Computerized tomographic scanner having a toroidal x-ray tube with a stationary annular anode and a rotating cathode assembly

A CT scanner comprising:

• a toroidal x-ray tube defining a central bore of sufficient diameter for passing an imaged region of a subject therethrough, the x-ray tube including:
• a toroidal housing having an evacuated interior;
• an annular anode surface mounted within the toroidal housing interior, the anode surface being in thermal communication with a cooling fluid passage for circulating cooling fluid contiguous to the anode surface for removing heat;
• a cathode disposed within the toroidal housing for emitting electrons to form an electron beam that strikes the anode surface to generate an x-ray beam which passes across the central bore;
• a rotatable mounting means for rotatably mounting the cathode for rotation around the evacuated interior of the toroidal housing such that a location at which the electron beam strikes the anode surface is rotated through a ring of locations around the annular anode surface;
• a compensator mounted in the evacuated interior of the toroidal housing for rotation with the cathode and disposed adjacent the location at which the electron beam strikes the anode such that the generated x-ray beam passes therethrough;
• an x-ray tube mounting means for mounting the toroidal x-ray tube;
• a radiation detection means spanning at least an arc for detecting the x-ray beam after it is passed through the imaged subject region in the central bore;
• an x-ray beam apex location determining means for determining angular positions of the locations at which the electron beam strikes the anode surface;
• an image reconstruction means operatively connected with the radiation detection means and the x-ray beam apex location determining means for reconstructing an image representation of the image region of the subject.

A CT scanner comprising:

• a toroidal x-ray tube defining a central bore of sufficient diameter for receiving an image region of a subject therein, the x-ray tube including:
• a toroidal housing having an evacuated interior;
• an annular anode surface mounted within the toroidal housing interior, the anode surface being in thermal communication with a cooling fluid passage for circulating cooling fluid contiguous to the anode surface for removing heat;
• a high energy electron beam emitting means disposed within the toroidal housing for emitting a beam of electrons which strikes the anode surface and forms a higher energy x-ray beam;
• a low energy electron beam emitting means disposed within the toroidal housing for emitting an electron beam which strikes the anode surface and generates a lower energy x-ray beam, the higher and lower energy x-ray beams being directed across the central bore;
• a means for moving each of the electron beams to at least a multiplicity of points around the anode surface;
• an x-ray tube mounting means for mounting the toroidal x-ray tube;
• a radiation detection means spanning at least an arc for detecting at least one of the higher and lower energy x-ray beams after passing through the imaged subject region in the bore;
• an x-ray beam apex location determining means for determining angular positions at which the beams of electrons strike the anode surface;
• an image reconstruction means operatively connected with the radiation detection means and the x-ray beam apex location determining means for reconstructing at least one image representation of the image region of the subject.

A CT scanner comprising:

• a toroidal x-ray tube defining a central bore of sufficient diameter for passing an imaged region of a subject therethrough, the x-ray tube including:
• a toroidal housing having an evacuated interior;
• an annular anode surface mounted within the toroidal housing interior, the anode surface being in thermal communication with a cooling fluid passage for circulating cooling fluid contiguous to the anode surface for removing heat;
• a cathode disposed within the toroidal housing for emitting electrons to form an electron beam that strikes the anode surface to generate an x-ray beam which passes across the central bore;
• a rotatable mounting means for rotatably mounting the cathode around the evacuated interior of the toroidal housing such that a location at which the electron beam strikes the anode surface is rotated to a ring of locations around the annular anode surface;
• a plurality of voltage sources which are connected in parallel to apply a relatively high potential between the cathode and the anode surface, there being a sufficiently large plurality of voltage sources that if one of the voltage sources fails, a sum of the voltages of the remaining voltage sources provides sufficient electrical energy to continue generating the x-ray beam but at a reduced power;
• an x-ray tube mounting means for mounting the toroidal x-ray tube;
• a radiation detection means spanning at least an arc for detecting the x-ray beam after it is passed through the imaged subject region in the central bore;
• an x-ray beam apex location determining means for determining angular positions of the locations at which the electron beam strikes the anode surface;
• an image reconstruction means operatively connected with the radiation detection means and the x-ray beam apex location determining means for reconstructing an image representation of the image region of the subject.

