Pressure based MRI-compatible muscle fascicle length and joint angle estimation.

Area of Science:

• Biomedical Engineering
• Neuroscience
• Rehabilitation Technology

Background:

• Functional magnetic resonance imaging (fMRI) is crucial for understanding central nervous system (CNS) neurophysiology and neuropathologies.
• Accurate fMRI studies rely on real-time monitoring of subject task performance, which is challenging with current technology.
• Existing MRI-compatible sensors cannot measure muscle fascicle length, limiting insights into peripheral and central nervous system interactions, especially in amputee populations.

Purpose of the Study:

• To develop a novel, low-cost, MRI-compatible sensor for real-time muscle fascicle length and joint angle estimation.
• To assess the sensor's accuracy and reliability in measuring muscular motion during functional magnetic resonance imaging (fMRI) studies.
• To expand the application of such sensors to diverse populations, including those with amputations.

Main Methods:

• Proposed a lightweight, skin impedance-insensitive pressure-based muscular motion sensor (pMMS) utilizing air pocket pressure changes.
• Developed a method to estimate muscle fascicle length and joint angle from pressure readings based on muscle-skin-sensor interaction dynamics.
• Validated the pMMS accuracy using ultrasound imaging for muscle fascicle length and joint encoders for ankle joint angle in biologically intact subjects.

Main Results:

• A single pMMS accurately estimated tibialis anterior (TA) muscle fascicle length and ankle joint angle during dorsiflexion.
• Differential pressure readings from two pMMSs mitigated errors from perturbations, enabling accurate estimation across a full range of motion.
• The sensor demonstrated robustness and reliability in various movement speeds and amplitudes.

Conclusions:

• The developed pressure-based muscular motion sensor (pMMS) is feasible for integration into fMRI settings.
• This technology enables real-time monitoring of subject movements, facilitating more sophisticated fMRI study designs.
• The pMMS offers a pathway to deeper understanding of neurophysiology and improved rehabilitation strategies.