Open-source, MRI-compatible grip force sensor for dynamic muscle imaging

Dynamic MRI synchronised with neuromuscular electrical stimulation (NMES) offers a reproducible method for assessing muscle activity but requires MRI-compatible force sensors to correlate quantitative muscle dynamics parameters with muscle force output. Most available sensors are expensive, rely on non-free software or are MR-incompatible This work presents an open-source, low-cost, MR-compatible grip force sensor as a viable alternative to commercial devices.

Phantom measurements were performed with and without the sensor at a 3T MRI to assess the MRI compatibility and its impact on image quality, field homogeneity and signal-to-noise ratio (SNR). Furthermore, the force sensor was integrated into a dynamic MRI setup with NMES and applied in vivo to four subjects.

The force sensor demonstrated good compatibility with a 3 T MRI scanner, exhibiting minimal SNR reduction and minimal increase in B₀ inhomogeneities in phantom measurements. During dynamic MRI with NMES, a 2D in-plane phase-contrast MRI sequence successfully retrieved the muscle's velocity field, proving effective for dynamic MRI applications, while preserving image quality.

The design of the force sensor, building instructions and software are publicly released as open source. This allows the proposed sensor to be adapted in multiple applications where grip force needs to be recorded in an MR scanner.