Exploring the nonlinear elastic behavior of phantoms materials for elastography

Most tissues present nonlinear stress/strain relationship for strains larger than 5%. Recently, strain images for compressions beyond this amount have been reported. To achieve a better comprehension of the tissues nonlinear parameters being analyzed from these images, the nonlinear stress/strain properties of phantom materials must be better understood. The hyperelastic nonlinear behavior of such materials was analyzed. The stress/strain curves for four sets of samples (plain gelatin; plain agar; agar/gelatin mixtures; oil in agar/gelatin mixtures) were fit to the Verona-Westmann nonlinear model. The elasticity of plain agar was more nonlinear than that of gelatin. The agar/gelatin mixtures showed a nonlinear behavior between that of gelatin and agar. It was observed that adding oil to the agar/gelatin mixtures decreased the stiffness of the gels in addition to decreasing their nonlinear behavior.