Quantitative diffusion tensor MRI-based fiber tracking of human skeletal muscle

Area of Science:

• Biomedical Engineering
• Human Anatomy
• Medical Imaging

Background:

• Understanding skeletal muscle structure-function relationships is crucial for biomechanics and clinical applications.
• Diffusion-tensor magnetic resonance imaging (DT-MRI) provides detailed insights into muscle architecture.
• Pennation angle, a key parameter, influences muscle force production and requires accurate measurement techniques.

Purpose of the Study:

• To establish the feasibility of in vivo human DT-MRI fiber tracking for pennation angle measurement.
• To investigate heterogeneity in pennation angle within the tibialis anterior (TA) muscle.
• To test if aponeurosis orientation variability causes pennation angle heterogeneity.

Main Methods:

• Acquired T(1)-weighted anatomical and DT-MRI data of the tibialis anterior muscle in eight healthy subjects.
• Tracked muscle fibers using the principal eigenvector from DT-MRI data.
• Calculated pennation angles by determining the orientation of muscle fibers relative to the aponeurosis.

Main Results:

• Muscle fiber orientations remained consistent along the superior-inferior axis.
• Aponeurosis axial orientation varied significantly (~40 degrees), while sagittal and coronal orientations showed minimal changes.
• Pennation angle (theta) decreased from superior to inferior within the TA muscle (16.3° to 11.4°).
• Mean pennation angle was higher in the deep compartment compared to the superficial compartment.

Conclusions:

• DT-MRI fiber tracking is a feasible method for measuring human muscle pennation angles.
• The tibialis anterior muscle exhibits heterogeneity in pennation properties along its length.
• Aponeurosis orientation variability is a significant factor contributing to pennation angle heterogeneity in skeletal muscle.