Off-focal radiation limiting precollimator and adjustable ring collimator for x-ray CT scanners

An x-ray tube comprising:

• a generally toroidal housing having an evacuated annular interior;
• an annular anode mounted in the toroidal housing interior;
• a rotating frame rotatably disposed within the toroidal housing interior;
• at least one cathode assembly mounted to the frame for rotation therewith, the cathode assembly including an electron source forming an electron beam that strikes the anode to generate an x-ray beam;
• a precollimator supported in the toroidal housing interior having an x-ray passing slot, the pre-collimator being mounted on the rotating frame in alignment with at least one cathode assembly;
• and,
• a collimator for collimating the x-ray beam passing through the precollimator slot.

An x-ray tube comprising:

• a generally toroidal housing having an evacuated annular interior;
• an annular anode mounted in the toroidal housing interior;
• a rotating frame rotatably disposed within the toroidal housing interior;
• at least one cathode assembly mounted to the frame for rotation therewith, the cathode assembly including an electron source forming an electron beam that strikes the anode to generate an x-ray beam;
• a pre-collimator supported by the anode in the toroidal housing interior and having an x-ray passing slot;
• and,
• a collimator for collimating the x-ray beam passed through the precollimator slot.

An x-ray tube comprising:

• a generally toroidal housing having an evacuated annular interior;
• an annular anode mounted in the toroidal housing interior;
• a rotating frame rotatably disposed within the toroidal housing interior;
• at least one cathode assembly mounted to the frame for rotation therewith, the cathode assembly including an electron source forming an electron beam that strikes the anode to generate an x-ray beam;
• a precollimator supported in the toroidal housing interior having an x-ray passing slot;
• a shield ring attached around the anode on a side opposite the pre-collimator;
• and,
• a collimator for collimating the x-ray beam passed through the precollimator slot.

An x-ray tube comprising:

• a generally toroidal housing having an evacuated, annular interior;
• an annular anode mounted in the toroidal housing interior;
• a rotating frame rotatably disposed within the toroidal housing interior;
• at least one cathode assembly mounted to the rotating frame for rotation therewith, the cathode assembly including an electron source forming an electron beam that strikes the anode to generate x-rays;
• a ring collimator supported by toroidal housing for collimating the x-rays into a beam, the collimator including a first ring and a second ring between which the x-ray beam is defined, the first and second rings having a common central axis, at least one of the first and second rings being adjustably mounted such that a distance between the first and second rings is adjustable, the first ring having a first diameter and the second ring having a second diameter, the first diameter being greater than the second diameter.

An x-ray tube comprising:

• a generally toroidal housing having an evacuated, annular interior;
• an annular anode mounted in the toroidal housing interior;
• a rotating frame rotatably disposed within the toroidal housing interior;
• at least one cathode assembly mounted to the rotating frame for rotation therewith, the cathode assembly including an electron source forming an electron beam that strikes the anode to generate x-rays;
• a pre-collimator supported in the evacuated, annular interior of the toroidal housing, the precollimator having an x-ray passing slot disposed between the annular anode and the central axis such that x-rays pass through the precollimator prior to exiting the toroidal housing;
• a ring collimator supported by toroidal housing for collimating the x-rays which passed through the precollimator slot into a beam, the collimator including a first ring and a second ring between which the x-ray beam is defined, the first and second rings having a common central axis, at least one of the first and second rings being adjustably mounted such that a distance between the first and second rings is adjustable.

An x-ray tube comprising:

• a generally toroidal housing having an evacuated, annular interior;
• an annular anode mounted in the toroidal housing interior;
• a rotating frame rotatably disposed within tho toroidal housing interior;
• at least one cathode assembly mounted to the rotating frame for rotation therewith, the cathode assembly including an electron source forming an electron beam that strikes the anode to generate x-rays;
• a ring collimator supported by toroidal housing for collimating the x-rays into a collimated x-ray beam centered on a central axis, the collimator including a first ring and a second ring between which the x-ray beam is defined, the first and second rings having a common central axis, at least one of the first and second rings being adjustably mounted such that a distance between the first and second rings is adjustable;
• and
• a means for controlling the first and second rings to adjust a width of the collimated x-ray beam by a selectively adjustable width and to translate the central axis of the collimated x-ray beam one-half of the selected width.

An CT scanner comprising:

• a patient support for supporting a selected portion of a patient in an examination region;
• an x-ray tube including:
• a generally toroidal housing having an evacuated interior;
• an annular anode mounted in the interior;
• a rotating frame rotatably disposed within the interior;
• at least one cathode assembly mounted to the frame for rotation therewith, the cathode assembly including an electron source forming an electron beam that strikes the anode to generate an x-ray beam;
• a precollimator mounted in a fixed relationship to the anode in the evacuated interior for limiting a cross-section dimension of the x-ray beam subsequent to generation thereof;
• and,
• a collimator for collimating the x-ray beam of limited cross-sectional dimension from the precollimator.

A CT scanner comprising:

• a patient support for supporting a selected portion of a patient in an examination region;
• an x-ray tube including:
• a generally toroidal housing having an evacuated interior and extending around a central axis;
• an annular anode mounted in the interior;
• a rotating frame rotatably disposed within the evacuated interior;
• at least one cathode assembly mounted to the rotating frame for rotation therewith, the cathode assembly including an electron source forming an electron beam that strikes the anode along a circular path to generate x-rays, the circular path defining a first plane orthogonal to the central axis;
• an annular x-ray window mounted in the housing facing toward the central axis through which the x-rays are passed;
• a ring of x-ray detectors extending around the toroidal housing adjacent and axially offset from the annular x-ray window, the x-ray detectors defining a second plane that is parallel to and displaced from the first plane;
• a precollimator supported within the toroidal housing evacuated interior between the annular anode and the annular window;
• a ring collimator including a first ring and a second ring, the first and second rings being disposed on opposing sides of the annular window, the ring collimator and the precollimator interacting to define an x-ray beam that originates at the anode in the first plane, crosses the central axis, and intersects the detectors at the second plane.

An x-ray tube comprising:

• an evacuated housing;
• an anode assembly disposed in the evacuated housing, the anode assembly having an annular anode track therearound;
• a cathode assembly mounted in the evacuated housing for forming a beam of electrons that strike the anode track to generate x-rays;
• and,
• a ring of x-ray blocking material mounted to the anode and extending around the anode track.