MR Safe Robotic Manipulator for MRI-Guided Intracardiac Catheterization

This paper introduces a robotic manipulator to realize robot-assisted intracardiac catheterization in magnetic resonance imaging (MRI) environment. MRI can offer high-resolution images to visualize soft tissue features such as scars or edema. We hypothesize that robotic catheterization, combined with the enhanced monitoring of lesions creation using MRI intraoperatively, will significantly improve the procedural safety, accuracy, and effectiveness. This is designed particularly for cardiac electrophysiological (EP) intervention, which is an effective treatment of arrhythmia. We present the first MR Safe robot for intracardiac EP intervention. The robot actuation features small hysteresis, effective force transmission, and quick response, which has been experimentally verified for its capability to precisely telemanipulate a standard clinically used EP catheter. We also present timely techniques for real-time positional tracking in MRI and intraoperative image registration, which can be integrated with the presented manipulator to im prove the performance of teleoperated robotic catheterization

fMRI-compatible rehabilitation hand device

BACKGROUND: Functional magnetic resonance imaging (fMRI) has been widely used in studying human brain functions and neurorehabilitation. In order to develop complex and well-controlled fMRI paradigms, interfaces that can precisely control and measure output force and kinematics of the movements in human subjects are needed. Optimized state-of-the-art fMRI methods, combined with magnetic resonance (MR) compatible robotic devices for rehabilitation, can assist therapists to quantify, monitor, and improve physical rehabilitation. To achieve this goal, robotic or mechatronic devices with actuators and sensors need to be introduced into an MR environment. The common standard mechanical parts can not be used in MR environment and MR compatibility has been a tough hurdle for device developers. METHODS: This paper presents the design, fabrication and preliminary testing of a novel, one degree of freedom, MR compatible, computer controlled, variable resistance hand device that may be used in brain MR imaging during hand grip rehabilitation. We named the device MR_CHIROD (Magnetic Resonance Compatible Smart Hand Interfaced Rehabilitation Device). A novel feature of the device is the use of Electro-Rheological Fluids (ERFs) to achieve tunable and controllable resistive force generation. ERFs are fluids that experience dramatic changes in rheological properties, such as viscosity or yield stress, in the presence of an electric field. The device consists of four major subsystems: a) an ERF based resistive element; b) a gearbox; c) two handles and d) two sensors, one optical encoder and one force sensor, to measure the patient induced motion and force. The smart hand device is designed to resist up to 50% of the maximum level of gripping force of a human hand and be controlled in real time. RESULTS: Laboratory tests of the device indicate that it was able to meet its design objective to resist up to approximately 50% of the maximum handgrip force. The detailed compatibility tests demonstrated that there is neither an effect from the MR environment on the ERF properties and performance of the sensors, nor significant degradation on MR images by the introduction of the MR_CHIROD in the MR scanner. CONCLUSION: The MR compatible hand device was built to aid in the study of brain function during generation of controllable and tunable force during handgrip exercising. The device was shown to be MR compatible. To the best of our knowledge, this is the first system that utilizes ERF in MR environment

Design and Validation of a MR-compatible Pneumatic Manipulandum

The combination of functional MR imaging and novel robotic tools may provide unique opportunities to probe the neural systems underlying motor control and learning. Here, we describe the design and validation of a MR-compatible, 1 degree-of-freedom pneumatic manipulandum along with experiments demonstrating its safety and efficacy. We first validated the robot\u27s ability to apply computer-controlled loads about the wrist, demonstrating that it possesses sufficient bandwidth to simulate torsional spring-like loads during point-to-point flexion movements. Next, we verified the MR-compatibility of the device by imaging a head phantom during robot operation. We observed no systematic differences in two measures of MRI signal quality (signal/noise and field homogeneity) when the robot was introduced into the scanner environment. Likewise, measurements of joint angle and actuator pressure were not adversely affected by scanning. Finally, we verified device efficacy by scanning 20 healthy human subjects performing rapid wrist flexions against a wide range of spring-like loads. We observed a linear relationship between joint torque at peak movement extent and perturbation magnitude, thus demonstrating the robot\u27s ability to simulate spring-like loads in situ. fMRI revealed task-related activation in regions known to contribute to the control of movement including the left primary sensorimotor cortex and right cerebellum

Dynamics and control of an MRI compatible master-slave system with hydrostatic transmission

