Fig. 2.

Flow chart of deformable image registration process. The similarity index is calculated with given a fixed image and a moving image. The optimization algorithm tries to maximize the similarity index by changing deformation vector field (DVF) and the moving image is deformed based on the DVF. The similarity index is recalculated with the deformed moving image and the fixed image. This optimization process is done iteratively until the improvement of the similarity index reaches its target.