1. A computer tomography method comprising: generating a first cone beam using a beam source which passes through a scan region, or an object located in the scan region, during a helical relative movement between the beam source, and the scan region or object, comprising a rotation about a rotation axis and a displacement parallel to the rotation axis; acquiring a first set of measurement values using a detector unit during the relative movement, which depend on the intensity in the first cone beam on another side of the scan region; reconstructing a first CT image from the first set of measurement values; generating a second cone beam using the beam source which passes through the scan region, or the object, in conjunction with a circular relative movement between the beam source and the scan region or object, at a position of the scan region which the first cone beam has already crossed during the helical relative movement; acquiring a second set of measurement values using the detector unit during the circular relative movement; and iteratively reconstructing a second CT image from the second set of measurement values by correcting an approximation image derived from the first CT image in each iteration cycle by comparing projection values calculated from the approximation image with the second set of measurement values.