A CT scanner comprising:

• a generally toroidal x-ray tube defining a central bore of sufficient diameter for passing an imaged region of a subject therethrough, the x-ray tube including:
• a toroidal housing having an evacuated interior, the housing defining an annular window facing toward a central axis of the central bore through which the x-ray beam passes;
• an annular anode surface mounted within the toroidal housing interior, the anode surface being in thermal communication with a cooling fluid passage for circulating cooling fluid contiguous to the anode surface for removing heat;
• a cathode assembly disposed within the toroidal housing including a means for emitting electrons to form an electron beam that strikes the anode surface to generate an x-ray beam that passes through the annular window and across the central bore;
• a means for moving the electron beam to at least a multiplicity of points around the anode surface;
• an annular shutter member which is disposable across the window for blocking the x-ray beam from passing therethrough;
• a means for selectively moving the shutter member into and out of the x-ray beam blocking relationship with the window;
• an x-ray tube mounting means for mounting the toroidal x-ray tube;
• an x-ray beam apex location determining means for determining an angular position at which the electron beam strikes the anode surface;
• a radiation detection means for detecting the x-ray beam after it is passed through the imaged subject region in the bore, the radiation detection means including:
• a ring of radiation detectors;
• a nutating means for selectively nutating a portion of the detector ring opposite the angular position in which the electron beam strikes the anode surface;
• an image reconstruction means operatively connected with the radiation detection means and the x-ray beam apex location determining means for reconstructing an image representation of the image region of the subject.

A CT scanner comprising:

• a toroidal x-ray tube defining a central bore of sufficient diameter for passing an imaged region of a subject therethrough, the x-ray tube including:
• a generally toroidal housing having an evacuated interior;
• an annular anode surface mounted within the toroidal housing interior, the anode surface being in thermal communication with a cooling fluid passage for circulating cooling fluid contiguous to the anode surface for removing heat;
• a cathode disposed within the toroidal housing for emitting electrons to form an electron beam that strikes the anode surface to generate an x-ray beam which passes across the central bore;
• a rotatable mounting means for rotatably mounting the cathode around the evacuated interior of the toroidal housing such that a location at which the electron beam strikes the anode surface is rotated to a ring of locations around the annular anode surface;
• an x-ray rube mounting means for mounting the toroidal x-ray tube;
• a radiation detection means spanning at least an arc for detecting the x-ray beam after it is passed through the imaged subject region in the central bore;
• a laser gyro for monitoring an angular position of the cathode;
• an image reconstruction means operatively connected with the radiation detection means and the laser gyro for reconstructing an image representation of the image region of the subject.

A CT scanner comprising:

• a toroidal x-ray tube defining a central bore of sufficient diameter for passage of an imaged region of a subject therethrough, the toroidal x-ray tube including:
• a toroidal housing defining an evacuated interior;
• an annular anode surface mounted within the toroidal housing interior and extending therearound;
• a cathode supporting means movably mounted in the evacuated interior of the toroidal x-ray tube;
• a rotating means for rotating the cathode supporting means around the evacuated interior of the toroidal housing;
• a cathode means for emitting a beam of electrons which strike the anode surface to generate an x-ray beam that is directed across the central bore, the cathode means being mounted to the cathode supporting means for rotation around the evacuated interior therewith such that the beam of electrons is rotated to strike the anode surface along a ring-shaped path such that the x-ray beam rotates around the central bore;
• a vacuum pumping means connected to the toroidal housing evacuated interior for actively maintaining the vacuum therein;
• a multiplicity of radiation detectors mounted along at least an arc segment for receiving the x-ray beam after the x-ray beam has traversed the central bore;
• a means for monitoring rotating of the cathode supporting means;
• an image reconstruction means operatively connected with the radiation detectors and the monitoring means for reconstructing an imaging representation of a region of a subject disposed within the central bore.

