Method for determining density distributions and atomic number distributions during radiographic examination methods

• US 20040223585A1
• Filed: 03/03/2004
• Published: 11/11/2004
• Est. Priority Date: 09/03/2001
• Status: Active Grant

• Current Assignee: Siemens Healthcare GMBH (Siemens AG)
• Original Assignee: Siemens AG
• Inventors: Stierstorfer, Karl, Heismann, Bjorn
• Granted Patent: US 7,158,611 B2
• Time in Patent Office: Days
• US Class Current: 378/54
• CPC Class Codes: A61B 6/4035 the source being combined with a filter or grating
• CPC Class Codes: A61B 6/4241 using energy resolving detectors, e.g. photon counting
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 6/50 specially adapted for specific body parts; specially adapted for specific clinical applications
• CPC Class Codes: A61B 6/501 for diagnosis of the head, e.g. neuroimaging or craniography
• CPC Class Codes: A61B 6/502 for diagnosis of breast, i.e. mammography
• CPC Class Codes: A61B 6/505 for diagnosis of bone
• CPC Class Codes: A61B 6/508 for non-human patients
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: G01N 23/04 and forming images of the material

Abstract

The functional dependency of a first X-ray absorption value of density and atomic number is determined in the instance of a first X-ray spectrum, and at least the functional dependency of a second X-ray absorption value of density and atomic number is determined in the instance of a second X-ray spectrum. Based on a recording of a first distribution of X-ray absorption values of the object to be examined in the instance of a first X-ray spectrum, and on a recording of at least one second distribution of X-ray absorption values of the object to be examined in the instance of a second X-ray spectrum, the values for density and atomic number are determined by comparing the functional dependency of a first X-ray absorption value of the first distribution of X-ray absorption values with the functional dependency(ies) of the X-ray absorption values, which are assigned to the first X-ray absorption value, of the second and/or other distributions of X-ray absorption values.

Claims

1. A method for determining the distributions of density and atomic number in an object to be examined, comprising:

recording a first distribution of X-ray absorption values of the object to be examined for a first X-ray spectrum, and recording at least a second distribution of X-ray absorption values of the object to be examined for a second X-ray spectrum;

determining a first functional dependence recorded first distribution, of a first X-ray absorption value of the first distribution of X-ray absorption values on density and atomic number;

determining at least a second functional dependence, from the recorded second distribution, of a second X-ray absorption value, assigned to the first X-ray absorption value, of the second distribution of X-ray absorption values on density and atomic number; and

ascertaining a value for the density and the atomic number from a comparison of the first functional dependence with at least one of the second functional dependence and at least one further functional dependence.

2. The method as claimed in claim 1, wherein the determination of the functional dependence of the X-ray absorption values on density and atomic number is performed for at least one X-ray spectrum using a reference measurement on a calibration sample.

3. The method as claimed in claim 1 wherein the determination of the functional dependence of the X-ray absorption values on density and atomic number is performed for at least one X-ray spectrum in the form of a simulation on the basis of a physical model.

4. The method as claimed in claim 1, wherein a transformation of the distributions of the X-ray absorption values into a distribution of the density and a distribution of the atomic number for each of the assigned X-ray absorption values of the first distribution of the X-ray absorption values, and of the further distributions of the X-ray absorption values, is undertaken on the basis of the ascertainment of a value pair for density and atomic number such that the value pair fulfils the determined functional dependences of the X-ray absorption on density and atomic number for the first X-ray spectrum and at least one further X-ray spectrum.

5. The method as claimed in claim 1, wherein the first X-ray spectrum has a quantum energy that promotes an X-ray absorption relative to the quantum energy of the second X-ray spectrum by the photoeffect.

6. The method as claimed in claim 1, wherein at least one least one operating parameter of the X-ray tube and the detector characteristic is varied in order to vary an X-ray spectrum for recording the object to be examined.

7. The method as claimed in claim 1, wherein at least a subregion of the object to be examined is recorded with an increased X-ray dose.

13. The method as claimed in claim 2, wherein the determination of the functional dependence of the X-ray absorption values on density and atomic number is performed for at least one X-ray spectrum in the form of a simulation on the basis of a physical model.

14. The method as claimed in claim 2, wherein a transformation of the distributions of the X-ray absorption values into a distribution of the density and a distribution of the atomic number for each of the assigned X-ray absorption values of the first distribution of the X-ray absorption values, and of the further distributions of the X-ray absorption values, is undertaken on the basis of the ascertainment of a value pair for density and atomic number such that the value pair fulfils the determined functional dependences of the X-ray absorption on density and atomic number for the first X-ray spectrum and at least one further X-ray spectrum.

