Effect of interstitial fluid pressure on shear wave elastography: an experimental and computational study

Area of Science:

• Biomedical Engineering
• Biophysics
• Medical Imaging

Background:

• Elevated interstitial fluid pressure (IFP) causes strain-induced stiffening in poroelastic tissues.
• Shear wave elastography (SWE) measures tissue stiffness by assessing shear wave velocity (SWV).
• The biomechanical link between IFP and tissue stiffening requires further elucidation.

Purpose of the Study:

• To investigate the relationship between interstitial fluid pressure (IFP) and shear wave velocity (SWV) using SWE.
• To understand the biomechanical principles governing IFP-induced tissue stiffening.
• To develop a model for non-invasive IFP measurement.

Main Methods:

• Performed SWE experiments on chicken breast tissue with dynamic IFP modulation.
• Utilized finite element modeling to explore material models (poroelastic vs. porohyperelastic) and boundary conditions (constrained vs. unconstrained).
• Investigated the influence of geometric linearity and nonlinearity on the SWV-IFP relationship.

Main Results:

• Demonstrated a significant positive correlation between SWV and IFP in experiments.
• Numerical models accurately reproduced the SWV-IFP relationship in unconstrained porohyperelastic tissues.
• Material nonlinearity was identified as the primary driver of stiffening, with geometric nonlinearity playing a minor role.
• Observed distinct SWV-IFP responses during pressure increase and decrease, suggesting dynamic effects.

Conclusions:

• The study establishes a link between IFP and SWV, supporting SWE for IFP estimation.
• Material nonlinearity is key to IFP-induced tissue stiffening.
• The developed model offers a framework for SWE analysis in poroelastic tissues, advancing non-invasive IFP monitoring.