Dual filament, electrostatically controlled focal spot for x-ray tubes

An x-ray tube comprising:

• a cathode assembly having:
• a long filament portion and a short filament portion;
• a common electrostatic deflection electrode disposed between the long and short filament portions;
• a first electrostatic deflection electrode disposed adjacent the long filament portion opposite the common electrode;
• a second electrostatic deflection electrode disposed adjacent the short filament portion opposite the common electrode;
• an anode;
• and
• a vacuum enclosure enclosing the cathode assembly and the anode.

An x-ray tube with an adjustable length and width focal spot comprising:

• an anode;
• a cathode assembly including at least two filament segments and electrostatic deflection electrodes;
• a vacuum envelope surrounding the cathode assembly and the anode;
• not more than four leads passing through the vacuum envelope to supply electrical power to the filament sections and bias potentials to the electrodes;
• and
• a filament selection circuit disposed inside the vacuum envelope in connection with the four leads passing through the vacuum envelope, the filament selection circuit being connected with the filament segments for applying electric current selectively through a long section of filament and a short section of filament for controlling focal spot length and being connected with the electrodes for selecting focal spot width and position.

A computerized tomographic (CT) system comprising:

• an x-ray tube having an adjustable length and width focal spot for transmitting radiation through a subject disposed in a subject receiving aperture, said x-ray tube comprising:
• an anode;
• a cathode assembly including at least two filament segments and electrostatic deflection electrodes;
• a vacuum envelope surrounding the cathode assembly and the anode;
• not more than four leads passing through the vacuum envelope to supply electrical power to the filament sections and bias potentials to the electrodes;
• and
• a filament selection circuit disposed inside the vacuum envelope in connection with the four leads passing through the vacuum envelope, the filament selection circuit being connected with the filament segments for applying electric current selectively through a long section of filament and a short section of filament for controlling focal spot length and being connected with the electrodes for selecting focal spot width and position;
• detector means coupled to the x-ray tube for detecting radiation emitted from the x-ray tube after passage of the radiation through the subject;
• a rotatable gantry on which the x-ray tube and detector means are mounted;
• and,
• means for processing the detected radiation into a tomographic image representation.

A computerized tomographic system comprising:

• a source of penetrating radiation for transmitting radiation through a subject disposed in a subject receiving aperture, said source of penetrating radiation including:
• an evacuated envelope;
• an anode disposed at a first end of the evacuated envelope;
• a cathode assembly disposed at a second end of the evacuated envelope, said cathode assembly comprising:
• a cathode base portion;
• at least a first filament and a second filament, where the first filament is longer than the second filament;
• and
• at least three deflection electrodes being attached to and electrically insulated from the cathode base portion;
• and,
• means for individually and selectively applying potentials to different ones of the deflection electrodes;
• detector means coupled to the source for detecting radiation emitted from the source after passage of the radiation through the subject;
• a rotatable gantry on which the source and detector means are mounted;
• and,
• means for processing the detected radiation into a tomographic image representation.

A computerized tomographic (CT) system comprising:

• a source of penetrating radiation for transmitting radiation through a subject disposed in a subject receiving aperture, said source of penetrating radiation including:
• an evacuated envelope;
• an anode disposed at a first end of the evacuated envelope;
• a cathode assembly disposed at a second end of the evacuated envelope, said cathode assembly comprising:
• at least a first filament and a second filament, where the first filament is longer than the second filament;
• and
• a cathode cup which is subdivided into a plurality of parts, said plurality of parts being electrically insulated from each other;
• and
• means for individually and selectively applying potentials to different ones of the parts of the cathode cup;
• detector means coupled to the source for detecting radiation emitted from the source after passage of the radiation through the subject;
• a rotatable gantry on which the source and detector means are mounted;
• and,
• means for processing the detected radiation into a tomographic image representation.