X-ray tube for computer tomography

A method for operating an x-ray tube in a computer tomography system comprising the steps of:

• in an x-ray tube, generating an electron beam and directing said electron beam to a rotating anode having an anode surface with an incident area on which said electron beam is incident on a focal spot to cause the generation of x-rays, said anode surface having a circumferential direction;
• directing said x-rays onto a radiation detector with an examination subject disposed between said x-ray tube and said radiation detector and generating output signals from said detector corresponding to the radiation incident on said detector;
• moving said x-ray tube and said radiation detector through a plurality of successive scanning positions relative to said examination subject;
• sampling said output signals in said plurality of successive scanning positions;
• and
• periodically radially deflecting said electron beam in a deflection direction intersecting said circumferential direction for moving said focal spot radially on said anode surface from an initial position to a final position once per scanning position.

An x-ray tube comprising:

• an evacuated housing:
• cathode means in said housing for generating an electron beam;
• a rotary anode disposed in said housing and having an anode surface with an incident area on which said electron beam is incident on a focal spot to cause the generation of x-rays, said anode surface having a circumferential direction and said incident area having dimensions and a geometrical shape;
• means for rotating said rotary anode at a rotary frequency;
• deflection means for interacting with said electron beam for deflecting said electron beam;
• and
• control means for operating said deflection means for generating a deflection signal supplied to said deflection means for deflecting said electron beam in a deflection motion having a deflection path along said deflection direction, said means for generating said deflection signal generating said deflection signal dependent on said deflection direction and path, said rotary frequency, said dimensions and geometrical shape of said incident area, a distance traversed by said focal spot between said final position and said initial position measured transversely relative to said circumferential direction, and the extent of said focal spot in said circumferential direction and in a direction transversely relative to said circumferential direction, for causing said focal spot to successively sweep respective regions of said incident area as said focal spot moves from said initial position to said final position which are disposed in maximally close proximity to each other without overlapping.