Automatic hybrid registration for 2-dimensional CT abdominal images

Registration of abdominal images plays an important role in clinical practice, however, because of the complex deformations of organ structure and volume, abdominal image registration remains a challenge. In this paper, a hybrid registration approach is proposed, which consists of two procedures: intensity-based registration procedure and landmark-based registration procedure. In intensity-based registration, in order to speed up registration convergence and to improve registration computation efficiency, a wavelet-based hierarchical method is proposed, in which the global displacements are corrected using mutual information algorithm. In the landmark-based registration, firstly, the landmark points are selected automatically; and then, the local non-linear deformations are corrected using the elastically thin-plate splines. By combining the advantages of intensity-based registration method and that of landmark-based method, the proposed approach can register the images accurately and efficiently. The registration performance of the proposed algorithm is validated by experiments on clinical computed tomography (CT) abdominal images.