US 5,475,729 A · X-ray reference channel and x-ray control circuit for ring tube CT scanners

Abstract

A toroidal x-ray tube (I) is supported and selectively positioned by a gantry (II). The x-ray tube includes a toroidal housing (A) in which a rotor (30) is rotatably mounted. One or more cathodes (C) are mounted on the rotor for generating an electron beam which strikes an anode (B) to generate a beam of x-rays which passes through a window (20) and strikes an annular ring of detectors (160). A grid bias control circuit (100) selectively applies a continuously adjustable bias to a grid (36) for regulating the electron current, hence the intensity of the x-ray beam. A scintillating optical fiber (110) extends around the exterior of the window. The scintillation optical fiber includes fluorescent dopant (116) which convert a very small fraction of the x-rays into optical light which is transmitted along the fibers to an opto-electric transducer (118). The opto-electric transducer is connected with the grid bias control circuit. The opto-electrical transducer (118) can also be connected with an intensity compensator (162) for adjusting the signals from the detector ring before they are reconstructed (164 ) into an image representation.

Claims25

Dependent claims

An x-ray tube comprising:

a generally toroidal housing having an evacuated interior and an annular x-ray transmissive window;
an annular anode mounted in the toroidal housing interior, the anode being in thermal communication with a circulated cooling fluid passage such that the cooling fluid removes heat from the anode;
a rotor rotatably disposed within an interior of the toroidal housing;
a plurality of cathode assemblies, each the cathode assembly selectively emitting electrons to form an electron beam that strikes the anode to generate an x-ray beam, the cathode assemblies being mounted to the rotor such that the electron beams rotate around the annular anode as the rotor rotates;
a cathode assembly electrical power transfer circuit for transferring cathode assembly electrical power of a selectable frequency from the housing to the rotor;
a plurality of bandpass circuits each having a different bandpass frequency, each of the bandpass circuits being connected between the cathode assembly electrical power transfer circuit and one of the cathode assemblies such that a one of the cathode assemblies to receive electrical power is selected by the frequency of the transferred electrical power.

3 more elements

A CT scanner comprising:

a patient support for supporting a selected portion of a patient in an examination region;
an x-ray ring tube including:
a generally toroidal housing having an evacuated interior and an annular x-ray transmissive window;
an annular anode mounted in the toroidal housing interior, the anode being in thermal communication with a circulated cooling fluid passage such that the cooling fluid removes heat from the anode;
a rotor disposed within an interior of the toroidal housing;
at least one cathode assembly mounted to the rotor for rotation therewith, the cathode assembly including an electron source which emits an electron beam that strikes the anode to generate an x-ray beam;
the rotor being rotatably disposed in the housing such that electron beam is rotated around the anode;
a scintillation optical fiber mounted adjacent the window such that x-rays exiting the window pass through the scintillating optical fiber, the scintillating optical fiber converting a small amount of incident x-rays to optical light and transmitting the light therealong;
an opto-electric transducer which converts the light from the scintillating optical fiber into an x-ray intensity signal;
a gantry which supports and selectively positions the x-ray ring tube around the examination region;
a ring of radiation detectors for receiving x-rays from the window which have traversed the examination region;
an image reconstruction processor for reconstructing the signals from the ring of radiation detectors into image representations.

9 more elements

A CT scanner comprising:

a patient support for supporting a selected portion of a patient in an examination region;
an x-ray ring tube including:
a generally toroidal housing having an evacuated interior and an annular x-ray transmissive window;
an annular anode mounted in the toroidal housing interior, the anode being in thermal communication with a circulated cooling fluid passage such that the cooling fluid removes heat from the anode;
a rotor rotatably disposed within an interior of the toroidal housing;
at least one cathode assembly mounted to the rotor for rotation therewith, the cathode assembly including a means for emitting electrons to form an electron beam that strikes the anode to generate an x-ray beam;
a transformer for supplying electrical power to the cathode assembly, the transformer including an annular winding extending around and mounted to the rotor for rotation therewith and a U-shaped winding mounted to the housing and receiving the annular winding therethrough;
a means for rotating the annular rotor such that electron beam is rotated around the anode and such that the annular winding moves through the U-shaped winding;
a radiation intensity monitoring means mounted adjacent the window such that x-rays exiting the window pass through the radiation intensity monitoring means;
a gantry which supports and selectively positions the x-ray ring tube around the examination region;
a ring of radiation detectors for receiving x-rays from the window which have traversed the examination region;
an image reconstruction means for reconstructing signals from the ring of radiation detectors into image representations.

9 more elements

A CT scanner comprising:

a patient support for supporting a selected portion of a patient in an examination region;
an x-ray ring tube including:
a generally toroidal housing having an evacuated interior and an annular x-ray transmissive window;
an annular anode mounted in the toroidal housing interior, the anode being in thermal communication with a circulated cooling fluid passage such that the cooling fluid removes heat from the anode;
a rotor rotatably disposed within an interior of the toroidal housing;
at least one cathode assembly mounted to the rotor for rotation therewith, the cathode assembly including an electron emitting source which forms an electron beam that strikes the anode to generate an x-ray beam such that electron beam is rotated around the anode;
a voltage biasing means for creating a bias voltage field between the cathode assembly and the anode such that the electron beam passes therethrough;
a bias adjusting circuit for adjustably modulating the bias voltage field over a multiplicity of field strengths for adjustably controlling an intensity of the generated x-ray beam over a multiplicity of x-ray beam intensities;
a gantry which supports and selectively positions the x-ray ring tube around the examination region;
a ring of radiation detectors for receiving radiation from the x-ray ring tube which have traversed the examination region;
an image reconstruction processor which reconstructs signals from the radiation detector ring into image representations.

8 more elements

Dependencies are inferred from the claim text.

X-ray reference channel and x-ray control circuit for ring tube CT scanners

Life of this patent

X-ray reference channel and x-ray control circuit for ring tube CT scanners

Life of this patent

Abstract

Claims25