A Study of Interdependence between Vessel Enhancement and Registration for Lung 4D-CT

In this work we present a novel study which considers the mutual effect of registration and vessel enhancement for the case of lung 4D-CT registration. Our work is based upon popular and well established approaches for registration viz. Diffeomorphic Demons approach, and vessel enhancement via the vesselness filter. We experimentally analyze and demonstrate that the registration across temporal 3D volumes can benefit if carried out in the vesselness domain, more so as the temporal spacing between the volumes increases. With respect to vessel enhancement, we propose an extension of the 3D vesselness filter to 4D, and our experiments indicate that vessel enhancement in 4D can be beneficial than that in 3D. Moreover, a 4D vesselness filter allows us to consider the effect of registration via vessel enhancement process. Based on this observation, we also demonstrate that 4D vesselness computation with registration of nearby 3D volumes can further improve upon that without registration. Our proposed methods and studies can help in improving the registration and vessel enhancement especially for lung 4D CT, which benefits from both.