Combining quasi-static and high frequency experiments for the viscoelastic characterization of brain tissue

TL;DR

This study integrates quasi-static and high-frequency experimental data to develop a unified viscoelastic model of brain tissue, enhancing the accuracy of biomechanical simulations relevant to neurosurgery and brain research.

Contribution

It combines multi-scale experimental findings to calibrate a comprehensive viscoelastic model of brain tissue, addressing inconsistencies in prior literature.

Findings

Consistent regional variations in viscoelastic behavior across scales

Mechanical behavior shifts from elasticity to viscosity with frequency

Unified fractional Kelvin-Voigt model accurately represents tissue mechanics

Abstract

Mechanical models of brain tissue are a beneficial tool to simulate neurosurgical interventions, disease progression, or brain development. However, the accuracy and predictive capacity of such a model relies on a precise experimental characterization of the tissue's mechanical behavior. Such a characterization is yet limited by inconsistent or contradictory experimental responses reported in the literature, particularly when measurements are performed in different time or length scales. Although brain tissue has been extensively investigated in previous studies, the combination of experimental findings from different scales has received limited attention. In this study, we combine ex vivo mechanical responses of porcine brain tissue obtained at different time scales in a mechanical model. We investigated the mechanical behavior of three different brain regions in the quasi-static domain with multi-modal large strain rheometer measurements and at high frequencies with magnetic resonance elastography (MRE). A comparative analysis of the mechanical parameters obtained from both experimental techniques demonstrated consistent regional variations in the viscoelastic behavior across the two domains. However, the mechanical behavior changes from a higher elasticity in the quasi-static and low frequency domain to a dominating viscosity at high frequencies. Based on the quasi-static and the high frequency behavior, we calibrated a fractional Kelvin-Voigt model and consequently unified the two responses in a single mechanical model to obtain a comprehensive characterization of the tissue's mechanical behavior.