Poroelastography: Estimating and Imaging the Poroelastic Properties of Tissues

In the field of elastography [l], biological tissues are typically assumed to be purely linear elastic solids. However, several tissues including been known to be poroelastic. We recently developed brain, cartilage and edematous soft tissues, have long a method to estimate the local Poisson's ratio in linear elastic solids [2]. In the current study we use the same method to measure the time-dependent effective Poisson's ratio in poroelastic materials. The resulting distribution of the fluid within the solid at each time time-sequenced poroelastograms show the spatial solid and its permeability to the fluid. Results were instant and give insight into the Poisson's ratio of the obtained from both finite-element simulations and experimental poroelastic phantoms. INTRODUCTION A poroelastic, or porous elastic, material is a material saturated with a fluid that flows relative to the deforming solid matrix. Armstrong et al. [3] have shown analytically that during unconfined stress relaxation of a poroelastic material, i.e., application of a constant applied strain over time (Fig. I), the ratio of lateral-to-axial strain, or efecfive Poisson's ratio ( vef ) changes with time and is asymptotically equal to the Poisson's ratio of the solid (v, ), or