A recording unit is rotatable about an axis of rotation, and includes an X-ray emitter and detector to detect X-rays from a fan-shaped region. The fan-shaped region is asymmetrical in relation to a vertical to the axis of rotation, running through the X-ray detector wherein the two edges of the fan-shaped region, on rotation, in each case tangentially delimit a first projection region and a second projection region. The second projection region abuts the first projection region. A method includes recording projections of the two projection regions during a full rotation of the recording unit for the reconstruction of a first image of the first projection region in such a way that the projection angle intervals in each case exhibit the same start angle. It further includes reconstructing a second image of the second projection region to merge the two reconstructed projection regions to form one unitary image.