Gregory A. Cole

A MRI-guided concentric tube continuum robot with piezoelectric actuation: A feasibility study

This paper presents a versatile magnetic resonance imaging (MRI) compatible concentric tube continuum robotic system. The system enables MR image-guided placement of a curved, steerable active cannula. It is suitable for a variety of clinical applications including image-guided neurosurgery and percutaneous interventions, along with procedures that involve accessing a desired image target, through a curved trajectory. This 6 degree-of-freedom (DOF) robotic device is piezoelectrically actuated to provide precision motion with joint-level precision of better than 0.03mm, and is fully MRI-compatible allowing simultaneous robotic motion and imaging with no image quality degradation. The MRI compatibility of the robot has been evaluated under 3 Tesla MRI using standard prostate imaging sequences, with an average signal to noise ratio loss of less than 2% during actuator motion. The accuracy of active cannula control was evaluated in benchtop trials using an external optical tracking system with RMS error in tip placement of 1.00mm. Preliminary phantom trials of three active cannula placements in the MRI scanner showed cannula trajectories that agree with our kinematic model, with a RMS tip placement error of 0.61 - 2.24 mm.

Real-time MRI-guided needle placement robot with integrated fiber optic force sensing

This paper presents the first prototype of a magnetic resonance imaging (MRI) compatible piezoelectric actuated robot integrated with a high-resolution fiber optic sensor for prostate brachytherapy with real-time in situ needle steering capability in 3T MRI. The 6-degrees-of-freedom (DOF) robot consists of a modular 3-DOF needle driver with fiducial tracking frame and a 3-DOF actuated Cartesian stage. The needle driver provides needle cannula rotation and translation (2-DOF) and stylet translation (1-DOF). The driver mimics the manual physician gesture by two point grasping. To render proprioception associated with prostate interventions, a Fabry-Perot interferometer based fiber optic strain sensor is designed to provide high-resolution axial needle insertion force measurement and is robust to large range of temperature variation. The paper explains the robot mechanism, controller design, optical modeling and opto-mechanical design of the force sensor. MRI compatibility of the robot is evaluated under 3T MRI using standard prostate imaging sequences and average signal noise ratio (SNR) loss is limited to 2% during actuator motion. A dynamic needle insertion is performed and bevel tip needle steering capability is demonstrated under continuous real-time MRI guidance, both with no visually identifiable interference during robot motion. Fiber optic sensor calibration validates the theoretical modeling with satisfactory sensing range and resolution for prostate intervention.

Robotic System for MRI-Guided Stereotactic Neurosurgery

Stereotaxy is a neurosurgical technique that can take several hours to reach a specific target, typically utilizing a mechanical frame and guided by preoperative imaging. An error in any one of the numerous steps or deviations of the target anatomy from the preoperative plan such as brain shift (up to 20 mm), may affect the targeting accuracy and thus the treatment effectiveness. Moreover, because the procedure is typically performed through a small burr hole opening in the skull that prevents tissue visualization, the intervention is basically “blind” for the operator with limited means of intraoperative confirmation that may result in reduced accuracy and safety. The presented system is intended to address the clinical needs for enhanced efficiency, accuracy, and safety of image-guided stereotactic neurosurgery for deep brain stimulation lead placement. The study describes a magnetic resonance imaging (MRI)-guided, robotically actuated stereotactic neural intervention system for deep brain stimulation procedure, which offers the potential of reducing procedure duration while improving targeting accuracy and enhancing safety. This is achieved through simultaneous robotic manipulation of the instrument and interactively updated in situ MRI guidance that enables visualization of the anatomy and interventional instrument. During simultaneous actuation and imaging, the system has demonstrated less than 15% signal-to-noise ratio variation and less than 0.20% geometric distortion artifact without affecting the imaging usability to visualize and guide the procedure. Optical tracking and MRI phantom experiments streamline the clinical workflow of the prototype system, corroborating targeting accuracy with three-axis root mean square error 1.38 ± 0.45 mm in tip position and 2.03 ± 0.58° in insertion angle.

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 intraoperative 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-T MRI scanner using standard imaging sequences and the signal-to-noise ratio 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 3-D Euclidean distance based on MRI volume segmentation of the image-guided robotic needle placement procedure.

MRI compatibility evaluation of a piezoelectric actuator system for a neural interventional robot

The work presented in this paper has been performed in furtherance of developing an MRI-compatible surgical robotic system, specifically targeting the neural intervention procedure for the treatment of Parkinson’s Syndrome known as deep brain stimulation (DBS). In this paper we discuss the construction and testing of the MR-compatible controller, sensors and actuators, and the compatibility testing we have done to validate the success of our efforts in eliminating signal interference. Our robotic system was tested on a Phillips Achieva 3 Tesla MRI machine under diagnostic T1 and T2, high speed FGRE and functional EPI imaging protocols. It has been shown to operate without introducing any statistically significant degradation in image quality. We have shown that the creation of an MR-compatible electronically controlled closed-loop robotic actuation system and linkage mechanism can be created successfully within a standard high-field diagnostic magnet with insignificant levels of signal interference.

