X-ray computer tomography apparatus

• US 20060008048A1
• Filed: 09/16/2004
• Published: 01/12/2006
• Est. Priority Date: 07/06/2004
• Status: Active Grant

• Current Assignee: Toshiba Medical Systems Corporation (Canon Inc.)
• Original Assignee: Toshiba Medical Systems Corporation (Canon Inc.)
• Inventors: Rifu, Toshihiro, Katada, Kazuhiro
• Granted Patent: US 7,123,680 B2
• Time in Patent Office: Days
• US Class Current: 378/16
• 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 6/06 Diaphragms
• CPC Class Codes: G21K 1/04 using variable diaphragms, shutters, choppers
• CPC Class Codes: G21K 1/043 changing time structure of beams by mechanical means, e.g. choppers, spinning filter wheels

Abstract

An X-ray computer tomography apparatus includes an X-ray tube, an X-ray detector, a data collection apparatus that collects X-ray signals from the X-ray detector repeatedly, a shutter mechanism that is arranged between the X-ray tube and a subject in order to convert an X-ray into a pulse-like X-ray and is constituted such that a ratio of a shutter open period and a shutter close period is variable, a restructuring unit that restructures image data on the basis of the collected X-ray signals, and a control unit that controls the shutter mechanism in order to change the ratio of a shutter open period and a shutter close period during a helical scan.

Claims

1. An X-ray computer tomography apparatus comprising:

an X-ray tube that generates an X-ray;

an X-ray detector for detecting an X-ray transmitted through a subject;

a collection unit that collects X-ray signals from the X-ray detector repeatedly;

a shutter mechanism unit that is arranged between the X-ray tube and the subject in order to convert the generated X-ray into a pulse X-ray and is constituted such that a ratio of a shutter open period and a shutter close period is variable;

a restructuring unit that restructures image data on the basis of the collected X-ray signals; and

a control unit that controls the shutter mechanism unit in order to change the ratio of a shutter open period and a shutter close period.

2. An X-ray computer tomography apparatus according to claim 1, wherein the control unit changes the ratio of a shutter open period and a shutter close period dynamically during a helical scan.

3. An X-ray computer tomography apparatus according to claim 2, wherein the control unit calculates the ratio of a shutter open period and a shutter close period individually with respect to plural slice positions on the basis of scanogram data of the subject.

4. An X-ray computer tomography apparatus according to claim 3, wherein the control unit controls the shutter mechanism unit in accordance with the calculated ratio.

5. An X-ray computer tomography apparatus according to claim 1, wherein the shutter mechanism has a disc-like X-ray shielding plate having at least one aperture that is arranged substantially perpendicular to a center axis of the X-ray and is formed such that an aperture ratio in a circumferential direction thereof changes with respect to a radial direction thereof.

6. An X-ray computer tomography apparatus according to claim 5, wherein the aperture unit is formed such that the aperture ratio changes stepwise with respect to the radial direction.

7. An X-ray computer tomography apparatus according to claim 5, wherein the aperture is formed such that the aperture ratio changes continuously with respect to the radial direction.

8. An X-ray computer tomography apparatus according to claim 5, wherein the shutter mechanism includes:

a rotation mechanism that axially rotates the X-ray shielding plate; and

a movement mechanism that moves the X-ray shielding plate in the radial direction of the X-ray shielding plate together with the rotating mechanism.

9. An X-ray computer tomography apparatus according to claim 8, wherein the control unit control the movement mechanism in order to move the X-ray shielding plate in the radial direction to change the ratio.

10. An X-ray computer tomography apparatus according to claim 8, further comprising an input unit that inputs a physical constitution of the subject, wherein the control unit moves the X-ray shielding plate on the basis of the inputted physical constitution of the subject.

11. An X-ray computer tomography apparatus according to claim 8, wherein the control unit controls the movement mechanism on the basis of scanogram data of the subject.

12. An X-ray computer tomography apparatus according to claim 8, wherein the control unit moves the X-ray shielding plate on the basis of an X-ray signal at a point a half rotation earlier or an angle rotation integer times the half rotation earlier.

13. An X-ray computer tomography apparatus according to claim 8, further comprising:

a detection unit for detecting rotation of the X-ray shielding plate; and

a trigger generation unit that generates a trigger for promoting the collection of the X-ray signals on the basis of an output of the detection unit.

14. An X-ray computer tomography apparatus according to claim 13, wherein the trigger generation unit generates a trigger such that a pulse width of the X-ray is at least within the cycle.

15. An X-ray computer tomography apparatus according to claim 1, wherein the shutter mechanism includes:

plural disc-like X-ray shielding plates with a variable angle difference that are stacked and have at least one aperture; and

a rotation mechanism that rotates the plural X-ray shielding plates.

16. An X-ray computer tomography apparatus comprising:

an X-ray tube that generates an X-ray;

an X-ray detector for detecting an X-ray transmitted through a subject;

a collection unit that collects X-ray signals from the X-ray detector repeatedly;

a shutter mechanism unit that is arranged between the X-ray tube and the subject in order to change a ratio of a shutter open period and a shutter close period dynamically during a helical scan; and

a restructuring unit that restructures image data on the basis of the collected X-ray signals.