Evaluation of image registration for measuring deformation fields in soft tissue mechanics

High‐fidelity biomechanical models usually involve the mechanical characterisation of biological tissues using experimental methods based on optical measurements. In most experiments, strains are evaluated based on displacements of a few markers and represents an average within the region of interest (ROI). Full‐field measurements may improve description of non‐homogeneous materials such as soft tissues. The approach based on non‐rigid image registration is proposed and compared with standard digital image correlation (DIC) on a set of samples, including (i) complex heterogeneous deformations with sub‐pixel displacement, (ii) a typical uniaxial tension test of aorta, and (iii) an indentation test on skin. The possibility to extend the ROI to the whole sample and the exploitation of a natural tissue pattern represents the main assets of the proposed method whereas the results show similar accuracy as standard DIC when analysing sub‐pixel deformations. Therefore, displacement and strain fields measurement based on image registration is very promising to characterise heterogeneous specimens with irregular shapes and/or small dimensions, which are typical features of soft biological tissues.