15. The method as claimed in claim 2, wherein the first X-ray spectrum has a quantum energy that promotes an X-ray absorption relative to the quantum energy of the second X-ray spectrum by the photoeffect.

16. The method as claimed in claim 2, wherein at least one of at least one operating parameter of the X-ray tube and the detector characteristic is varied in order to vary an X-ray spectrum for recording the object to be examined.

17. The method as claimed in claim 2, wherein at least a subregion of the object to be examined is recorded with an increased X-ray dose.

28. A computer-readable medium having code portions embodied thereon that, when read by a computer device, cause the computer device to perform the method of claim 1.

29. A computer software product having code portions embodied thereon that, when read by a computer device, cause the computer device to perform the method of claim 1.

8. An X-ray apparatus for ascertaining distributions of density and atomic number in an object to be examined, comprising:

an X-ray source adapted to emit X-radiation;

an X-ray detector adapted to detect the X-radiation emitted by the X-ray source, and for adapted to convert the X-radiation into electrical signals for further processing; and

a signal processing device, adapted to process the electrical signals of the X-ray detector, wherein the signal processing device is adapted to determine distributions of density and atomic number in an object to be examined, on the basis of at least two distributions of an X-ray absorption of the object to be examined, recorded with different X-ray spectra.

9. The X-ray apparatus as claimed in claim 8, wherein the X-ray source is adapted to emit a first X-ray spectrum in a first operating state and a second X-ray spectrum, different from the first operating state, in a second operating state.

10. The X-ray apparatus as claimed in claim 8, wherein the X-ray detector is adapted to convert spectral subregions of the X-radiation received from the X-ray source into mutually independent electrical signals.

11. The X-ray apparatus as claimed in claim 8 wherein a material is adapted to be introduced into the beam path of the X-radiation to record a first distribution of an X-ray absorption of the object to be examined, and no corresponding material is introduced into the beam path of the X-radiation to record a second distribution of an X-ray absorption of the object to be examined.

18. The X-ray apparatus as claimed in claim 9, wherein the X-ray detector is adapted to convert spectral subregions of the X-radiation received from the X-ray source into mutually independent electrical signals.

19. The X-ray apparatus as claimed in claim 9, wherein a material is adapted to be introduced into the beam path of the X-radiation to record a first distribution of an X-ray absorption of the object to be examined, and no corresponding material is introduced into the beam path of the X-radiation to record a second distribution of an X-ray absorption of the object to be examined.

20. The X-ray apparatus as claimed in claim 10, wherein a material is adapted to be introduced into the beam path of the X-radiation to record a first distribution of an X-ray absorption of the object to be examined, and no corresponding material is introduced into the beam path of the X-radiation to record a second distribution of an X-ray absorption of the object to be examined.

12. A computer software product for, in conjunction with a computer device, ascertaining the distributions of density and atomic number in an object (503) to be examined, on the basis of at least two image data records, recorded for different X-ray spectra, of the distribution of X-ray absorption values in the object to be examined.

21. An X-ray apparatus for ascertaining distributions of density and atomic number in an object to be examined, comprising:

means for emitting X-radiation;

means for detecting the emitted X-radiation and for converting the X-radiation into electrical signals for further processing; and

means for processing the electrical signals and for determining distributions of density and atomic number in an object to be examined, on the basis of at least two distributions of an X-ray absorption of the object to be examined, recorded with different X-ray spectra.

22. The X-ray apparatus as claimed in claim 21, wherein the means for emitting is for emitting a first X-ray spectrum in a first operating state and a second X-ray spectrum, different from the first operating state, in a second operating state.

23. The X-ray apparatus as claimed in claim 21, wherein the means for detecting is for converting spectral subregions of the X-radiation into mutually independent electrical signals.

24. The X-ray apparatus as claimed in claim 21, wherein a material is adapted to be introduced into the beam path of the X-radiation to record a first distribution of an X-ray absorption of the object to be examined, and no corresponding material is introduced into the beam path of the X-radiation to record a second distribution of an X-ray absorption of the object to be examined.

25. The X-ray apparatus as claimed in claim 21, wherein the means for emitting includes an x-ray source.

26. The X-ray apparatus as claimed in claim 21, wherein the means for detecting includes an x-ray detector.

27. A method for ascertaining distributions of density and atomic number in an object to be examined, comprising:

detecting emitted X-radiation;

converting the X-radiation into electrical signals; and

determining distributions of density and atomic number in an object to be examined, on the basis of at least two distributions of an X-ray absorption of the object to be examined, recorded with different X-ray spectra.

30. A computer-readable medium having code portions embodied thereon that, when read by a computer device, cause the computer device to perform the method of claim 27.

31. A computer software product having code portions embodied thereon that, when read by a computer device, cause the computer device to perform the method of claim 27.