Interactive Model-based Image Registration
We present an interactive technique for the registration of captured images of elastic and rigid body parts in which the user is given ﬂexible control over material speciﬁc deformation properties. Our method can effectively handle arbitrary stiffness distributions and it achieves an accurate matching without sacriﬁcing the physical correctness of the simulated deformations. The algorithm consists of three steps, which are performed iteratively until an optimal spatial mapping is determined: First, the optical ﬂow is used to predict an initial image transformation. Second, a priori knowledge of the deformation model is used to reﬁne the predicted ﬁeld. A physics-based ﬁlter operation generates a transformation that is consistent with the model of linear elasticity. Third, the process is repeated using the displaced template image. To achieve accurate image deformations we employ implicit multigrid solvers using ﬁnite differences (optical ﬂow) and ﬁnite elements (linear elasticity). The robustness and accuracy of our method is validated using synthetic and real clinical data composed of heterogeneous materials exhibiting different stiffness characteristics.