A theoretical model for the elastic properties of very soft tissues

A theoretical model is developed to predict the elastic properties of very soft tissues such as glands, tumors and brain. Tissues are represented as r egular arrays of polyhedral (cubic or tetrakaidecahedral) cells, surrounded by extracellular spaces of uniform width. Cells are assumed to be incompre ssible, with very low resistance to shear deformation. Tissue shear rigidit y is assumed to result mainly from the extracellular matrix, which is treat ed as a compressible elastic mesh of interconnected fibers. Small-strain el astic properties of tissue are predicted using a finite-element method and an analytical method. The model can be used to estimate the compressibility of a very soft tissue based on its Young's modulus and extracellular volum e fraction.