1. A method for acquiring a series of two-dimensional X-ray attenuation data of an object under examination ( 110 , 310 ) by means of an X-ray imaging apparatus ( 100 ) having an X-ray scanning unit ( 101 , 310 ), the method comprising the steps of rotating the X-ray scanning unit ( 101 , 301 ) around a rotational axis such that the object under examination ( 110 , 310 ) is scanned under different projection angles, and moving the object under examination ( 110 , 310 ) relative to the rotational axis, wherein the movement of the object under examination ( 110 , 310 ) is coupled to the rotation of the X-ray scanning unit ( 101 , 301 ).