US 5,179,583 AGranted

X-ray tube for CT apparatus

AssigneeShimadzu Corporation

InventorShiro Oikawa

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Abstract

An X-ray tube for a CT apparatus comprises a ring-shaped vacuum tube containing a fixed cathode having a thermion emitting surface, a ring-shaped fixed anode, and a ring-shaped rotatable cathode interposed between the fixed cathode and fixed anode. The rotatable cathode defines a thermion receiving surface opposed to the thermion emitting surface, and a thermion emitting portion opposed to the fixed anode. Thermions are emitted from the thermion emitting portion toward the fixed anode while the rotatable cathode is suspended to non-contact state and rotated at high speed. With the thermions being accelerated and colliding on the fixed anode, an X-ray is generated toward the center of the vacuum tube. The X-ray generating position moves at high speed along a circumferential surface of the fixed anode with rotation of the rotatable cathode.

Claims9

Dependent claims

An X-ray tube for a CT apparatus for scanning X-ray generating positions along a circumference of an examinee, comprising:

a ring-shaped vacuum tube;
a fixed cathode mounted in said vacuum tube and having a first thermion emitting surface;
a ring-shaped fixed anode mounted in said vacuum tube;
a ring-shaped rotatable cathode having a first thermion receiving surface opposed to said first thermion emitting surface, and a thermion emitting portion opposed to said fixed anode, said thermion emitting portion including a filament electrified in a non-contact state, said first thermion emitting surface and said thermion receiving surface forming part of a thermion supply passage for supplying thermions to said thermion emitting portion, and forming part of a circuit for applying a high voltage between said rotatable cathode and said fixed anode;
magnetic suspending means for suspending said ring-shaped rotatable cathode to a non-contact state, and
magnetic drive means for rotating said ring-shaped rotatable cathode.

3 more elements

Dependencies are inferred from the claim text.