# US 2014/0192950 A1 · Computed tomography system with dynamic bowtie filter

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- Number: US 2014/0192950 A1
- Document ID: US20140192950A1
- Status: Published application
- Kind: A1
- Application number: 14/125,926
- Filed: 2012-06-14
- Published: 2014-07-10
- Earliest claimed: 2011-06-17
- Assignees: The Board of Directors of the Leland Stanford Junior University
- Applicants: The Board of Directors of the Leland Stanford Junior University
- Inventors: Norbert J. Pelc; Scott Hsieh
- Web page: https://patentgrep.com/patent/US20140192950A1

## CPC

- A61B 6/4035: {the source being combined with a filter or grating}
- A61B 6/405: {Source units specially adapted to modify characteristics of the beam during the data acquisition process (A61B6/4021, A61B6/4035 take precedence)}
- G02B 5/201: {in the form of arrays}
- G21K 1/10: Scattering devices; Absorbing devices; Ionising radiation filters
- A61B 6/032: {Transmission computed tomography [CT]}
- A61B 6/06: Diaphragms
- A61B 6/4241: {using energy resolving detectors, e.g. photon counting}
- A61B 6/44: {Constructional features of apparatus for radiation diagnosis}
- A61B 6/547: {involving tracking of position of the device or parts of the device}
- A61B 6/583: {using calibration phantoms}
- G02B 5/22: Absorbing filters {(G02B5/201 - G02B5/208 take precedence)}
- G02B 26/02: for controlling the intensity of light {(G02B26/004 takes precedence)}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G21K: HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES

## Abstract

A CT apparatus for scanning an object is provided. An x-ray source is provided, wherein the x-ray source provides a collimated x-ray beam with a cross-section with a length and thickness. A plurality of wedges is provided between the source and object. An actuator is connected to the wedges for moving the wedges substantially perpendicular to the length of the cross-section of the collimated x-ray beam. An x-ray detector is located on an opposite side of the object from the x-ray source and is for detecting x-rays that pass through the object and the plurality of wedges. A gantry rotates the x-ray source, the plurality of wedges, and the x-ray detector around an axis of rotation.

## Claims

### Claim 1

A CT apparatus for scanning an object, comprising:
an x-ray source, wherein the x-ray source provides a collimated x-ray beam with a cross-section with a length and thickness;
a plurality of wedges between the source and object;
an actuator connected to a wedge of the plurality of wedges for moving the wedge substantially perpendicular to the length of the cross-section of the collimated x-ray beam;
an x-ray detector on an opposite side of the object from the x-ray source for detecting x-rays that pass through the object and the plurality of wedges; and
a gantry for rotating the x-ray source, the plurality of wedges, and the x-ray detector around an axis of rotation.

### Claim 2 (depends on 1)

The CT apparatus, as recited in claim 1, wherein wedges increase or decrease in thickness along direction of movement by the actuator.

### Claim 3 (depends on 2)

The CT apparatus, as recited in claim 2, wherein thicknesses of the wedges change in a direction along the length of the cross-section of the collimated x-ray beam.

### Claim 4 (depends on 3)

The CT apparatus, as recited in claim 3, wherein the thicknesses of the wedges alternately increase and decrease in a direction along the length of the cross-section of the collimated x-ray beam.

### Claim 5 (depends on 4)

The CT apparatus, as recited in claim 4, wherein a width of a cross-section of the wedges changes along a direction from the x-ray source to the object.

### Claim 6 (depends on 4)

The CT apparatus, as recited in claim 4, wherein the plurality of wedges comprises:
a first row of wedges; and
a second row of wedges, wherein the second row of wedges are placed to overlap with the first row of wedges in a direction from the x-ray source to the object.

### Claim 7 (depends on 6)

The CT apparatus, as recited in claim 6, wherein in the first row of wedges, each wedge of the first row of wedges has a thickness that increases in a first direction of movement by the actuators and in the second row of wedges, each wedge of the second row of wedges has a thickness that increases in the first direction.

### Claim 8 (depends on 7)

The CT apparatus, as recited in claim 7, wherein each wedge of the first row of wedges increases in width in a direction extending from the x-ray source to the object and wherein each wedge of the second row of wedges decrease in width in the direction extending from the x-ray source to the object.

### Claim 9 (depends on 1)

The CT apparatus, as recited in claim 1, wherein each wedge of the plurality of wedges comprises a smooth attenuation profile.

### Claim 10 (depends on 1)

The CT apparatus, as recited in claim 1, wherein at least one wedge of the plurality of wedges comprises at least one high-contrast marker.

### Claim 11 (depends on 1)

The CT apparatus, as recited in claim 1, further comprising a detection system for measuring the relative position of the plurality of wedges.

### Claim 12 (depends on 11)

The CT apparatus, as recited in claim 11, wherein the detection system for measuring the relative positions of the plurality of wedges comprises a thin detector between the object and the plurality of wedges.

### Claim 13 (depends on 11)

The CT apparatus, as recited in claim 11, wherein the detection system for measuring the relative position of the plurality of wedges comprises an optical tracking system.

### Claim 14 (depends on 1)

The CT apparatus, as recited in claim 1, wherein a width of the cross-section of the wedges changes along a direction from the x-ray source to the object.

### Claim 15 (depends on 1)

The CT apparatus, as recited in claim 1, wherein the plurality of wedges comprises:
a first row of wedges; and
a second row of wedges, wherein the second row of wedges are placed to overlap with the first row of wedges in a direction from the x-ray source to the object.

### Claim 16 (depends on 15)

The CT apparatus, as recited in claim 15, wherein in the first row of wedges, each wedge of the first row of wedges has a thickness that increases in a first direction of movement by the actuator and in the second row of wedges, each wedge of the second row of wedges has a thickness that increases in the first direction.

### Claim at position 17

17-29. (canceled)

### Claim 30

A method of providing dynamic bowtie filtering for scanning an object in a CT system, comprising:
analyzing a shape of the object;
moving at least one wedge to compensate for the shape of the body;
rotating the wedges, an x-ray source, and a detector around the object;
providing a collimated x-ray from the x-ray source with a cross-section with a length, wherein the moving the wedges moves the wedges perpendicular to the length of the cross-section;
passing the x-rays through the wedges and the object;
detecting the x-rays at the detector;
generating an image from the detected x-rays; and
displaying the image.

### Claim 31 (depends on 30)

The method, as recited in claim 30, wherein at least one of the wedges has at least one high-contrast marker, further comprising using locations of the at least one high-contrast marker to determine locations of the wedges.

### Claim 32 (depends on 31)

The method, as recited in claim 31, further comprising, measuring relative positions of the plurality of wedges.

### Claim 33 (depends on 32)

The method, as recited in claim 32, wherein wedges increase or decrease in thickness along direction of movement by the actuators.

### Claim at position 22

34-43. (canceled)