Quantitative Analysis of Tissue Damage Evolution in Porcine Liver With Interrupted Mechanical Testing Under Tension, Compression, and Shear

Abstract

In this study, the damage evolution of liver tissue was quantified at the microstructural level under tensile, compression, and shear loading conditions using an interrupted mechanical testing method. To capture the internal microstructural changes in response to global deformation, the tissue samples were loaded to different strain levels and chemically fixed to permanently preserve the deformed tissue geometry. Tissue microstructural alterations were analyzed to quantify the accumulated damages, with damage-related parameters such as number density, area fraction, mean area, and mean nearest neighbor distance (NND). All three loading states showed a unique pattern of damage evolution, in which the damages were found to increase in number and size, but decrease in NND as strain level increased. To validate the observed damage features as true tissue microstructural damages, more samples were loaded to the above-mentioned strain levels and then unloaded back to their reference state, followed by fixation. The most major damage-relevant features at higher strain levels remained after the release of the external loading, indicating the occurrence of permanent inelastic deformation. This study provides a foundation for future structure-based constitutive material modeling that can capture and predict the stress-state dependent damage evolution in liver tissue.

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“…The details about porcine liver tissue properties characterization can be found in previous work. 6,7,13,36,38 According to our literature survey, the porcine liver stated in the work of Chui et al 7 is most similar to ours. Despite our result in Fig.…”

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“…It can also be used to characterize the mechanical properties of other soft tissues such as kidney, spleen, and brain tissues. Before the test, we carefully identified the unloaded state of each specimen so that we can eliminate the effect of gravity, which may explain why the stress-stretch curves we obtained are different from some studies (see, e.g., Roan and Vemaganti, [26]; Chen et al, [5]), where they tested the specimen without a well-defined unloaded state. How- ever, when compared with the work of Chui et al [6], where the unloaded state was properly considered, we observed a similar magnitude of stress.…”

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