A method of obtaining a 3D image of a part of a patient's body is disclosed, based on a fraction image having a limited field-of-view and complementing this with information from a planning image having a greater field-of-view. In the area outside of the fraction image field-of-view, contour and anatomical data from the planning image are used to complement the fraction image, by means of a contour-guided deformable registration between the planning image and the fraction image.
