Exploiting strain-hardening of tissue to increase contrast in elasticity imaging

Most biological tissues show strain hardening. For example, direct mechanical measurements on human prostate show up to a threefold increase in Young's modulus over a 10% deformation. In addition, strain-hardening behavior differs significantly between tissue types. In conventional elasticity imaging these effects produce strain dependent elastic contrast. Furthermore, image quality is suboptimal because softer tissues are imaged at higher strains than stiffer tissues. By applying linear processing on many small subsets over a large total deformation, strain-hardening behavior was measured for an agar-gel based phantom. Such processing can address strain-hardening problems in conventional elasticity imaging, and produce images of the elastic nonlinearity itself. Finally preliminary results for human prostate are presented.