Radiation therapy of cancer necessitates accurate tumour targeting. Unfortunately, during the treatment the tumour and the related organs can undergo large displacement and deformation. Physicians need an estimation of these movements, for an adapted therapy. In this paper, we propose a methodology to provide physicians with reconstructed 4D (3D+time) CT scans, considered as essential data. Moreover we propose an interactive visualisation tool, permitting the exploration of reconstructed 4D CT scans as well as the generation of new CT scan sections in any direction of the 3D space.