Design and Evaluation of a Cable-Driven fMRI-Compatible Haptic Interface to Investigate Precision Grip Control

Abstract

Our hands and fingers are involved in almost all activities of daily living and, as such, have a disproportionately large neural representation. Functional magnetic resonance imaging investigations into the neural control of the hand have revealed great advances, but the harsh MRI environment has proven to be a challenge to devices capable of delivering a large variety of stimuli necessary for well-controlled studies. This paper presents a fMRI-compatible haptic interface to investigate the neural mechanisms underlying precision grasp control. The interface, located at the scanner bore, is controlled remotely through a shielded electromagnetic actuation system positioned at the end of the scanner bed and then through a high stiffness, low inertia cable transmission. We present the system design, taking into account requirements defined by the biomechanics and dynamics of the human hand, as well as the fMRI environment. Performance evaluation revealed a structural stiffness of 3.3 N/mm, renderable forces up to 94 N, and a position control bandwidth of at least 19 Hz. MRI-compatibility tests showed no degradation in the operation of the haptic interface or the image quality. A preliminary fMRI experiment during a pilot study validated the usability of the haptic interface, illustrating the possibilities offered by this device.

An MR-Compatible Haptic Interface With Seven Degrees of Freedom

“…Our design requirements in terms of actuated DoF are met and rotations of ±30 • can be achieved in the dexterous workspace with a volume of 14137 mm 3 . The desired minimum output capabilities in terms of force and acceleration are also achieved.…”

“…The advantages and disadvantages of these actuation principles were discussed in [2]. The state-of-the-art has been extended since, and recent key developments were an MR-compatible gripper [3] as well as a wrist mechanism [4]. Both of the devices provide one DoF and are based on cable transmissions from a remotely located dc motor.…”

Quantitative Testing of fMRI-Compatibility of an Electrically Active Mechatronic Device for Robot-Assisted Sensorimotor Protocols

“…In the pursuit of combining accurate kinesthetic feedback during sensorimotor protocols with simultaneous observation of brain activity via fMRI, researchers have endeavored to build MR-compatible haptic devices to support unconstrained hand movements [12], [21]- [23], hand/finger grasp [7], [24], [25], and foot movements [13], [26]. Such devices need to adhere to strict requirements for MR-compatibility, such as i) avoiding the use of magnetic materials to prevent distortion of the static magnetic field, ii) minimizing electromagnetic signals in both the radio-frequency (RF) and audible range to avoid interference with the RF-transceiver and gradients subsystems used in MRI, and iii) limiting use of in-bore electrical conductors to avoid coupling of eddy currents and Different no.…”

Fiber-Optic Force Sensors for MRI-Guided Interventions and Rehabilitation: A Review

“…These sensors provide repeatable experimental conditions to facilitate the investigation of the relation between human cognition and behavior. The applications range from the fMRI-compatible wrist robotic interface with fiber optic position sensor to study brain development in neonates [5] and adults [6], to the investigation of hand precision grip control with a cable-driven fMRI-compatible haptic interface using fiber optic force sensors [7]. The sensing range and resolution of both sensors were optimized for the specific application and could readily be designed for other sensing range or resolutions (different flexure geometry or materials, detector sensitivity, etc).…”