A CT scanner comprising:

• a toroidal x-ray tube housing extending around a central bore and having an evacuated interior;
• an annular anode surface mounted within the toroidal housing interior;
• a cathode means for emitting electrons to form a beam that strikes the anode surface, the cathode means being mounted on an annular ring within the toroidal housing interior;
• a rotating means for rotating the annular ring through the toroidal housing interior around the central bore;
• at least one voltage source for applying a sufficient voltage between the cathode means and the anode surface such that the beam of electrons strikes the anode surface with sufficient energy to generate an x-ray beam;
• at least one of a compensator and a collimator mounted to the annular ring for rotation therewith and adjacent to the cathode means such that the x-ray beam passes therethrough;
• an annular window defined in the toroidal housing through which the x-ray beam exits the housing and is directed toward a central axis of the bore;
• a shutter member which is selectively movable into and out of an x-ray blocking relationship with a window;
• a multiplicity of radiation detectors mounted along at least an arc segment for receiving the x-ray beam after the x-ray beam has traversed the central bore;
• a means for monitoring rotation of the annular ring;
• an image reconstruction means operatively connected with the radiation detectors and the rotation monitoring means for reconstructing an image representation of a region of a subject disposed within the central bore.

A CT scanner comprising:

• a toroidal x-ray tube defining a central bore of sufficient diameter for passage of an imaged region of a subject therethrough, the toroidal x-ray tube including:
• a toroidal housing defining an evacuated interior;
• an annular anode surface mounted within the toroidal housing interior and extending therearound;
• a cathode supporting means movably mounted in the evacuated interior of the toroidal x-ray tube;
• a rotating means for rotating the cathode supporting means around the evacuated interior of the toroidal housing;
• a cathode means for emitting a beam of electrons which strike the anode surface to generate an x-ray beam that is directed across the central bore, the cathode means being mounted to the cathode supporting means for rotation around the evacuated interior therewith such that the beam of electrons is rotated to strike the anode surface along a ring-shaped path such that the x-ray beam rotates around the central bore;
• a collimator mounted to the cathode supporting means and disposed closely adjacent to the anode surface adjacent a location at which the beam of electrons strikes the anode surface such that the x-ray beam passes therethrough and is collimated thereby, the collimator means rotating with the cathode supporting means and the cathode means such that the collimator means rotates with the x-ray beam;
• a multiplicity of radiation detectors mounted along at least an arc segment for receiving the x-ray beam after the x-ray beam has traversed the central bore;
• a means for monitoring rotating of the cathode supporting means;
• an image reconstruction means operatively connected with the radiation detectors and the monitoring means for reconstructing an imaging representation of a region of a subject disposed within the central bore.

A CT scanner comprising:

• a generally toroidal x-ray tube defining a central bore of sufficient diameter for receiving an imaged region of a subject therein, the x-ray tube including:
• a generally toroidal housing held to a substantially neutral potential, the toroidal housing having an evacuated interior;
• an anode surface mounted within the toroidal housing interior;
• a rotatable ring mounted in the evacuated interior of the toroidal housing, the ring being held substantially to the neutral potential;
• at least one cathode cup supported by the rotatable ring, the cathode cup emitting a beam of electrons which strikes the anode surface to generate an x-ray beam which crosses the central bore;
• an insulating means for insulating the cathode cup from the rotating ring;
• a means for rotating the ring within the evacuated interior of the toroidal housing;
• a means for maintaining the cathode cup at a large potential difference relative to the substantially neutral rotating ring, the substantially neutral toroidal housing, and the anode such that the large potential causes the electron beam from the cathode cup to strike the anode with sufficient energy to generate an x-ray beam, which x-ray beam traverses the central bore;
• a means for monitoring an angular position of the rotating ring;
• an x-ray detection means spanning at least an arc for detecting the x-ray beam after it has traversed the central bore;
• an image reconstruction means operatively connected with the radiation means and the position detecting means for reconstructing an image representation of a portion of the subject in the central bore.