Elastography based on mechanical and image energy minimization

摘要

Ultrasound elastography (UE) is a promising imaging modality [1]. In vascular applications it uses ultrasound images of arteries in motion to assess their mechanical parameters and stress distributions in physiological or interventional loading conditions [2]. However some simplifying assumptions adopted classically in UE image processing methods restrict this modality to strain imaging.This work presents a new UE image processing method based on differential optical flow. The method constrains the solution of the optical flow problem to minimize a mechanical potential energy. In other words, from all possible solutions of the optical flow problem, it determines the one that minimizes strain energy density of the tissue.In addition, in order to estimate concurrently the stiffness parameter of the tissue with its optical flow (or apparent displacement field); we constrain them to verify the tissue mechanical equilibrium equations.In principle, with this approach we can assess the strain field and map the stiffness parameter for an elastic tissue.Finally our approach also allows us to estimate mechanical parameters of strained phantoms, from their RF or B-mode ultrasound images, considering not only the usual linear elastic mechanical law but also hyperelastic ones.