MRE quantitatively determines the stiffness of biological tissues by measuring its mechanical response to an external stress.[1] Specifically, MRE calculates the shear modulus of a tissue from its shear-wave displacement measurements.[2] The elastic modulus quantifies the stiffness of a material, or how well it resists elastic deformation as a force is applied. For elastic materials, strain is directly proportional to stress within an elastic region. The elastic modulus is seen as the proportionality constant between stress and strain within this region.