Method for determining final projection matrices

• US 7,912,271 B2
• Filed: 09/20/2007
• Issued: 03/22/2011
• Est. Priority Date: 09/21/2006
• Status: Active Grant

• Current Assignee: Siemens Healthcare GMBH (Siemens AG)
• Original Assignee: Siemens AG
• Inventors: Hornegger, Joachim, Hoppe, Stefan, Lauritsch, Günter
• Primary Examiner(s): Tucker; Wesley
• Assistant Examiner(s): Bitar; Nancy
• Application Number:
  US11/903,164
• Publication Number:
  US 20080080758A1
• Time in Patent Office: 1,279 Days
• Field of Search: 382/128, 382/130, 382/131, 382/132, 378/4, 378/210, 378/901, 378/205, 345/473, 345/646
• US Class Current: 382/132
• 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 6/583 using calibration phantoms
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

A computer receives a number of groups of projection images of a reference object already known to the computer. Each projection image was captured via a recording arrangement with corresponding positioning of the recording arrangement. The computer uses one projection image for the respective position of the recording arrangement to determine an interim projection matrix, which describes a mapping of the three-dimensional space to a projection image captured with the respective positioning of the recording arrangement. The interim projection matrices relate to coordinate systems that are specifically assigned to each group. The computer uses interim projection matrices of different groups determined for the same position of the recording arrangement to determine locations of the other coordinate systems related to one of the coordinate systems. The computer uses the interim projection matrices and locations of the other coordinate systems to define a final projection matrix, that relates to a uniform coordinate system, for every position of the recording arrangement.

Claims

1. A method for determining final projection matrices, comprising:

capturing a plurality of projection images via a recording arrangement with corresponding positioning of the recording arrangement;

receiving by a computer a plurality of groups of projection images of a reference object already known to the computer;

determining an interim projection matrix via one of the plurality of projection images for the respective position of the recording arrangement, where the interim projection matrix describes a mapping of the three-dimensional space to a projection image captured with respective positioning of the recording arrangement and being related to a coordinate system;

assigning a specific coordinate system to each groups of projection images;

determining locations of the other coordinate systems related to one of the coordinate systems by the computer using interim projection matrices of different groups determined for the same position of the recording arrangement; and

defining the final projection matrix by the computer using the interim projection matrices and the locations of other coordinate systems for each position of the recording arrangement, wherein the final projection matrices relate to a uniform coordinate system.

2. The method as claimed in claim 1, wherein the interim projection matrices and the final projection matrices are 3×

4 matrices, that define a projective mapping.

3. The method as claimed in claim 2, wherein the computer adopts the interim projection matrix for at least one position of the recording arrangement, for which it has determined an interim projection matrix related to the one coordinate system, as the final projection matrix and determines the final projection matrix for at least one position of the recording arrangement, for which it has determined an interim projection matrix related to another coordinate system, based on the respective interim projection matrix related to the other coordinate system and the location of the other coordinate system.

4. The method as claimed in claim 3, wherein the final projection matrices form a sequence having sub-segments, the final projection matrices of each sub-segment correspond to a locally contiguous segment of a scan path, along which the recording arrangement is displaced and the computer determines the final projection matrices based on the interim projection matrices of the same group within each sub-segment.

5. The method as claimed in claim 4, wherein the computer determines a homographic transformation matrix for every other coordinate system, by means of which the three-dimensional space of the respective other coordinate system is transformed to the one coordinate system and the computer uses the respective homographic transformation matrix to transform the interim projection matrices related to the respective other coordinate system to the one coordinate system.

6. The method as claimed in claim 5, wherein the computer determines the homographic transformation matrices by resolving linear equation systems.

7. The method as claimed in claim 6, wherein the computer carries out a singular value decomposition to resolve the linear equation systems.

