1. A computed tomography method for forming images of an object to be examined which is arranged in an examination zone, which method includes the steps of: generating, while using an X-ray source, a conical X-ray beam which traverses the examination zone or the object to be examined which is arranged therein, rotating the X-ray source and an oppositely arranged X-ray detector on the other side of the examination zone along a trajectory around the examination zone, acquiring projection data by means of the X-ray detector during the rotation, reconstructing one or more images from the projection data, characterized in that the method also includes the steps of: a) selecting an imaging zone of the object to be examined, b) determining the sub-regions of the X-ray detector on which the imaging zone of the object to be examined is projected during the acquisition of the projection data, c) forming sub-projection data by selecting the projection data associated with the subregions from the acquired projection data, and d) reconstructing the desired image from the sub-projection data by backprojection.