Simulation-Based Joint Estimation of Body Deformation and Elasticity Parameters

Physically-based elastic body simulation has been applied to medical image registration to enforce physical constraints, since each organ in the image can be viewed as an elastic body. However, it requires hand adjustment for the material properties to achieve the desired output shape, and the boundary conditions (forces or displacements on boundary nodes) cannot be acquired directly from the images. We present a general method for estimating these parameters for a simulator automatically using an iterative optimization framework, given the desired (target) output surface. During the optimization, the input model is deformed by the simulator, and an objective function based on the distance between the deformed surface and the target surface is minimized numerically. The optimization framework does not depend on a particular simulation method and is therefore suitable for different physical models. Besides matching the surface boundaries, our method guarantees the quality of the deformation fields, as they are computed using a physics-based simulation. Compared to other FEM-based methods, our technique can determine the elastic properties automatically and does not rely on explicit surface matching for generating boundary conditions.