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1. (WO2019048502) DYNAMIC BOWTIE FILTER AND METHODS OF USING THE SAME
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CLAIMS

What is claimed is:

1. An imaging system (700), comprising:

a radiation source (708) configured to emit radiation that traverses an examination region

(706);

a radiation detector array (716) having a plurality of detectors (1104N) configured to detect the radiation traversing the examination region;

a dynamic bowtie filter (718), disposed between the radiation source and the examination region, wherein the dynamic bowtie filter comprises a first half wedge (718i) and a separate and distinct second half wedge (7182) with a material free space there between;

a first motor (722i) in mechanical communication with the first half wedge, wherein the first motor is configured to move the first half wedge;

a second motor (7222) in mechanical communication with the second half wedge, wherein the second motor is configured to move the second half wedge; and

a controller (724) configured to independently control the first and second motors to move the first and second half wedges to increase or decrease a distance there between during an acquisition interval.

2. The system of claim 1, wherein the first half wedge and the second half wedge are a same size, shape, and density.

3. The system of any of claims 1 to 2, wherein the controller moves both the first half wedge and second half wedge in a same direction at a point in time.

4. The system of any of claims 1 to 2, wherein the controller moves both the first half wedge and second half wedge in opposite directions at a point in time.

5. The system of claim 1, wherein the first and second motors are linear motors.

6. The system of claim 5, further comprising:

a console (730) configured to determine a geometric center of an object or subject by creating a mathematical body (1200) from a survey scan of the object or subject.

7. The system of any of claims 1 to 5, wherein the controller moves at least one of the first half wedge and the second half wedge from a first location to a different location, which reduces an x-ray fluence at the radiation detector array.

8. The system of any of claims 1 to 7, further comprising:

a first mover 7201 and a second mover 7202, wherein the first mover is coupled to a first half wedge holder 902i and the first motor and the second mover is coupled to the second half wedge holder 9022 and the second motor, and the first half wedge holder is coupled to the first half wedge and the second half wedge holder is coupled to the second half wedge.

9. A computer readable storage medium encoded with computer executable instructions which when executed by a processor causes the processor to :

obtain a projection image of a subject or object generated with a survey scan of the subject or object;

create a mathematical ellipse for the subject or object from the projection image;

estimate, for an acquisition angle, a first fluence at a detector of a detector array with the mathematical ellipse with a first half wedge or a second half wedge of a bowtie filter at a first position;

compare the first estimated fluence with a predetermined fluence acceptance criterion; and

add the first position to a position profile only in response to the first estimated fluence satisfying the predetermined fluence acceptance criterion.

10. The computer readable storage medium of claim 9, wherein the instructions further cause the processor to:

in response to the first estimated fluence not satisfying the predetermined fluence acceptance criterion,

estimate a second fluence at the detector with the mathematical ellipse with the first half wedge or the second half wedge at a second position;

compare the second estimated fluence with the predetermined fluence acceptance criterion; and

add the second position to the position profile only in response to the second estimated fluence satisfying the predetermined fluence acceptance criterion.

1 1. The computer readable storage medium of any of claims 9 to 10, wherein the instructions further cause the processor to:

repeat the acts of estimate and compare for different positions until a current fluence estimate for a current position satisfies the predetermined fluence acceptance criterion; and

add the current position to the position profile when the second estimated fluence satisfies the predetermined fluence acceptance criterion.

12. The computer readable storage medium of any of claims 9 to 11, wherein the instructions further cause the processor to:

repeat the acts of estimate, compare, and add for one or more other detectors of the detector array for the acquisition angle.

13. The computer readable storage medium of claim 12, wherein the instructions further cause the processor to :

repeat the acts of estimate, compare, and add for other acquisition angles of an axial image.

14. The computer readable storage medium of any of claims 9 to 13, wherein the instructions further cause the processor to:

move the first wedge or the second half wedge during a scan of the subject or object based on the positions in the position profile.

15. The computer readable storage medium of claim 14, wherein the first wedge and the second half wedge independently move during the scan.

16. The computer readable storage medium of any of claims 9 to 15, wherein a fluence at the detector is computed as a product of an x-ray fluence of an x-ray beam leaving a radiation source, an estimated attenuation by a portion of the half wedge through which the beam traverses, and an estimated attenuation by a portion of the ellipse through which the beam traverses.

17. A method comprising

attenuating rays of an emitted radiation beam during a scan of a subject or object with a dynamic bowtie filter, wherein the dynamic bowtie filter comprises a first half wedge and a second half wedge; and

independently moving, with a controller, the first half wedge and the second half wedge to increase or decrease a distance between the first and second half wedges during a scan based on a predetermined wedge position profile.

18. The method of claim 17 further comprising

performing a survey scan of the subject or object, producing a projection image of the subject or object;

identifying a contour and a center point of the subject or object from the projection image;

creating a water-equivalent homogeneous ellipse for the subject or object using the center point; and

determining the predetermined wedge position profile based on the water-equivalent homogeneous ellipse.

19. The method of claim 18 further comprising:

mathematically determining a position of the first half wedge or the second half wedge at which a fluence at a detector satisfies a predetermined fluence acceptance criterion.

20. The method of claim 19 further comprising:

creating the predetermined wedge position profile with positions of the first half wedge and the second half wedge at which fluences at the detectors satisfy the predetermined fluence acceptance criterion.