Tomographic imaging with asymmetric detection

Patent metadata

Field	Value
Publication number	US-9439617-B2
Application number	US-201314029941-A
Country	US
Kind code	B2
Filing date	Sep 18, 2013
Priority date	Oct 1, 2012
Publication date	Sep 13, 2016
Grant date	Sep 13, 2016

Abstract

A recording unit is rotatable about an axis of rotation, and includes an X-ray emitter and detector to detect X-rays from a fan-shaped region. The fan-shaped region is asymmetrical in relation to a vertical to the axis of rotation, running through the X-ray detector wherein the two edges of the fan-shaped region, on rotation, in each case tangentially delimit a first projection region and a second projection region. The second projection region abuts the first projection region. A method includes recording projections of the two projection regions during a full rotation of the recording unit for the reconstruction of a first image of the first projection region in such a way that the projection angle intervals in each case exhibit the same start angle. It further includes reconstructing a second image of the second projection region to merge the two reconstructed projection regions to form one unitary image.

First claim

What is claimed is:

1. A method for tomographic imaging via a recording unit, rotatable about an axis of rotation, including an X-ray emitter and an X-ray detector arranged to detect X-rays from a fan-shaped region, wherein the fan-shaped region is asymmetrical in relation to a line orthogonal to the axis of rotation, the line running through the X-ray detector, wherein each of two edges of the fan-shaped region, on rotation, respectively delimit a first projection region and a second projection region tangentially, and wherein the second projection region abuts the first projection region, the method comprising:
recording projections of the two projection regions, wherein the recording unit carries out at least one full rotation;
reconstructing a first image of the first projection region such that the projection angle interval for each of the reconstruction of points in the first image, respectively exhibits a same start angle, the projection angle interval associated with respective ones of the points in the first image being an interval between two complementary projections of the respective ones of the points, the start angle for reconstruction of the first image being a first projection angle for the reconstruction of the points in the first image;
reconstructing a second image of the second projection region, wherein the start angle for the reconstruction of a point in the second image is selected based on a projection angle interval and a position of the respective point, the projection angle interval associated with respective ones of the points in the second image being an interval between two complementary projections of the respective ones of the points, the start angle for the reconstruction of the second image being a first projection angle for the reconstruction of points the second image such that each of the plurality of points within the second projection region has its own start angle associated therewith; and
merging the reconstructed first and second images to form one overall image of the first and second projection regions.

2. The method of claim 1 , wherein, for the reconstruction of a point in the second image, the projection angle interval is selected such that all the projections to which the respective point contributes are used for the reconstruction of the point.

3. The method of claim 1 , wherein, for the reconstruction of a point in the second image, the projection angle interval is delimited by two complementary projections of the respective point and is selected to be as small as possible.

4. The method of claim 2 , wherein, for the reconstruction of a point in the second image, a length of the projection angle interval lies between lengths of the projection intervals as claimed in claim 2 and a projection angle interval delimited by two complementary projections of the respective point and selected to be as small as possible.

5. The method of claim 1 , wherein the merging includes the first and second images being merged to form one overall image.

6. The method of claim 4 , further comprising:
reconstructing a third image of the first projection region, wherein, for the reconstruction of a point in the third image, the projection angle interval is selected in accordance with the projection angle interval as claimed in claim 4 .

7. The method of claim 6 , further comprising:
adding together the first and third images in accordance with a weighting function, wherein the merging includes the added together image and the second image to form one overall image.

8. The method of claim 7 , wherein the weighting function weights points from the third image more heavily as the distance interval from the axis of rotation increases.

9. The method of claim 6 , further comprising:
reconstructing several fourth images of the first projection region, wherein, for the reconstruction of different respective fourth images, different respective start angles are used.

10. The method of claim 1 , wherein the recording takes place in the form of a spiral scan with a pitch <0.5.

11. The method of claim 1 , wherein the recording is triggered by an EKG signal of a patient.

12. The method of claim 2 , further comprising:
reconstructing a third image of the first projection region, wherein, for the reconstruction of a point in the third image, the projection angle interval is selected in accordance with the projection angle interval as claimed in claim 2 .

13. The method of claim 12 , further comprising:
adding together the first and third images in accordance with a weighting function, wherein the merging includes the added together image and the second image to form one overall image.

14. The method of claim 13 , wherein the weighting function weights points from the third image more heavily as the distance interval from the axis of rotation increases.

15. A system for tomographic imaging, comprising:
a recording unit, rotatable about an axis of rotation, including an X-ray emitter and including an X-ray detector arranged to detect X-rays from a fan-shaped region, wherein the fan-shaped region is asymmetric in relation to a line orthogonal to the axis of rotation, the line running through the X-ray detector, wherein two edges of the fan-shaped region, on rotation, each delimit a respective one of a first projection region and a second projection region tangentially, wherein the second projection region abuts the first projection region, and wherein the recording unit is configured to record projections from the two projection regions during at least one full rotation;
a reconstruction unit, configured to,
reconstruct a first image of the first projection region in such a way that a respective projection angle interval for the reconstruction of each of a plurality of points in the first image each exhibit a same start angle, the projection angle interval associated with respective ones of the points in the first image being an interval between two complementary projections of the respective ones of the points, the start angle for reconstruction of the first image being a first projection angle for the reconstruction of the points in the first image, and
reconstruct a second image of the second projection region, wherein the start angle for the reconstruction of a respective point in the second image is selected based on a respective projection angle interval and a position of the respective point, the projection angle interval associated with respective ones of the points in the second image being an interval between two complementary projections of the respective ones of the points, the start angle for the reconstruction of the second image being a first projection angle for the reconstruction of points in the second image such that each of the plurality of points within the second projection region has its own start angle associated therewith; and

an image processing unit, configured to merge two reconstructed images to form one overall image of the first and second projection regions.

16. The system of claim 15 , wherein the X-ray detector is subdivided by the vertical into two at least one of differently shaped and different sized detector regions.

17. The system of claim 15 , wherein at least one detector region exhibits, on a relatively wide side, a side region which exhibits a relatively lesser expansion in the direction of the axis of rotation than the remaining relatively larger part of the detector region.

18. The system of claim 15 , arranged to carry out at least:
recording projections of the two projection regions, wherein

Assignees

• Siemens Ag

Inventors

• Flohr Thomas

Classifications

• A61B6/032

  Transmission computed tomography [CT] · CPC title

• A61B6/4233

  using matrix detectors · CPC title

• A61B6/5235 Primary

  combining images from the same or different ionising radiation imaging techniques, e.g. PET and CT · CPC title