X-ray CT apparatus

• US 6,580,777 B1
• Filed: 07/05/2001
• Issued: 06/17/2003
• Est. Priority Date: 01/05/1999
• Status: Expired due to Fees

• Current Assignee: Hitachi Medical Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi Medical Corporation (Hitachi, Ltd.)
• Inventors: Ueki, Hironori, Okajima, Kenichi
• Primary Examiner(s): Dunn, Drew A.
• Assistant Examiner(s): Kiknadze, Irakli
• Application Number:
  US09/869,851
• Time in Patent Office: 712 Days
• Field of Search: 378/15, 378/17, 378/4, 378/8, 378/196
• US Class Current: 378/17
• CPC Class Codes: A61B 6/027 characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4291 the detector being combined with a grid or grating
• CPC Class Codes: A61B 6/4447 Tiltable gantries

Abstract

An x-ray CT apparatus of the invention includes: a scanner (4) having an x-ray source (1) for generating radial x-rays emitted to an object (8) and a detector (3) provided to face the x-ray source and acquiring a projection of the object; a rotation controler (102) for rotating the scanner around the object; a gantry-tilt angle controler (104) for changing a tilt angle formed between a surface of rotation of the scanner and a body axis of the object; processing unit (106) for generating a CT image of the object from the projections acquired from a plurality of directions while rotating the scanner and changing the tilt angle; and display unit (107) for displaying a three-dimensional CT image of high picture quality.

Claims

1. An x-ray CT apparatus comprising:

a scanner on which a scanning system is mounted, the scanning system having an x-ray source for generating radial x-rays to be irradiated to an object and image acquiring means provided so as to face said x-ray source and acquiring projection images of said object;

rotating means for rotating said scanner around said object;

tilting means for changing a tilt angle formed between a surface of rotation of said scanner and a body axis of said object;

means for generating a CT image of said object from said projections images acquired from a plurality of directions while simultaneously rotating said scanner and changing said tilt angle; and

display means for displaying said CT image;

wherein said tilting means synchronizes a period of rotation of (360°

×

N) (where, N denotes a natural number) of said scanner by said rotating means with a period from a start until an end of the change of said tilt angle by said tilting means.

2. An x-ray CT apparatus comprising:

a scanner on which a scanning system is mounted, the scanning system having an x-ray source for generating radial x-rays to be irradiated to an object and image acquiring means provided so as to face said x-ray source and acquiring projection images of said object;

rotating means for rotating said scanner around said object;

tilting means for changing a tilt angle formed between a surface of rotation of said scanner and a body axis of said object;

means for generating a CT image of said object from said projections images acquired from a plurality of directions while simultaneously rotating said scanner and changing said tilt angle; and

display means for displaying said CT image;

wherein said tilting means synchronizes the period of rotation of (360°

×

I+α

) (where, I denotes a natural number and α

denotes an arbitrary angle in a range of 0°

<

α

<

360°

) of said scanner by said rotating means with a period from a start until an end of the change of said tilt angle by said tilting means.

3. An x-ray CT imaging method comprising:

a step of rotating a scanner on which a scanning system is mounted around an object, the scanning system having an x-ray source for generating radial x-rays to be irradiated to said object and image acquiring means provided so as to face said x-ray source and acquiring projection images of said object;

a tilting step of tilting a surface of rotation of said scanner to change a tilt angle formed between the surface of rotation of said scanner and a body axis of said object;

an image acquiring step of acquiring projection images of said object by using the x-rays transmitted through said object;

an image reproducing step of generating a CT image of said object from said projection images acquired from a plurality of directions while simultaneously rotating said scanner and changing said tilt angle; and

a display step of displaying said CT image of said object,

wherein a period of rotation of (360°

×

I+α

) (where, I denotes a natural number and α

denotes an arbitrary angle in a range of 0°

≦

α

<

360°

) of said scanner and a period from a start until an end of the change of said tilt angle are synchronized with each other.

4. The x-ray CT imaging method according to claim 3, further comprising a stopping step of temporarily stopping the change in said tilt angle during said rotating step.

5. The x-ray CT imaging method according to claim 3, wherein, in said tilting step, said tilt angle is changed so that an upper part of a gantry housing said scanner is moved away from a head of said object.

6. An x-ray CT apparatus comprising:

an x-ray source for generating x-rays to be irradiated to an object;

an x-ray detector for detecting x-rays transmitted through said object;

a scanner for scanning said object with the x-rays irradiated to said object, said scanner supporting said x-ray source and said x-ray detector so as to face each other and being provided with a rotating mechanism for rotating said x-ray source and said x-ray detector around said object;

a tilting mechanism for changing a tilt angle formed between the surface of rotation of said scanner and a body axis of said object, in a predetermined tilt angle range;

a bed for supporting said object in a position between said x-ray source and said x-ray detector;

control means for controlling the generation of the x-rays by said x-ray source, the detection of the transmitted x-rays by said x-ray detector, the rotation angle by said rotating mechanism and the tilt angle by said tilting mechanism so as to simultaneously carry out the rotation operation of said scanner and the tilting operation of changing the tilt angle by said tilting mechanism; and

image reconstruction means for reconstructing a 3D CT image of said object by using the detection signal of the transmitted x-rays by said x-ray detector;

wherein said tilting mechanism holds a constant change amount of said tilt angle with respect to a unit rotation amount of said scanner; and

wherein said tilting mechanism synchronizes a period of rotation of (360°

×

N) (where, N denotes a natural number) of said scanner by said rotating mechanism with a period from a start until an end of the change of said tilt angle by said tilting mechanism.

