused ultrasound for treating prostate diseases transrectally

BACKGROUND

A prototype magnetic resonance image (MRI)-conditional robot was developed for navigating a high-intensity focused ultrasound (HIFU) system in order to treat prostate cancer transrectally.

MATERIALS AND METHODS

The developed robotic device utilizes three PC-controlled axes: a linear axis for motion along the rectum, an angular axis for rotation in the rectum, and a linear axis to lift the robot up and down. Experiments with the system were performed in a 1.5-T MRI system using gel phantoms.

RESULT

The robot was successfully operated in a 1.5-T clinical MRI system. The effect of piezoelectric motors and optical encoders was quantified based on the reduction of signal to noise ratio. Discrete and overlapping lesions were created accurately by moving the HIFU transducer with the robotic device.

CONCLUSION

An MRI-conditional HIFU robot was developed which can create controlled thermal lesions under MRI guidance. The intention is to use this robot transrectally in the future for the treatment of prostate cancer.

Robotic ultrasound and needle guidance for prostate cancer management: review of the contemporary literature

PURPOSE OF REVIEW

To present the recent advances in needle guidance and robotic ultrasound technology which are used for prostate cancer (PCa) diagnosis and management.

RECENT FINDINGS

Prostate biopsy technology has remained relatively unchanged. Improved needle localization and precision would allow for better management of this common disease. Robotic ultrasound and needle guidance is one strategy to improve needle localization and diagnostic accuracy of PCa. This review focuses on the recent advances in robotic ultrasound and needle guidance technologies, and their potential impact on PCa diagnosis and management.

SUMMARY

The use of robotic ultrasound and robotic-assisted needle guidance has the potential to improve PCa diagnosis and management.

Review of MRI positioning devices for guiding focused ultrasound systems

BACKGROUND

This article contains a review of positioning devices that are currently used in the area of magnetic resonance imaging (MRI) guided focused ultrasound surgery (MRgFUS).

METHODS

The paper includes an extensive review of literature published since the first prototype system was invented in 1991.

RESULTS

The technology has grown into a fast developing area with application to any organ accessible to ultrasound. The initial design operated using hydraulic principles, while the latest technology incorporates piezoelectric motors. Although, in the beginning there were fears regarding MRI safety, during recent years, the deployment of MR-safe positioning devices in FUS has become routine. Many of these positioning devices are now undergoing testing in clinical trials.

CONCLUSION

Existing MRgFUS systems have been utilized mostly in oncology (fibroids, brain, liver, kidney, bone, pancreas, eye, thyroid, and prostate). It is anticipated that, in the near future, there will be a positioning device for every organ that is accessible by focused ultrasound.