X-ray beam-shaping filter and X-ray imaging machine incorporating such a filter

An imaging machine comprising a source of beam radiation, a shaping filter disposed in the beam and means for collecting the radiation and forming an image wherein the shaping filter comprises a main frame in the form of a flat ring provided with a central circular opening for passage of a beam of radiation, at least one sliding rail fixed to one of the main surfaces of the main frame and at least one compensating plate made of a radiation-absorbent material, which can be moved along the rail between a retracted position in which the compensating plate lies outside a maximum field of view of the beam and active positions in which the compensating plate lies at least partly within the maximum field of view of the beam wherein the compensating plate comprises a first and second plate element which can be moved one relative to the other in such a way that, when the plate is in an active position, the thickness of absorbent material through which the beam passes is constant.