Filter arrangement for ct system having a plurality of x-ray sources

Patent metadata

Field	Value
Publication number	US-2016296183-A1
Application number	US-201615077939-A
Country	US
Kind code	A1
Filing date	Mar 23, 2016
Priority date	Apr 9, 2015
Publication date	Oct 13, 2016
Grant date	—

Abstract

A filter arrangement is described. The filter arrangement includes an inner filter region, covering a cross-sectional area of a fan beam of a first X-ray source, and an outer filter region covering, together with the inner filter region, a larger cross-sectional area of a larger fan beam of a second X-ray source. The inner filter region has a first spectral filter function. The outer filter region is divided into a first subregion having a second spectral filter function and a second subregion having a third different spectral filter function. A computed tomography system is described. A method for producing a filter arrangement for a spectral filtering of X-ray radiation of a CT system having a first X-ray source and a second X-ray source is also presented. A method for reconstructing image data on the basis of projection measurement data is also described.

First claim

What is claimed is:

1 . A filter arrangement for a spectral filtering of X-ray radiation of a CT system including a first and a second X-ray source, comprising:
an inner filter region, to cover an inner partial cross-sectional area of a fan beam of the second X-ray source with a second, relatively larger fan-beam arc, the inner partial cross-sectional area being chosen in accordance with first, relatively smaller fan-beam arc of a fan beam of the first X-ray source, the inner filter region including a first spectral filter function; and an outer filter region to, together with the inner filter region, cover a cross-sectional area of the fan beam of the second X-ray source, which is relatively larger in relation to the partial cross-sectional area, the outer filter region being divided into two subregions in a direction of the system axis of the CT system, the first subregion including a second spectral filter function and the second subregion including a third spectral filter function, different from the second filter function.

2 . The filter arrangement of claim 1 , wherein the filter arrangement is designed as a prefilter arrangement.

3 . The filter arrangement of claim 1 , wherein the inner filter region includes a first filter material to cover an entire width of a detector of the CT systems in a direction of the system axis.

4 . The filter arrangement of claim 3 , wherein the first filter material comprises tin.

5 . The filter arrangement of claim 3 , wherein the outer filter region includes a second filter material and a third filter material, different from the second filter material.

6 . The filter arrangement of claim 5 , wherein at least one of:
the second filter material comprises tin, and the third filter material comprises gold.

7 . The filter arrangement of claim 1 , wherein at least one of
the first subregion and the second subregion of the outer filter region include differing thicknesses or differing densities, and the first subregion and the second subregion of the outer filter region each occupy half of the outer filter region.

8 . The filter arrangement of claim 1 , wherein the first subregion and the second subregion of the outer filter region meet in a center of the outer filter region when viewed in a direction of the system axis.

9 . A computed tomography system, comprising:
a first X-ray source with a first X-ray energy level, to emit a first fan beam with a first fan-beam arc; a second X-ray source with a second X-ray energy level, to emit a second fan beam with a second fan-beam arc, the second fan-beam arc being relatively larger than the first fan-beam arc; a first X-ray detector, to detect the first fan beam emitted by the first X-ray source; a second X-ray detector, to detect the second fan beam emitted by the second X-ray source; and the filter arrangement of claim 1 .

10 . The computed tomography system of claim 9 , wherein the first X-ray detector includes a relatively smaller extent in the fan-beam direction than the second X-ray detector.

11 . The computed tomography system of claim 9 , wherein the computed tomography system is set up to perform an image capture operation using a pitch of a spiral scan of less than 0.75.

12 . The computed tomography system of claim 10 , wherein the computed tomography system is set up to perform an image capture operation using a pitch of a spiral scan of less than 0.75.

13 . A method for producing a filter arrangement for a spectral filtering of X-ray radiation of a CT system including a first X-ray source and a second X-ray source, comprising:
forming an inner filter region, covering an inner partial cross-sectional area of a fan beam of the second X-ray source with a second, relatively larger fan-beam arc, wherein the partial cross-sectional area is chosen in accordance with a first, relatively smaller fan-beam arc of a fan beam of the first X-ray source, and includes a first spectral filter function; forming an outer filter region to, together with the inner filter region, cover a cross-sectional area of the fan beam of the second X-ray source which is relatively larger in relation to the partial cross-sectional area; dividing the outer filter region into two subregions in a direction of the system axis through design of the first subregion with a second spectral filter function and design of the second subregion with a third spectral filter function, different from the second spectral filter function.

14 . A method for reconstructing image data on the basis of projection measurement data which has been acquired via a computed tomography system including a first X-ray source and a second X-ray source, a first X-ray detector to detect a first fan beam emitted by the first X-ray source and a second X-ray detector to detect a second fan beam emitted by the second X-ray source, and a filter arrangement, the method comprising:
separating the projection measurement data from outer detector regions of the second detector depending on whether the projection measurement data is assigned to a first subregion of an outer filter region of the filter arrangement or whether the projection measurement data is assigned to a second subregion of the outer filter region of the filter arrangement; assigning the separated projection measurement data of the first subregion of the outer filter region of the filter arrangement to the projection measurement data of the second X-ray detector such that a first projection data set is formed on the basis of acquired X-ray radiation having a first X-ray spectrum; assigning the separated projection measurement data of the second subregion of the outer filter region of the filter arrangement to the projection measurement data of the first X-ray detector such that a second projection data set is formed on the basis of acquired X-ray radiation having a second X-ray spectrum; and separating reconstruction of image data on the basis of the projection measurement data of the first projection data set and of the second projection data set.

15 . A non-transitory computer readable medium, loadable directly into a memory facility of a computed tomography system, comprising program sections to execute the method of claim 14 when executed in the memory facility.

16 . The filter arrangement of claim 1 , wherein the inner filter region is designed as a single piece.

17 . The filter arrangement of claim 2 , wherein the inner filter region is designed as a single piece.

18 . The filter arrangement of claim 2 , wherein the inner filter region includes a first filter material to cover an entire width of a detector of the CT systems in a direction of the system axis.

19 . The filter arrangement of claim 18 , wherein the first filter material comprises tin.

20 . The filter arrangement of claim 3 , wherein the first filter material and the second filter material are identical.

21 . The filter arrangement of claim 5 , wherein the first filter material and the second filter material are identical.

22 . The filter arrangement of claim 21 , wherein at least one of:
the second filter material comprises tin, and the third filter material comprises gold.

23 . A computed tomography system, comprising:
a first X-ray source with a first X-ray energy level, to emit a first fan beam with a first fan-beam arc; a second X-ray source with a second X-ray energy level, to emit a second fan beam with a second fan-beam arc, the second f

Assignees

• Siemens Ag

Inventors

• Flohr Thomas
• Schmidt Bernhard

Classifications

• A61B6/4014

  arranged in multiple source-detector units · CPC title

• A61B6/482

  involving multiple energy imaging · CPC title

• A61B6/4035 Primary

  the source being combined with a filter or grating · CPC title

• A61B6/5211

  involving processing of medical diagnostic data · CPC title

• A61B6/4078

  Fan-beams · CPC title