Anisotropic behaviour of human gallbladder walls.

Area of Science:

• Biomechanics
• Medical Imaging
• Soft Tissue Mechanics

Background:

• Accurate biomechanical parameter estimation is crucial for patient-specific modeling and disease diagnosis.
• Non-invasive methods for soft tissue analysis are clinically significant.
• Understanding gallbladder wall mechanics aids in diagnosing pain related to gallbladder conditions.

Purpose of the Study:

• To propose a fully nonlinear approach for estimating human gallbladder wall muscle mechanical properties.
• To determine constitutive parameters using in vivo ultrasound images.
• To investigate the anisotropic nature of the gallbladder wall during passive refilling.

Main Methods:

• A nonlinear iterative approach using a modified Hozapfel-Gasser-Ogden constitutive law.
• Determination of five constitutive parameters by comparing computed displacements with ultrasound images.
• Utilizing MATLAB, Python, and ABAQUS for the optimization process.

Main Results:

• The human gallbladder wall exhibits anisotropic behavior during passive refilling.
• Peak stress is 1.6 times greater than predicted by linear mechanics due to unconsidered wall thickness reduction.
• Accounting for wall thickness changes allows linear models to correlate gallbladder stress with pain.

Conclusions:

• The proposed nonlinear method provides a more accurate understanding of human gallbladder biomechanics.
• Discrepancies between linear and nonlinear models highlight the importance of considering deformation-induced thickness changes.
• This research offers insights into the nonlinear characteristics of the gallbladder wall, relevant for clinical applications.