X-ray CT apparatus

• US 7,535,987 B2
• Filed: 06/29/2006
• Issued: 05/19/2009
• Est. Priority Date: 06/30/2005
• Status: Expired due to Fees

• Current Assignee: Toshiba Medical Systems Corporation (Canon Inc.), Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Toshiba Medical Systems Corporation (Canon Inc.), Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Matsuda, Keiji
• Primary Examiner(s): Kao; Chih-Cheng G
• Application Number:
  US11/427,633
• Publication Number:
  US 20070003005A1
• Time in Patent Office: 1,055 Days
• Field of Search: 378/4, 378/9, 378/15, 378/901, 378/159, 378/7, 378/16
• US Class Current: 378/7
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 2223/612 biological material
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• CPC Class Codes: H05G 1/70 Circuit arrangements for X-ray tubes with more than one anode; Circuit arrangements for apparatus comprising more than one X ray tube or more than one cathode H05G1/58 takes precedence

Abstract

An X-ray CT apparatus includes a plurality of X-ray tubes, a plurality of X-ray detectors corresponding to the plurality of X-ray tubes, respectively, a support mechanism which supports the X-ray tubes and the X-ray detectors to allow the X-ray tubes and the X-ray detectors to rotate about a single rotation axis, a reconstruction unit which reconstructs image data on the basis of outputs from the X-ray detectors, and a plurality of filters which are respectively provided for the plurality of X-ray tubes and each have a characteristic in which an X-ray path length changes along a curve approximate to an inverted Gaussian curve from the rotation center to the two ends of an X-ray beam.

Claims

1. An X-ray CT apparatus, comprising:

a plurality of X-ray tubes;

a plurality of X-ray detectors corresponding to said plurality of X-ray tubes, respectively, each X-ray tube and corresponding X-ray detector forming a pair;

a support mechanism which supports the X-ray tubes and the X-ray detectors to allow the X-ray tubes and the X-ray detectors to rotate about a single rotation axis;

a reconstruction unit which reconstructs image data on the basis of outputs from the X-ray detectors; and

a plurality of filters corresponding to said plurality of X-ray tubes, each filter having a characteristic in which an X-ray path length changes as a function substantially equal to an inverted Gaussian curve from the rotation center to two ends of an X-ray beam so as to reduce scattering radiation originating from X-rays generated by an X-ray tube of a first pair, but detected by an X-ray detector of a second, different pair;

wherein said each filter has a characteristic in which an intensity of X-rays transmitted through the filter exceeds 90% of a maximum intensity at the rotation center at a middle portion less than 10 cm away from the rotation center, and an intensity at a peripheral portion more than 20 cm away from the rotation center is less than 50% of the maximum intensity at the rotation center.

2. An apparatus according to claim 1, further comprising a mechanism which attaches/detaches the filters.

3. An apparatus according to claim 1, which further comprises a plurality of slits which are respectively provided for said plurality of X-ray tubes and limit X-ray thicknesses, and in which

the filter is placed between the X-ray tube and the slit.

4. An apparatus according to claim 1, wherein said each filter further has a characteristic in which an intensity of X-rays transmitted through said each filter changes as a function substantially equal to a Gaussian curve from the rotation center to two ends of an X-ray beam.

5. An apparatus according to claim 1, wherein said each filter further has a characteristic in which an intensity of X-rays transmitted through said each filter and a cylindrical homogeneous phantom changes curvilinearly from the rotation center to two ends of an X-ray beam.

6. An apparatus according to claim 1, wherein said each filter has a curved surface shape with a thickness of a central portion being small, and a thickness gradually increasing toward peripheral portions.

7. An X-ray CT apparatus, comprising:

a plurality of X-ray tubes;

a plurality of X-ray detectors corresponding to said plurality of X-ray tubes, respectively, each X-ray tube and corresponding X-ray detector forming a pair;

a support mechanism which supports the X-ray tubes and the X-ray detectors to allow the X-ray tubes and the X-ray detectors to rotate about a single rotation axis;

a reconstruction unit which reconstructs image data on the basis of outputs from the X-ray detectors; and

a plurality of filters corresponding to said plurality of X-ray tubes and each have a characteristic in which an intensity of X-rays transmitted through the filter exceeds 90% of a maximum intensity at the rotation center at a middle portion less than 10 cm away from the rotation center, and an intensity at a peripheral portion more than 20 cm away from the rotation center is less than 50% of the maximum intensity at the rotation center so as to reduce scattering radiation originating from X-rays generated by an X-ray tube of a first pair, but detected by an X-ray detector of a second, different pair.

8. A filter provided for an X-ray tube of an X-ray CT apparatus, which has a characteristic in which an X-ray path length changes as a function equal to an inverted Gaussian curve from a center to two ends.

9. The filter of claim 8, wherein the filter has a characteristic in which an intensity of X-rays transmitted through the filter and a cylindrical homogenous phantom gradually change such that the intensity at the ends of the X-ray beam is 20%-80% of the intensity at a rotation center.

10. A filter provided for an X-ray tube of an X-ray CT apparatus, which has a characteristic in which an intensity of X-rays transmitted through the filter exceeds 90% of a maximum intensity at a center throughout a middle portion less than 10 cm away from the center, and an intensity throughout a peripheral portion more than 20 cm away from the center is less than 50% of the maximum intensity at the center.