Proceedings - IEEE International Conference on Robotics and Automation200421288-1294PIIA

Medical robots for MRI guided diagnosis and therapy

Magnetic Resonance Imaging (MRI) provides the capability of imaging tissue with fine resolution and superior soft tissue contrast, when compared with conventional ultrasound and CT imaging, which makes it an important tool for clinicians to perform more accurate diagnosis and image guided therapy. Medical robotic devices combining the high resolution anatomical images with real-time navigation, are ideal for precise and repeatable interventions. Despite these advantages, the MR environment imposes constraints on mechatronic devices operating within it. This thesis presents a study on the design and development of robotic systems for particular MR interventions, in which the issue of testing the MR compatibility of mechatronic components, actuation control, kinematics and workspace analysis, and mechanical and electrical design of the robot have been investigated. Two types of robotic systems have therefore been developed and evaluated along the above aspects. (i) A device for MR guided transrectal prostate biopsy: The system was designed from components which are proven to be MR compatible, actuated by pneumatic motors and ultrasonic motors, and tracked by optical position sensors and ducial markers. Clinical trials have been performed with the device on three patients, and the results reported have demonstrated its capability to perform needle positioning under MR guidance, with a procedure time of around 40mins and with no compromised image quality, which achieved our system speci cations. (ii) Limb positioning devices to facilitate the magic angle effect for diagnosis of tendinous injuries: Two systems were designed particularly for lower and upper limb positioning, which are actuated and tracked by the similar methods as the first device. A group of volunteers were recruited to conduct tests to verify the functionality of the systems. The results demonstrate the clear enhancement of the image quality with an increase in signal intensity up to 24 times in the tendon tissue caused by the magic angle effect, showing the feasibility of the proposed devices to be applied in clinical diagnosis

Modélisation et commande du moteur piézoélectrique à onde progressive

Piezoelectric motors are resonant vibromotors. They represent a new actuator generation in the field of servo-drives. In particular, the travelling wave ultrasonic motor presents a high torque at low speed, a zero speed torque without feeding, low sensitivity to electromagnetic disturbances as well as being a more compact solution if compared to conventional electromagnetic motors. Much researches has been performed by others to determine an analytical model based on the identification of an electromagnetic equivalent circuit or on exploitation of a theoretical model based on numerical approaches, which use finite elements methods. While leading to satisfactory analysis, these modeling methods can hardly be exploited in the design of control algorithms. Indeed, they require considerable processing resources to generate and visualize the results. For this reason, we introduce in this thesis, an analytical model that is easily adaptable to operational applications and control techniques. The proposed analytical model has been validated by comparing measured characteristics with those obtained in simulations, which was possible thanks to the realization of a modular test bench. The travelling wave ultrasonic motor is characterized by strong non-linearity. It also depends highly on the wear state of the materials, which is difficult to model, and on the contact surface between stator and rotor. In addition, the mechanical resonance frequency experiences drift due to the variations of temperature. These considerations of strong non-linearities and parameter sensitivities of the motor represent a challenge for the study and design of an efficient and robust control strategy. We introduce with this thesis a new control approach that guarantees a closed loop response which is independent of the motor operating point. Moreover, the proposed control method allows to avoid the discontinuities typically present with this type of actuator with a very reasonnable hardware requierments. Finally, an important extension in the product range of the piezoelectric actuators is proposed in the last part of this thesis. It acts to develop an fMRI (functional Magnetic Resonance Imaging) compatible haptic interface with one degree of freedom. The use of a robotic interface in conjunction with an fMRI environment would enable neuroscientists to investigate the brain mechanism used to perform tasks with arbitrary dynamics, and could become a critical tool in neuroscience and rehabilitaiton. There is, however, a major problem for robot working within an fMRI environment : conventional actuators and materials interfere with the strong permanent magnetic field and the fast switching magnetic field gradients. Consequently, non-ferromagnetic materials must be used to avoid forces on the device itself, that can compromise its performance and may result in hazardous conditions for the patient or the medical staff. In addition, the materials should be non-conducting to avoid the generation of eddy currents. The travelling wave ultrasonic motor was used because it provides benefits compared to the conventional electromagnetic actuators. Non-ferromagnetic piezoelectric ceramic material is used and as a result motor operation is not affected by the presence of the strong magnetic fields ecountered in the clinical scanners

MRI compatible mechatronic devices to aid medical diagnosis and intervention

Imperial Users onl