Local motion analysis in 4D lung CT using fast groupwise registration

Automatic tools for the propagation of contours and surfaces in time series of CT images (4DCT) are necessary e.g. for dose calculation in radio-therapy-planning. The state of the art method is the registration of 3-D frames of the sequence on a static reference volume or the registration of consecutive volume pairs. Based on the computed vector fields, the contours and surfaces are then propagated through the entire 4-D series. However, the registrations frequently suffer from common image or gating artefacts in the time series. To overcome the problem, we propose a groupwise 4-D registration approach combined with a motion model to perform the registration of a sequence of images.