Dynamic Material Properties of Human and Animal Livers

Abstract

Accurate characterization of the mechanical properties of soft tissues is important for diagnosing medical pathologies and developing solutions for them. With the recent advances in technologies leading to the development of surgical simulators, medical robots, and computer-assisted surgical planning systems, this topic has gained even more importance. However, most of the earlier research studies conducted with animal and human livers have focused on the investigation of static (strain-dependent) material properties. The number of studies investigating the dynamic material properties (time and frequency-dependent) of animal and human livers are much less than the ones investigating the static material properties. In fact, there is almost no data available in the literature showing the variation in dynamic material properties of healthy or diseased human liver as a function of excitation frequency. MotivationSoft organ tissues exhibit complex nonlinear, anisotropic, non-homogeneous, time, and rate-dependent behavior. Fung [1] has revealed that nonlinear stress-strain relationship is common for soft tissues but the degrees are different for different tissues. Since soft organs are composed of different materials, like elastin and collagen, in different combinations, soft tissue properties are both coordinate and direction dependent. Time and rate dependent behavior is also common and explained by viscoelasticity.

Liver Bioreactor Design Issues of Fluid Flow and Zonation, Fibrosis, and Mechanics: A Computational Perspective

“…Kerdok et al [111] have used such a model to model small strain frequency indentation tests and large strain creep indentation tests. Basdogan [222] reviewed her work on fitting this model to the changes of mechanical behavior of human and animal livers with a degree of fibrosis. Note that a Maxwell model with one relaxation time constant is essentially equivalent to Biot's theory.…”

Local incompressible registration for liver ablation surgery assessment

“…However, the normal liver is a soft organ and can be considered as the incompressible tissue . For the incompressible tissue, the volume of this tissue hardly changes during the deformation . A nonrigid registration with volume‐preserving constraint is required for an accurate assessment.…”

“…Based on the replacement, the estimated deformation allows the tumor area to deform freely. However, the estimated deformation without an elastic constraint is not accurate for the incompressible biological tissue . Kim et al .…”

“…9 For the incompressible tissue, the volume of this tissue hardly changes during the deformation. [10][11][12][13] A nonrigid registration with volume-preserving constraint is required for an accurate assessment. However, the grayscale distributions of the tumor and ablation area are similar, and mismatching between the regions near the tumor and ablation area is inevitable in the nonrigid registration.…”

“…However, the estimated deformation without an elastic constraint is not accurate for the incompressible biological tissue. [9][10][11][12][13] Kim et al 18 proposed a method based on elastic registration. The method registers the post-to pre-MWA CT image with an elastic constraint to estimate the deformation caused by respiratory movement.…”