1. A method for updating a 2D/3D registration between a three-dimensional image data set corresponding to a target area and a plurality of two-dimensional projection images of the target area, the target area being subjected to a movement, the method comprising: selecting a plurality of contour points along a contour associated with a rigid object in the target area, the contour being visible in a first projection image and a three-dimensional image data set registered therewith; determining a displacement of each contour point of the plurality of contour points between the first projection image and a successively captured second projection image; obtaining movement information for each contour point of the plurality of contour points based on the determined displacement, the movement information describing a movement of the rigid object; and updating the registration based on the obtained movement information; wherein the obtaining of the movement information comprises: restricting degrees of freedom of movement to observable movements that are perpendicular to a course of the contour in the three-dimensional image data set; and solving a system of equations for a three-dimensional target plane that comprises the displaced contour point.