Gregory S. Fischer

MRI-Compatible Pneumatic Robot for Transperineal Prostate Needle Placement

Magnetic resonance imaging (MRI) can provide high-quality 3-D visualization of prostate and surrounding tissue, thus granting potential to be a superior medical imaging modality for guiding and monitoring prostatic interventions. However, the benefits cannot be readily harnessed for interventional procedures due to difficulties that surround the use of high-field (1.5T or greater) MRI. The inability to use conventional mechatronics and the confined physical space makes it extremely challenging to access the patient. We have designed a robotic assistant system that overcomes these difficulties and promises safe and reliable intraprostatic needle placement inside closed high-field MRI scanners. MRI compatibility of the robot has been evaluated under 3T MRI using standard prostate imaging sequences and average SNR loss is limited to 5%. Needle alignment accuracy of the robot under servo pneumatic control is better than 0.94 mm rms per axis. The complete system workflow has been evaluated in phantom studies with accurate visualization and targeting of five out of five 1 cm targets. The paper explains the robot mechanism and controller design, the system integration, and presents results of preliminary evaluation of the system.

OpenIGTLink: an open network protocol for image-guided therapy environment

With increasing research on system integration for image‐guided therapy (IGT), there has been a strong demand for standardized communication among devices and software to share data such as target positions, images and device status.

Development of a pneumatic robot for MRI-guided transperineal prostate biopsy and brachytherapy: New approaches

Magnetic Resonance Imaging (MRI) guided prostate biopsy and brachytherapy has been introduced in order to enhance the cancer detection and treatment. For the accurate needle positioning, a number of robotic assistants have been developed. However, problems exist due to the strong magnetic field and limited workspace. Pneumatically actuated robots have shown the minimum distraction in the environment but the confined workspace limits optimal robot design and thus controllability is often poor. To overcome the problem, a simple external damping mechanism using timing belts was sought and a 1-DOF mechanism test result indicated sufficient positioning accuracy. Based on the damping mechanism and modular system design approach, a new workspace-optimized 4-DOF parallel robot was developed for the MRI-guided prostate biopsy and brachytherapy. A preliminary evaluation of the robot was conducted using previously developed pneumatic controller and satisfying results were obtained.

An open-source research kit for the da Vinci® Surgical System

We present a telerobotics research platform that provides complete access to all levels of control via open-source electronics and software. The electronics employs an FPGA to enable a centralized computation and distributed I/O architecture in which all control computations are implemented in a familiar development environment (Linux PC) and low-latency I/O is performed over an IEEE-1394a (FireWire) bus at speeds up to 400 Mbits/sec. The mechanical components are obtained from retired first-generation da Vinci ® Surgical Systems. This system is currently installed at 11 research institutions, with additional installations underway, thereby creating a research community around a common open-source hardware and software platform.

A dual-armed robotic system for intraoperative ultrasound guided hepatic ablative therapy: a prospective study

There has been increased interest in minimally invasive ablative treatments that typically require precise placement of the ablator tool to meet the predefined planning and lead to efficient tumor destruction. Standard ablative procedures involve free hand transcutaneous ultrasonography (TCUS) in conjunction with manual tool positioning. Unfortunately, existing TCUS systems suffer from many limitations and result in failure to identify nearly half of all treatable liver lesions. Freehand manipulation of the ultrasound (US) probe and ablator tool lacks the critical level of control, accuracy, stability, and guaranteed performance required for these procedures. Freehand US results in undefined gap distribution, anatomic deformation due to variable pressure from the sonographers hand, and severe difficulty in maintaining optimal scanning position. In response to these limitations, we propose the use of a dual robotic arm system that manages both ultrasound manipulation and needle guidance. We report a prototype of the dual arm system and a comparative performance analysis between robotic vs. freehand systems, for both US scanning and needle placement in mechanical and animal tissue phantoms.

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.

A Modular 2-DOF Force-Sensing Instrument For Laparoscopic Surgery

Minimally Invasive Surgery (MIS) has enjoyed increasing attention and development over the last two decades. As MIS systems evolve, the surgeon is increasingly insulated from patient contact, creating a trade-off between surgi- cal sensory information and patient invasiveness. Incorporation of haptic feed- back into MIS systems promises to restore sensory information surrendered in favor of minimal invasiveness. We have developed a novel, biocompatible 2- DOF force-sensing sleeve that can be used modularly with a variety of 5mm laparoscopic instruments. The functional requirements for such a device are de- fined, and design strategies are explored. Our formal device design is outlined and device calibration is presented with derived calibration functions. Illustrative experimental force data from a porcine model is presented. This device can be used for intra-abdominal force recording and feedback in laparoscopic environ- ments; the implications and future potential for this technology are explored.

MRI Compatibility of Robot Actuation Techniques --- A Comparative Study

This paper reports an experimental evaluation of the following three different MRI-compatible actuators: a Shinsei ultrasonic motor a Nanomotion ultrasonic motor and a pneumatic cylinder actuator. We report the results of a study comparing the effect of these actuators on the signal to noise ratio (SNR) of MRJ images under a variety of experimental conditions. Evaluation was performed with the controller inside and outside the scanner room and with both 1.5T and 3T MRI scanners. Pneumatic cylinders function with no loss of SNR with controller both inside and outside of the scanner room. The Nanomotion motor performs with moderate loss of SNR when moving during imaging. The Shinsei is unsuitable for motion during imaging. All may be used when motion is appropriately interleaved with imaging cycles.

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.

Dynamic MRI scan plane control for passive tracking of instruments and devices

This paper describes a novel image-based method for tracking robotic mechanisms and interventional devices during Magnetic Resonance Image (MRI)-guided procedures. It takes advantage of the multi-planar imaging capabilities of MRI to optimally image a set of localizing fiducials for passive motion tracking in the image coordinate frame. The imaging system is servoed to adaptively position the scan plane based on automatic detection and localization of fiducial artifacts directly from the acquired image stream. This closed-loop control system has been implemented using an open-source software framework and currently operates with GE MRI scanners. Accuracy and performance were evaluated in experiments, the results of which are presented here.