Implementation and evaluation of simultaneous video-electroencephalography and functional magnetic resonance imaging

The objective of this study was to demonstrate that the addition of simultaneous and synchronised video to electroencephalography (EEG)-correlated functional magnetic resonance imaging (fMRI) could increase recorded information without data quality reduction. We investigated the effect of placing EEG, video equipment and their required power supplies inside the scanner room, on EEG, video and MRI data quality, and evaluated video-EEG-fMRI by modelling a hand motor task. Gradient-echo, echo-planner images (EPI) were acquired on a 3-T MRI scanner at variable camera positions in a test object [with and without radiofrequency (RF) excitation], and human subjects. EEG was recorded using a commercial MR-compatible 64-channel cap and amplifiers. Video recording was performed using a two-camera custom-made system with EEG synchronization. An in-house script was used to calculate signal to fluctuation noise ratio (SFNR) from EPI in test object with variable camera positions and in human subjects with and without concurrent video recording. Five subjects were investigated with video-EEG-fMRI while performing hand motor task. The fMRI time series data was analysed using statistical parametric mapping, by building block design general linear models which were paradigm prescribed and video based. Introduction of the cameras did not alter the SFNR significantly, nor did it show any signs of spike noise during RF off conditions. Video and EEG quality also did not show any significant artefact. The Statistical Parametric Mapping{T} maps from video based design revealed additional blood oxygen level-dependent responses in the expected locations for non-compliant subjects compared to the paradigm prescribed design. We conclude that video-EEG-fMRI set up can be implemented without affecting the data quality significantly and may provide valuable information on behaviour to enhance the analysis of fMRI data

Development of a Compact Piezoworm Actuator For Mr Guided Medical Procedures

In this research, a novel piezoelectric actuator was developed to operate safely inside the magnetic resonance imaging (MRI) machine. The actuator based on novel design that generates linear and rotary motion simultaneously for higher needle insertion accuracy. One of the research main objectives is to aid in the selection of suitable materials for actuators used in this challenging environment. Usually only nonmagnetic materials are used in this extremely high magnetic environment. These materials are classified as MRI compatible materials and are selected to avoid hazardous conditions and image quality degradation. But unfortunately many inert materials to the magnetic field do not possess desirable mechanical properties in terms of hardness, stiffness and strength and much of the available data for MRI compatible materials are scattered throughout the literature and often too device specific . Furthermore, the fact that significant heating is experienced by some of these devices due to the scanner’s variable magnetic fields makes it difficult to draw general conclusions to support the choice of suitable material and typically these choices are based on a trial-and-error with extensive time required for prototype development and MRI testing of such devices. This research provides a quantitative comparison of several engineering materials in the MRI environment and comparison to theoretical behavior which should aid designers/engineers to estimate the MRI compatible material performance before the expensive step of construction and testing. This work focuses specifically on the effects in the MRI due to the material susceptibility, namely forces, torques, image artifacts and induced heating

Teleoperation of MRI-Compatible Robots with Hybrid Actuation and Haptic Feedback

Image guided surgery (IGS), which has been developing fast recently, benefits significantly from the superior accuracy of robots and magnetic resonance imaging (MRI) which is a great soft tissue imaging modality. Teleoperation is especially desired in the MRI because of the highly constrained space inside the closed-bore MRI and the lack of haptic feedback with the fully autonomous robotic systems. It also very well maintains the human in the loop that significantly enhances safety. This dissertation describes the development of teleoperation approaches and implementation on an example system for MRI with details of different key components. The dissertation firstly describes the general teleoperation architecture with modular software and hardware components. The MRI-compatible robot controller, driving technology as well as the robot navigation and control software are introduced. As a crucial step to determine the robot location inside the MRI, two methods of registration and tracking are discussed. The first method utilizes the existing Z shaped fiducial frame design but with a newly developed multi-image registration method which has higher accuracy with a smaller fiducial frame. The second method is a new fiducial design with a cylindrical shaped frame which is especially suitable for registration and tracking for needles. Alongside, a single-image based algorithm is developed to not only reach higher accuracy but also run faster. In addition, performance enhanced fiducial frame is also studied by integrating self-resonant coils. A surgical master-slave teleoperation system for the application of percutaneous interventional procedures under continuous MRI guidance is presented. The slave robot is a piezoelectric-actuated needle insertion robot with fiber optic force sensor integrated. The master robot is a pneumatic-driven haptic device which not only controls the position of the slave robot, but also renders the force associated with needle placement interventions to the surgeon. Both of master and slave robots mechanical design, kinematics, force sensing and feedback technologies are discussed. Force and position tracking results of the master-slave robot are demonstrated to validate the tracking performance of the integrated system. MRI compatibility is evaluated extensively. Teleoperated needle steering is also demonstrated under live MR imaging. A control system of a clinical grade MRI-compatible parallel 4-DOF surgical manipulator for minimally invasive in-bore prostate percutaneous interventions through the patient’s perineum is discussed in the end. The proposed manipulator takes advantage of four sliders actuated by piezoelectric motors and incremental rotary encoders, which are compatible with the MRI environment. Two generations of optical limit switches are designed to provide better safety features for real clinical use. The performance of both generations of the limit switch is tested. MRI guided accuracy and MRI-compatibility of whole robotic system is also evaluated. Two clinical prostate biopsy cases have been conducted with this assistive robot

A preliminary systems study of interface equipment for digitally programmed flight simulators

