Magnetic resonance compatible stimulation device capable of providing passive and active finger movements

The purpose of this study is to develop a magnetic resonance (MR)-compatible stimulation device that can passively and actively provide flexion and extension movements to the two joints of the fingers independently without limiting the hand posture, and confirm the feasibility of the device through an MR-compatibility experiment and fMRI experiment. The developed device is composed of four parts: a control unit, power unit containing non-magnetic ultrasonic motors, wearable exoskeleton hand part, and tube-rod mechanisms. Each tube-rod mechanism is a flexible power transmission that connects the power unit to the hand part, without limiting the user's hand posture. The device can move the metacarpal phalangeal (MP) and proximal interphalangeal (PIP) joints independently. For the MR-compatibility experiment, we measure the signal-to-noise ratio (SNR) of MR images and the angles of potentiometers attached to the joints of the hand part. In the fMRI experiment, passive and active movements are provided to the fingers of a healthy participant using the developed device. As a result, the maximum variation of the SNR was 3.0 %, which was low enough to be virtually negligible. Moreover, the developed device functioned properly in the MRI environment. We observed different brain activities with the passive and active movements, and the results agreed with the known phenomena. In conclusion, we could confirm the feasibility of the developed MR-compatible stimulation device.