Haptic system design for MRI-guided needle based prostate brachytherapy

This paper presents the design of a haptic system for prostate needle brachytherapy under magnetic resonance imaging (MRI) guidance. This haptic system consists of some recently developed MRI-compatible mechatronic devices, including a fiber optic force sensor and a piezoelectric motor actuated needle driver mounted on a specifically designed 3-axis linear stage. We first propose the teleoperation framework with system architecture, infrastructure and control algorithm for the master-slave haptic interface. Then we introduce some novel sensors and actuators for MRI-compatible mechatronic devices of this haptic system. We developed the force sensor which provides in-vivo measurement of needle insertion forces to render proprioception associated with the brachytherapy procedure. We discuss the sensing principle of the optical sensor which enables two degrees-of-freedom (DOF) torque measurement and one DOF force measurement. The second apparatus of this system is a high precision 3-axis linear stage actuated by piezoelectric motors and position sensed by optical linear and rotary encoders and all of them have proved good magnetic compatibility. The needle driver can simultaneously provide needle cannula rotation and stylet translation motion while the cannula translation is engendered by the stage. The independent rotation and translation motion of the cannula and stylet can increase the targeting accuracy while minimize the tissue deformation and damage. The master-slave haptic system is capable of positioning needle and sensing insertion forces thus increasing the operation autonomy, accuracy and reducing the operation time.

Closed-Loop Actuated Surgical System Utilizing Real-Time In-Situ MRI Guidance

Direct magnetic resonance imaging (MRI) guidance during surgical intervention would provide many benefits; most significantly, interventional MRI can be used for planning, monitoring of tissue deformation, realtime visualization of manipulation, and confirmation of procedure success. Direct MR guidance has not yet taken hold because it is often confounded by a number of issues including: MRI-compatibility of existing surgery equipment and patient access in the scanner bore. This paper presents a modular surgical system designed to facilitate the development of MRI-compatible intervention devices. Deep brain stimulation and prostate brachytherapy robots are the two examples that successfully deploying this surgical modules. Phantom and human imaging experiments validate the capability of delineating anatomical structures in 3T MRI during robot motion.

Design of a robotic system for MRI-guided deep brain stimulation electrode placement

Deep brain stimulation (DBS) is a technique for influencing brain function though the use of implanted electrodes. Direct magnetic resonance (MR) image guidance during DBS insertion would provide many benefits; most significantly, interventional MRI can be used for planning, monitoring of tissue deformation, real-time visualization of insertion, and confirmation of placement. The accuracy of standard stereotactic insertion is limited by registration errors and brain movement during surgery. With real-time acquisition of high-resolution MR images during insertion, probe placement can be confirmed intra-operatively. Direct MR guidance has not yet taken hold because it is often confounded by a number of issues including: MR-compatibility of existing stereotactic surgery equipment and patient access in the scanner bore. The high resolution images required for neurosurgical planning and guidance require high-field MR (1.5–3T); thus, any system must be capable of working within the constraints of a closed, long-bore diagnostic magnet. Currently, no technological solution exists to assist MRI guided neurosurgical interventions in an accurate, simple, and economical manner.We present the design of a robotic assistant system that overcomes these difficulties and promises safe and reliable electrode placement in the brain inside closed high-field MRI scanners. The robot performs the insertion under real-time 3T MR image guidance. This paper described analysis of the workspace requirements, MR compatibility evaluation, and mechanism design.

High-Field MRI-Compatible Needle Placement Robots for Prostate Interventions: Pneumatic and Piezoelectric Approaches

Magnetic resonance imaging (MRI) can be a very effective imaging modality for live guidance during surgical procedures. The rationale of MRI-guided surgery with robot-assistance is to perform surgical interventions utilizing “real-time” image feedback while minimize operation time and improves the surgical outcomes. However, challenges arise from electromagnetic compatibility within the high-field (1.5T or greater) MRI environment and mechanical constraints due to the confined close-bore space. This chapter reviews two distinct MRI-compatible approaches for image-guided transperineal prostate needle placement. It articulates the robotic mechanism, actuator and sensor design, controller design and system integration for a pneumatically actuated robotic needle guide and a piezoelectrically actuated needle placement system. The two degree-of-freedom (DOF) pneumatic robot with manual needle insertion has a signal to noise ratio (SNR) loss limited to 5% with alignment accuracy under servo pneumatic control better than 0.94mm per axis. While the 6-DOF piezoelectrically actuated robot is the first demonstration of a novel multi piezoelectric actuator drive with less than 2% SNR loss for high-field MRI operating at full speed during imaging. Preliminary experiments in phantom studies evaluates system MRI compatibility, workflow, visualization and targeting accuracy.

Approaches to creating and controlling motion in MRI

Magnetic Resonance Imaging (MRI) can provide three dimensional (3D) imaging with excellent resolution and sensitivity making it ideal for guiding and monitoring interventions. The development of MRI-compatible interventional devices is complicated by factors including: the high magnetic field strength, the requirement that such devices should not degrade image quality, and the confined physical space of the scanner bore. Numerous MRI guided actuated devices have been developed or are currently being developed utilizing piezoelectric actuators as their primary means of mechanical energy generation to enable better interventional procedure performance. While piezoelectric actuators are highly desirable for MRI guided actuation for their precision, high holding force, and non-magnetic operation they are often found to cause image degradation on a large enough to scale to render live imaging unusable. This paper describes a newly developed piezoelectric actuator driver and control system designed to drive a variety of both harmonic and non-harmonic motors that has been demonstrated to be capable of operating both harmonic and non-harmonic piezoelectric actuators with less than 5% SNR loss under closed loop control. The proposed system device allows for a single controller to control any supported actuator and feedback sensor without any physical hardware changes.