Multiscale deformable registration using edge preserving scale space for adaptive radiation therapy

Registration of planning images with daily images is an important component for adaptive radiation therapy (ART). In this paper, a multiscale deformable registration framework is proposed by combining edge preserving scale space with the free form deformation (FFD) for registration of planning computed tomography (CT) images with daily cone beam CT (CBCT) images. The edge preserving scale space which is able to select edges and contours of an image according to their geometric size is derived from the total variation model with the L1 norm (TV-L1). At each scale, the selected edges and contours are sufficiently strong to drive the deformation using the FFD grid, then the deformation fields are gained by a coarse to fine manner. Furthermore, for automated registration we design an optimal estimation of the TV-L1 parameter by minimizing the defined offset. The experiments on CT and CBCT images show accuracy and robustness when compared to traditional methods.