A 2-DOF fMRI Compatible Haptic Interface to Interact with Arm Movements

Hannes Bleuler, Etienne Burdet, Dominique Chapuis, Ludovic Dovat, Roger Gassert, Olivier Lambercy, Yves Ruffieux
2006
Conference paper

Abstract

This paper describes a two-degrees-of-freedom haptic interface to investigate the brain mechanisms of human motor control, which is capable of safely and gently interacting with human arm motion during functional magnetic resonance imaging (fMRI). A hydrostatic transmission separates the interface into a master and an MR-compatible slave system, allowing the placement of all interfering components outside the electromagnetic shield of the MR room.The transmission mirrors force and motion of the master actuators on the slave system placed close to the MR scanner. The parallel architecture takes advantage of the linear MR-compatible actuators and allows human subjects to perform reaching movements comfortably in the small workspace limited by thedimensions of the MR scanner and the biomechanics of the arm. The kinematic structure of the slave interface was optimized with respect to the available space and types of movements to beinvestigated. Materials were chosen based on their MR compatibility, their stiffness and weight. The interaction force with the subject is measured over two optical force sensors, located close to the output of the interface. Two shielded optoelectronic encoders measure the extension of the slave hydraulic pistons. Detailed tests demonstrated the fMRI compatibility even during movement of the interface.

Official source

https://infoscience.epfl.ch/record/85963?ln=en

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Related publications

Multi-Joint Arm Movements to Investigate Motor Control with fMRI

Hannes Bleuler, Etienne Burdet, Ludovic Dovat, Roger Gassert

Performing multi-joint arm movements in controllable dynamic environments during functional magnetic resonance imaging (fMRI) could provide important insights into the brain mechanisms involved in human motor control and related dysfunctions. In order to obtain useful data, these movements must be possible and comfortable for the subject within the narrow bore of the scanner and should not create any movement artifacts in the image. We found that commonly studied arm movements involving the shoulder create movement artifacts, and investigated alternative multijoint arm movements within a mock-up of an MR scanner. We selected movements involving the elbow and wrist joints, with an extension attached to the hand, and propose a dedicated kinematic structure using the MR compatible actuators we have previously developed.

2005

Robotic interfaces can dynamically interact with humans performing movements and can be used to study neuromuscular adaptation. Such devices can produce computer controlled dynamics during movement and measure the interaction force and movement trajectory. On the other hand, functional magnetic resonance imaging (fMRI) can provide insight into the functional organization and plasticity of the brain. Using a robotic interface in conjunction with fMRI could allow neuroscientists to investigate the brain mechanisms of manipulation and motor learning, give therapists a tool for adaptive and patient-specific rehabilitation therapies, and assist medical doctors in functional diagnostics of motor dysfunctions. However, the MR environment imposes severe safety and electromagnetic compatibility constraints on mechatronic components, and the accessible workspace around the subject is limited. In addition, interaction with human motion must be safe and gentle. This thesis investigates the MR compatibility and performances of mechatronic elements, and develops an fMRI-compatible robotic technology consisting of sensors and actuators as well as adequate safety, control and synchronization strategies. It thus becomes possible to design various robotic systems for interaction with human motion during fMRI. This novel technology is benchmarked through the realization of several MR-compatible robotic systems which are currently being used by neuroscience groups in Japan and Europe. These include a highly MR-compatible interface for wrist motion, a tactile finger stimulation device using both intrinsically compatible and electrically powered components, as well as a two-degrees-of-freedom interface to investigate the control of multi-joint arm movements. The MR compatibility of these devices is successfully tested using a protocol developed for the particularly sensitive functional MRI sequences. In a further step towards performing multi-joint arm movements during fMRI, movement-related artifacts and biomechanical constraints are examined, and movements suitable for motor control studies are identified. Preliminary experiments with the realized systems demonstrate the potential of such robotic interfaces: the brain activation patterns during mental simulation of wrist motion are different from the patterns obtained during actual movements in interaction with the interface, and activation patterns in all conditions agree with results from literature. The well-controlled conditions as well as the recorded position and force data during fMRI open up new possibilities in data analysis and may allow new insights into the brain mechanisms involved in human motor control.

EPFL2006