Wide-band multifrequency MR elastography with a fractional viscoelastic model and nonlinear inversion for enhanced...

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Rheology

Background:

• Conventional magnetic resonance elastography (MRE) uses high-frequency external vibrations (30-60 Hz).
• This frequency range may miss diagnostically relevant low-frequency tissue responses.
• There is a need for MRE techniques that capture a wider range of mechanical behaviors.

Purpose of the Study:

• To develop and validate a wide-band, multifrequency MRE framework.
• To integrate intrinsic cardiac motion (≈1 Hz) with conventional MRE actuation.
• To reconstruct frequency-dependent tissue viscoelasticity using a Kelvin-Voigt fractional-derivative (KVFD) model.

Main Methods:

• A novel wide-band multifrequency MRE approach combining intrinsic cardiac motion and external actuation.
• Reconstruction of tissue mechanics using a three-parameter KVFD model (θ₀, α, ω₀).
• Validation using COMSOL simulations, tofu-PVA phantoms, and in-vivo hepatic metastasis imaging.

Main Results:

• The KVFD model accurately estimated baseline stiffness (θ₀), fractional exponent (α), and reference frequency (ω₀) in simulations with noise.
• Phantom studies demonstrated sensitivity to both stiffness and frequency-dependent dispersion.
• In-vivo liver metastasis imaging showed lesion contrast comparable to clinical MRI, with unique dispersion signatures.

Conclusions:

• Integrating low-frequency intrinsic motion expands MRE's mechanical bandwidth.
• The KVFD model provides stable, spatially resolved biomarkers capturing frequency-dependent behavior.
• This advanced MRE technique enhances lesion detection and characterization, particularly in oncology.