7. The x-ray CT apparatus according to claim 6, wherein said predetermined tilt angle range is set within a range from −

20°

to +20°

.

8. An x-ray CT apparatus comprising:

an x-ray source for generating x-rays to be irradiated to an object;

an x-ray detector for detecting x-rays transmitted through said object;

a scanner for scanning said object with the x-rays irradiated to said object, said scanner supporting said x-ray source and said x-ray detector so as to face each other and being provided with a rotating mechanism for rotating said x-ray source and said x-ray detector around said object;

a tilting mechanism for changing a tilt angle formed between the surface of rotation of said scanner and a body axis of said object, in a predetermined tilt angle range;

a bed for supporting said object in a position between said x-ray source and said x-ray detector;

control means for controlling the generation of the x-rays by said x-ray source, the detection of the transmitted x-rays by said x-ray detector, the rotation angle by said rotating mechanism and the tilt angle by said tilting mechanism so as to simultaneously carry out the rotation operation of said scanner and the tilting operation of changing the tilt angle by said tilting mechanism; and

image reconstruction means for reconstructing a 3D CT image of said object by using the detection signal of the transmitted x-rays by said x-ray detector;

wherein said tilting mechanism holds a constant change amount of said tilt angle with respect to a unit rotation amount of said scanner; and

wherein said tilting mechanism synchronizes a period of rotation of (360°

×

I+α

) (where, I denotes a natural number and a denotes an arbitrary angle in a range of 0°

<

α

<

360°

) of said scanner by said rotating mechanism with a period from a start until an end of the change of said tilt angle by said tilting mechanism.

9. An x-ray CT apparatus comprising:

a scanner on which a scanning system is mounted, the scanning system having an x-ray source for emitting radial x-rays to be irradiated to an object and image acquiring means provided so as to face said x-ray source and acquiring projection images of said object by using the x-rays transmitted through said object;

rotating means for rotating said scanner around said object;

tilting means for changing a tilt angle formed between a surface of rotation of said scanner and a body axis of said object;

means for controlling operations of said rotating means and said tilting means so that the rotating of said scanner and the changing of said tilt angle are simultaneously carried out; and

means for generating a CT image of said object from said projection images acquired from a plurality of directions while simultaneously rotating said scanner and changing said tilt angle; and

display means for displaying said CT image;

wherein said tilting means holds a constant change amount of said tilt angle with respect to a unit rotation amount of said scanner; and

wherein said tilting means synchronizes a period of the rotation of (360°

×

N) (where, N denotes a natural number) of said scanner by said rotating means with a period from a start until an end of the change of said tilt angle by said tilting means.

10. An x-ray CT apparatus comprising:

a scanner on which a scanning system is mounted, the scanning system having an x-ray source for emitting radial x-rays to be irradiated to an object and image acquiring means provided so as to face said x-ray source and acquiring projection images of said object by using the x-rays transmitted through said object;

rotating means for rotating said scanner around said object;

tilting means for changing a tilt angle formed between a surface of rotation of said scanner and a body axis of said object;

means for controlling operations of said rotating means and said tilting means so that the rotating of said scanner and the changing of said tilt angle are simultaneously carried out; and

means for generating a CT image of said object from said projection images acquired from a plurality of directions while simultaneously rotating said scanner and changing said tilt angle; and

display means for displaying said CT image;

wherein said tilting means holds a constant change amount of said tilt angle with respect to a unit rotation amount of said scanner; and

wherein said tilting means synchronizes a period of the rotation of (360°

×

I+α

) (where, I denotes a natural number and a denotes an arbitrary angle in a range of 0°

<

α

<

360°

) of said scanner by said rotating means with a period from a start until an end of the change of said tilt angle by said tilting means.

11. An x-ray CT imaging method comprising the steps of:

rotating a scanner on which a scanning system is mounted around an object, the scanning system having an x-ray source for generating radial x-rays to be irradiated onto said object and image acquiring means provided so as to face said x-ray source and acquiring projection images of said object, and tilting the surface of the rotation of said scanner to change the tilt angle formed between the surface of the rotation of said scanner and a body axis of said object, wherein the rotation of said scanner and the changing of the tilt angle are simultaneously carried out;

acquiring projection images from a plurality of directions of said object by using the x-rays transmitted through said object; and

,

reproducing a CT image of said object from said projection images while simultaneously rotating said scanner and changing said tilt angle; and

displaying said CT image of said object;

wherein the period of the rotation of (360°

×

I+α

) (where, I denotes a natural number and α

denotes an arbitrary angle in a range of 0°

<

α

<

360°

) of said scanner and a period from a start until an end of the change of said tilt angle are synchronized.