Strain Measurement Using Deformable Image Registration

The accurate determination of strain in deforming biological tissues is a necessary and important part of experimental investigations in biomechanics. We have developed a method, referred to as Hyperelastic Warping, to combine medical image data with a solid mechanics analysis approach to allow estimation of tissue strains in the absence of detailed information about boundary conditions and in some cases constitutive information. The method makes use of medical image data to provide information about the deforming tissue and thus the strain and stress fields. The mathematical problem is to search through all admissible configurations for the one that minimizes the difference between a transformed template image and a target image collected experimentally. The resulting deformation map is used to determine the strain field. This technique has been applied successfully to determine strain in several biological soft tissues. This paper describes the theory, implementation and validation of the technique for measurement of transmural strains in the left ventricle.