Method for generating a virtual X-ray projection on the basis of an image data set obtained with an X-ray imaging device, computer program, data carrier and X-ray imaging device
An embodiment relates to a method for generating a virtual X-ray projection of at least one body region of a patient to be imaged with an X-ray imaging device, a machine-readable data carrier and/or an X-ray imaging device. The method includes acquiring at least one projection data set representing the at least one body region of the patient to be imaged; reconstructing an image data set from the at least one projection data set, the image data set representing local X-ray attenuation values in the at least one body region; replacing at least one local X-ray attenuation value by a modified X-ray attenuation value; forward projecting the modified image data set onto a virtual X-ray radiation detector; calculating intensity values for a plurality of detector elements from the modified projection data set; transforming the calculated intensity values into scan values; and assigning the scan values to an image matrix.
1. A method for forming a virtual X-ray projection of at least one body region of a patient to be imaged with an X-ray imaging device, the method comprising:
acquiring at least one projection data set, representing the at least one body region of the patient to be imaged, with the X-ray imaging device;
reconstructing an image data set from the at least one projection data set, wherein the image data set represents local X-ray attenuation values in the at least one body region of the patient to be imaged;
modifying the image data set such that at least one local X-ray attenuation value is replaced by a modified X-ray attenuation value;
generating a modified projection data set by forward projection of the modified image data set onto a virtual X-ray radiation detector, taking account of a virtual projection geometry;
calculating intensity values for a plurality of detector elements of the virtual X-ray radiation detector from the modified projection data set, taking account of the virtual projection geometry;
transforming the calculated intensity values into scan values output by the virtual X-ray radiation detector; and
forming the virtual X-ray projection by assigning the scan values to an image matrix, wherein the transforming of the calculated intensity values into the scan values takes account of a signal characteristic line of the virtual X-ray radiation detector.
2. The method of claim 1 , wherein the modifying of the image data set comprises assigning the at least one local X-ray attenuation value to a material class and substitution thereof with a modified X-ray attenuation value corresponding to the material class.
3. The method of claim 2 wherein, the at least one local X-ray attenuation value is assigned to one of the following material classes: bone, soft tissue, or contrast medium.
4. The method of claim 3 , wherein at least one of the modified X-ray attenuation values corresponding to one material class is 0.
5. The method of claim 3 , wherein at least one of the modified X-ray attenuation values corresponding to one material class is selected depending on a virtual X-ray quantum energy distribution.
6. The method of claim 2 , wherein at least one of the modified X-ray attenuation values corresponding to one material class is 0.
7. The method of claim 2 , wherein at least one of the modified X-ray attenuation values corresponding to one material class is selected depending on a virtual X-ray quantum energy distribution.
8. The method of claim 7 , wherein at least two local X-ray attenuation values are each replaced with a modified X-ray attenuation value which is selected depending on at least one pre-determinable virtual X-ray quantum energy distribution, and wherein the at least one pre-determinable virtual X-ray quantum energy distribution includes at least two pre-determinable virtual X-ray quantum energy distributions, and wherein the at least two pre-determinable virtual X-ray quantum energy distributions differ from one another.
9. The method of claim 1 , wherein the modifying of the image data set comprises determination of a material composition in at least one part of the body region of the patient to be imaged.
10. The method of claim 9 , wherein the determination of the material composition takes place based upon at least two projection data sets acquired via the X-ray imaging device, each of the at least two projection data sets being acquired according to a different previously stipulated X-ray quantum energy distribution.
11. The method of claim 10 , wherein the modifying of the image data set comprises assigning the at least one local X-ray attenuation value to a material class and substitution thereof with at least one modified X-ray attenuation value corresponding to the material class and wherein the at least one modified X-ray attenuation value is determined depending on a pre-determinable virtual X-ray quantum energy distribution and the determined material composition.
12. The method of claim 9 , wherein the modifying of the image data set comprises assigning the at least one local X-ray attenuation value to a material class and substitution thereof with at least one modified X-ray attenuation value corresponding to the material class and wherein the at least one modified X-ray attenuation value is determined depending on a pre-determinable virtual X-ray quantum energy distribution and the determined material composition.
13. The method of claim 12 , wherein at least two local X-ray attenuation values are each replaced with a modified X-ray attenuation value which is selected depending on at least one pre-determinable virtual X-ray quantum energy distribution, and wherein the at least one pre-determinable virtual X-ray quantum energy distribution includes at least two pre-determinable virtual X-ray quantum energy distributions, and wherein the at least two pre-determinable virtual X-ray quantum energy distributions differ from one another.
