Point-to-point registration of non-rigid medical images using local elastic transformation methods

Although a considerable amount of research has been devoted to the registration of medical images, a good proportion of this has been performed on rigid regions of the anatomy. This has tended to limit the practical value of such research. The registration of medical images which are non-rigid in nature is a seemingly difficult and not fully investigated problem. This paper presents an elastic transformation method which is used to perform matching of non-rigid medical images, that is, two-dimensional images of a region of the body such as the thorax or abdomen which exhibits a high level of elasticity. Some forms of elastic transformation may be more localized in scope than others, which leads to the categorization of elastic transformation methods into local and semi-local methods. This paper demonstrates the use of local elastic spatial transformations in matching non-rigid medical images. These transformations are illustrated by matching corresponding computed tomography and magnetic resonance images of the thorax.