Viscoelasticity of subcortical gray matter structures

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Viscoelastic mechanical properties of the brain, measured by magnetic resonance elastography (MRE), are sensitive indicators of microstructural tissue health, particularly in neurodegenerative conditions.
• Recent research focuses on localized MRE measurements in specific neuroanatomical regions affected differently by disease.

Purpose of the Study:

• To present a novel method for measuring viscoelasticity in subcortical gray matter (SGM) structures.
• To assess the viscoelastic differences between various SGM structures and the global cerebrum in healthy individuals.
• To evaluate the reliability and uncertainty of the proposed MRE method for SGM analysis.

Main Methods:

• High spatial resolution MRE imaging (1.6 mm isotropic voxels) was employed.
• A mechanical inversion scheme with soft prior regularization (SPR) was incorporated to enhance local MRE measures in pre-defined SGM regions.
• The method was tested on 21 healthy young volunteers, with repeated measurements on one individual to estimate uncertainty.

Main Results:

• Subcortical gray matter structures (amygdala, hippocampus, caudate, putamen, pallidum, thalamus) exhibit distinct viscoelastic properties (shear stiffness and damping ratio).
• These SGM structures also differ in viscoelasticity from the global cerebrum.
• The method demonstrated a measurement uncertainty between 3% and 7% for SGM viscoelasticity.
• Higher spatial resolution and SPR were shown to decrease uncertainty and increase the sensitivity of SGM measures.

Conclusions:

• The developed MRE method enables reliable and sensitive measurement of viscoelasticity in SGM structures.
• This technique holds promise for future studies investigating neurodegenerative conditions affecting these brain regions.
• The findings highlight the potential of MRE for characterizing regional brain tissue properties.