Individual Muscle Force Estimation in the Human Forearm Using Multi-Muscle MR Elastography (MM-MRE)

Area of Science:

• Biomechanics
• Musculoskeletal Imaging
• Medical Physics

Background:

• Muscle contraction involves complex mechanical changes that are challenging to quantify non-invasively.
• Magnetic Resonance Elastography (MRE) is a technique that measures tissue stiffness.
• Understanding individual muscle contributions during functional tasks is crucial for diagnosing and treating musculoskeletal disorders.

Purpose of the Study:

• To assess the sensitivity of MRE to active muscle contraction in forearm muscles.
• To develop a method for estimating individual muscle force using MRE.

Main Methods:

• MRE was combined with an MRI-compatible device (MREbot) to measure forearm muscle mechanical properties and wrist joint torque during isometric tasks.
• Shear wave speed was measured in thirteen forearm muscles across various contractile states and wrist postures.
• A force estimation algorithm based on a musculoskeletal model was applied to MRE data.

Main Results:

• Shear wave speed significantly varied with muscle recruitment (agonist/antagonist), torque amplitude, and wrist posture.
• Increased shear wave speed was observed during both agonist and antagonist muscle contractions, correlating with loading levels.
• MRE measurements explained an average of 70% of the variance in measured joint torque.

Conclusions:

• MRE effectively captures variations in muscle shear wave speed related to muscle activation.
• A novel method for estimating individual muscle force from MRE measurements was demonstrated.
• MM-MRE holds potential for characterizing normal and abnormal muscle co-contraction patterns in the forearm.