Optimization of a Multifrequency Magnetic Resonance Elastography Protocol for the Human Brain.

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Brain stiffness measurements using magnetic resonance elastography (MRE) are frequency-dependent, hindering cross-study comparisons.
• Accurate rheological parameter acquisition for whole brain (WB), white matter (WM), and gray matter (GM) requires optimized actuation frequencies.

Purpose of the Study:

• To determine optimal actuation frequencies for accurate rheological parameter estimation in the human brain using MRE.
• To establish a foundation for region-specific multifrequency MRE protocols.

Main Methods:

• Six healthy volunteers underwent MRE on a 3T scanner using a modified spin-echo EPI sequence.
• Frequency-dependent tissue response data (20-80 Hz) were analyzed using four viscoelastic models (Maxwell, Kelvin-Voigt, Springpot, Zener).
• Bayesian Information Criterion (BIC) was used to identify the optimal combination of three actuation frequencies for WB, WM, and GM, minimizing fitting error.

Main Results:

• The Zener and Springpot models best approximated multifrequency tissue responses.
• Optimal frequency combinations for the Zener and Springpot models for WB were identified as 30-60-70 Hz and 30-40-80 Hz, respectively.

Conclusions:

• Optimal actuation frequencies were determined for accurate rheological parameter estimation in WB, WM, and GM.
• This study represents a crucial first step toward developing region-specific multifrequency MRE protocols for the brain.