8. A non-transitory computer readable medium storing a computer program for execution by a computer comprising:

receiving by the computer a plurality of groups of projection images of a reference object already known to the computer,

determining an interim projection matrix via one of a plurality of captured projection images for the respective position of the recording arrangement, where the interim projection matrix describes a mapping of the three-dimensional space to a projection image captured with respective positioning of the recording arrangement and being related to a coordinate system, wherein the captured projection images are captured via a recording arrangement;

assigning a specific coordinate system to each group of projection images;

determining locations of the other coordinate systems related to one of the coordinate systems by the computer using interim projection matrices of different groups determined for the same position of the recording arrangement; and

defining the final projection matrix by the computer using the interim projection matrices and the locations of other coordinate systems for each position of the recording arrangement, wherein the final projection matrices relate to a uniform coordinate system.

9. The non-transitory computer readable medium as claimed in claim 8, wherein the interim projection matrices and the final projection matrices are 3×

4 matrices, that define a projective mapping.

10. The non-transitory computer readable medium as claimed in claim 9, wherein the computer adopts the interim projection matrix for at least one position of the recording arrangement, for which it has determined an interim projection matrix related to the one coordinate system, as the final projection matrix and determines the final projection matrix for at least one position of the recording arrangement, for which it has determined an interim projection matrix related to another coordinate system, based on the respective interim projection matrix related to the other coordinate system and the location of the other coordinate system.

11. The non-transitory computer readable medium as claimed in claim 10, wherein the final projection matrices form a sequence having sub-segments, the final projection matrices of each sub-segment co/respond to a locally contiguous segment of a scan path, along which the recording arrangement is displaced and the computer determines the final projection matrices based on the interim projection matrices of the same group within each sub-segment.

12. The non-transitory computer readable medium as claimed in claim 11, wherein the computer determines a homographic transformation matrix for every other coordinate system, by means of which the three-dimensional space of the respective other coordinate system is transformed to the one coordinate system and the computer uses the respective homographic transformation matrix to transform the interim projection matrices related to the respective other coordinate system to the one coordinate system.

13. The non-transitory computer readable medium as claimed in claim 12, wherein the computer determines the homographic transformation matrices by resolving linear equation systems.

14. The non-transitory computer readable medium as claimed in claim 13, wherein the computer carries out a singular value decomposition to resolve the linear equation systems.

15. A computer, comprising:

a processor;

an input device;

and output device; and

a mass storage device having a stored program that;

receives a plurality of groups of projection images of a reference object already known to the computer;

determines an interim projection matrix via one of a plurality of captured projection images for the respective position of the recording arrangement, where the interim projection matrix describes a mapping of the three-dimensional space to a projection image captured with respective positioning of the recording arrangement and being related to a coordinate system, wherein the captured projection images are captured via a recording arrangement;

assigns a specific coordinate system to each group of projection images;

determines locations of the other coordinate systems related to one of the coordinate systems by the computer using interim projection matrices of different groups determined for the same position of the recording arrangement; and

defines the final projection matrix by the computer using the interim projection matrices and the locations of other coordinate systems for each position of the recording arrangement, wherein the final projection matrices relate to a uniform coordinate system.

16. The computer as claimed in claim 15, wherein the interim projection matrices and the final projection matrices are 3×

4 matrices, that define a projective mapping.

17. The computer as claimed in claim 16, wherein the computer adopts the interim projection matrix for at least one position of the recording arrangement, for which it has determined an interim projection matrix related to the one coordinate system, as the final projection matrix and determines the final projection matrix for at least one position of the recording arrangement, for which it has determined an interim projection matrix related to another coordinate system, based on the respective interim projection matrix related to the other coordinate system and the location of the other coordinate system.

18. The computer as claimed in claim 17, wherein the final projection matrices form a sequence having sub-segments, the final projection matrices of each sub-segment correspond to a locally contiguous segment of a scan path, along which the recording arrangement is displaced and the computer determines the final projection matrices based on the interim projection matrices of the same group within each sub-segment.

19. The computer as claimed in claim 18, wherein the computer determines a homographic transformation matrix for every other coordinate system, by means of which the three-dimensional space of the respective other coordinate system is transformed to the one coordinate system and the computer uses the respective homographic transformation matrix to transform the interim projection matrices related to the respective other coordinate system to the one coordinate system.

20. The computer as claimed in claim 19, wherein the computer determines the homographic transformation matrices by resolving linear equation systems.