The present invention relates to medical radiography, in which individual images of an object are taken at different projection angles and a 3D image subsequently synthesized from this image information. The object to be imaged is arranged locked in an object positioning means and during the imaging process, the x-ray source is continuously moved with respect to location of the object. During the continuous movement of the x-ray source there are irradiation periods and non-irradiation periods and during an irradiation period, the object positioning means is moved as synchronized with the movement of the x-ray source so as to follow the movement of the x-ray source.