A CT scanning apparatus includes a control apparatus arranged to cause a first rotation of a gantry and trigger an x-ray source to emit x-radiation at a first x-ray energy when an angular encoder reports that the gantry is at each of multiple predetermined angular locations, and cause a second rotation of the gantry and trigger the x-ray source to emit x-radiation at a second x-ray energy differing from the first x-ray energy when the angular encoder reports that the gantry is at each of the same predetermined angular locations. An image processing means receives the projection images and reconstructs them into a volumetric image. A support couch is provided for the patient, and to minimize the likelihood of movement artifacts, the support couch includes a patient immobilisation system such as an evacuatable bead bag, bite post, or stereotactic frames, or the like.
