The spatio-temporal strain distribution in inhomogeneous poroelastic phantoms

The presence of a mobile fluid in a porous tissue modifies aspects of the tissue´s mechanical behaviour such as the time variation of strain induced by a sustained compression. Elastography can be used to follow such responses and to estimate poroelastic parameters. This preliminary study examined axial strain variation in a poroelastic cylinder embedded in a quasi-elastic (or weakly permeable) background. Finite element analysis and experiment were compared. Unlike the case of purely elastic materials a region with high strain decaying with time was observed at the interface between the cylinder and the background. The time variation of strain in different regions of the phantom showed known poroelastic behaviour in that, as fluid was expelled, some regions contracted axially while others expanded axially. The strain relaxation time varied in a systematic manner in the different materials.