1. A method for acquiring a series of two-dimensional X-ray attenuation data of an object under examination that includes a region of interest by means of an X-ray imaging apparatus having an X-ray scanning unit, the method comprising the steps of positioning the object under examination to a first position, wherein the first position places the object such that a center of the object is off-set from an iso-center of the X-ray imaging apparatus and the region of interest is aligned with the iso-center of the X-ray imaging apparatus, rotating the X-ray scanning unit around a rotational axis such that the object under examination is scanned under different projection angles, and moving the object in a direction transverse to the rotational axis, to a second position, wherein the movement of the object is coupled to the rotation of the X-ray scanning unit and wherein the second position places the object such that the region of interest is not aligned with the iso-center of the X-ray imaging apparatus.