Design study of digitally programmed supersonic transport flight simulato

Aircraft electromagnetic compatibility

Illustrated are aircraft architecture, electromagnetic interference environments, electromagnetic compatibility protection techniques, program specifications, tasks, and verification and validation procedures. The environment of 400 Hz power, electrical transients, and radio frequency fields are portrayed and related to thresholds of avionics electronics. Five layers of protection for avionics are defined. Recognition is given to some present day electromagnetic compatibility weaknesses and issues which serve to reemphasize the importance of EMC verification of equipment and parts, and their ultimate EMC validation on the aircraft. Proven standards of grounding, bonding, shielding, wiring, and packaging are laid out to help provide a foundation for a comprehensive approach to successful future aircraft design and an understanding of cost effective EMC in an aircraft setting

Application of ultrasonic motors to MR-compatible haptic interfaces

Functional Magnetic Resonance Imagery (fMRI) is an imaging technique allowing the observation of brain activity. Haptic interfaces can be used in conjunction with fMRI to stimulate the subject while measuring brain activity. Using robotic stimulation over conventional methods offers repeatability, flexibility and the possibility of logging of different experiment variables. Such system becomes a powerful tool for neuroscience study, diagnostic and rehabilitation. The MR scanner with its high magnetic fields and radio frequency pulses is a harsh environment for a robotic system. Robots that can operate safely and do not induce disturbances in the imaging of the scanner are qualified as MR-compatible. The actuation of these robots is an important issue. Electrical power brought to the actuator represents an important source of interferences with the scanner. Since electrical motors cannot be introduced in the MR room, haptic interfaces are conventionally remotely actuated over a long transmission with the actuators placed outside of the MR room. In particular cases, such as the study of finger motion, small haptic interfaces with limited force ranges are required. Remote actuation methods impose transmission lengths and means that cannot be reduced nor scaled down thus imposing a trade-off between performances and size reduction in these applications. This work investigates an alternative actuator that can achieve high-quality force-interactions with the fingers. The Ultrasonic Motor (USM) is MR-compatible and offers good performances. But it is not well suited for force-feedback and may be hazardous for the users. To address these issues, mechanical solutions are investigated by using an electrical analogy applied to mechanical systems. A novel actuation system using the USM as a power source and a clutch to control the output torque is proposed: the Hybrid USM Clutch Actuator (HUCA). The first prototype validates the different mechanical concepts developed in this work. The second, MR-compatible, integrates a clutch based on electrorheological fluids (ER). MR-compatibility has been validated and performances evaluated. Since the HUCA has the unique property of behaving both like a force source and a velocity source, dedicated control schemes have been developed to implement impedance and admittance force control. These enable the display of stiff walls and the rendering of a wide range of impedances thanks to the overlap of their range of displayable impedances. Compared to the hydrostatic transmission actuation, the HUCA shows higher performances and user safety. Furthermore, the powering through electrical wires allows developments of multi-DOF interfaces

MRI-VisAct: a Bowden cable-driven MRI compatible series viscoelastic actuator

Presence of the strong magnetic fields in the Magnetic Resonance Imaging (MRI) environment limits the integration of robotic rehabilitation systems to the MRI process. The tendency to improve imaging quality by the amplification of magnetic field strength further tightens the bidirectional compatibility constraints on MRI compatible rehabilitation devices. We present the design, control, and characterization of MRI-VisAct—a low-cost, Bowden cable-actuated rotary series viscoelastic actuator that fulfills the bidirectional compatibility requirements to the maximum extend. Components of MRI-VisAct that are placed in the magnet room are built using nonconductive, diamagnetic MRI compatible materials, while ferromagnetic/paramagnetic components are placed in the control room, located outside the MRI room. Power and data transmission are achieved through Bowden-cables and fiber optics, respectively. This arrangement ensures that neuroimaging artifacts are minimized, while safety hazards are eliminated, and the device performance is not affected by the magnetic field. MRIVisAct works under closed-loop torque control enabled through series viscoelastic actuation. MRI-VisAct is fully customizable; it can serve as the building block of higher degrees of freedom MRI compatible robotic devices

Design and control of an MRI compatible series elastic actuator

Bidirectional compatibility requirements with Magnetic Resonance Imaging (MRI) have limited the adaptation of rehabilitation robots for use in MRI machines. In this paper, we present the design and control of a Bowden cable-actuated, MRI-compatible series elastic actuator (SEA) that aims to fulfil the bidirectional compatibility requirements to the maximum extend. The proposed device is built using nonconductive diamagnetic MRI compatible materials, fiber optic sensing units and a Bowden cable based actuation, such that imaging artifacts created under strong magnetic field required for neuro-imaging are minimized. In particular, utilization of Bowden-cable transmission enables the placement of the conventional non-MRI compatible control/signal processing units and electric actuators outside the MRI room. This approach not only helps avoid the MR interference caused by these parts and eliminates safety hazards within the MRI room, but also ensures that the performance of the device is not affected by the strong magnetic field, resulting in ideal bidirectional MRI compatibility. Use of a custom-built fiber optic encoder together with nonconductive leaf spring based elastic element enables torque outputs of the device to be measured and used for closed-loop torque control, rendering the system into a series elastic actuator. The proposed MRI compatible SEA is easily customizable and can be used as the building block of higher degrees of freedom MRI compatible robotic devices. Current prototype is validated to administer continuous torques up to 2 Nm with a torque control bandwidth of 1 Hz and a torque sensing resolution of 0.05 Nm