14. The method of claim 1 , wherein the virtual projection geometry assumes parallel virtual X-ray beams or conical virtual X-ray beams.
15. The method of claim 14 , wherein the forward projection comprises generating line integrals L i,j over the X-ray attenuation values of the modified image data set along a plurality of virtual X-ray beams through the body region of the patient to be imaged by way of raytracing methods or Fourier methods.
16. The method of claim 15 , wherein the calculating of the intensity values is carried out according to the rule
I i,j =I 0;i,j *exp(− L i,j )*cos(β i,j )
and wherein indices i,j refer to row and column of a detector element [i,j] of the virtual X-ray radiation detector, β i,j is an angle between an observed X-ray beam to the detector element [i,j] and the surface normals n of the virtual X-ray radiation detector and I 0;i,j is an X-ray radiation intensity incident upon the detector element [i,j] without X-ray attenuation caused by the patient.
17. The method of claim 1 , wherein the forward projection is carried out taking account of one or more parameters representing a virtual scan process.
18. The method of claim 17 , wherein the calculating of the intensity values is carried out according to the rule
I i,j =I 0;i,j *exp(− L i,j )*cos(β i,j )
and wherein indices i,j refer to row and column of a detector element [i,j] of the virtual X-ray radiation detector, β i,j is an angle between an observed X-ray beam to the detector element [i,j] and the surface normals n of the virtual X-ray radiation detector and I 0;i,j is an X-ray radiation intensity incident upon the detector element [i,j] without X-ray attenuation caused by the patient.
19. The method of claim 1 wherein, on calculating of the intensity values, at least one of cross-talk behavior of the virtual X-ray radiation detector and scattered radiation effects are taken into account.
20. The method of claim 1 , wherein the reconstructing of the image data set takes place with a spatial resolution in a range of 0.1 mm to 0.5 mm.
21. The method of claim 1 , wherein the scan values are represented in the image matrix as gray values.
22. A non-transitory computer readable medium including computer code which, when executed on a computer, is configured to carry out the method of claim 1 .
23. A non-transitory machine-readable data carrier including computer code which, when executed on a computer device, is configured to carry out the method of claim 1 .
24. An X-ray imaging device for generating a virtual X-ray projection of at least one body region of a patient to be imaged, the X-ray imaging device comprising:
an X-ray radiation module including at least one X-ray radiation source to generate and emit X-ray radiation with, for each at least one X-ray radiation source, a determinable X-ray quantum energy distribution;
a detector module including at least one X-ray radiation detector to detect X-ray radiation emitted by the X-ray radiation module; and
a computer system configured to, during operation, at least
acquire at least one projection data set, representing the at least one body region of the patient to be imaged, with the X-ray imaging device,
reconstruct an image data set from the at least one projection data set, wherein the image data set represents local X-ray attenuation values in the at least one body region of the patient to be imaged,
modify the image data set such that at least one local X-ray attenuation value is replaced by a modified X-ray attenuation value,
generate a modified projection data set by forward projection of the modified image data set onto a virtual X-ray radiation detector, taking account of a virtual projection geometry,
calculate intensity values for a plurality of detector elements of the virtual X-ray radiation detector from the modified projection data set, taking account of the virtual projection geometry,
transform the calculated intensity values into scan values output by the virtual X-ray radiation detector taking account of a signal characteristic line of the virtual X-ray radiation detector, and
form the virtual X-ray projection by assigning the scan values to an image matrix.
25. The X-ray imaging device of claim 24 , wherein the X-ray module comprises at least two X-ray radiation sources to generate and emit X-ray radiation, each a determinable X-ray quantum energy distribution, and wherein the detector module comprises at least two X-ray radiation detectors, to respectively detect X-ray radiation emitted by one of the at least two X-ray radiation sources.
26. The X-ray imaging device of claim 24 , wherein the at least one X-ray radiation detector is selective for the energy of incident X-ray quanta.
27. The X-ray imaging device of claim 24 , wherein the at least one X-ray radiation detector is configured as a planar detector.
28. An X-ray imaging device for generating a virtual X-ray projection of at least one body region of a patient to be imaged, the X-ray imaging device comprising:
an X-ray radiation module comprising at least one X-ray radiation source to generate and emit X-ray radiation with, for each at least one X-ray radiation source, a determinable X-ray quantum energy distribution, and
a detector module comprising at least one X-ray radiation detector to detect X-ray radiation emitted by the X-ray radiation module, and
a computer system, comprising
an interface, configured to acquire at least one projection data set representing at least one body region of a patient to be imaged,
at least one processor configured to
reconstruct an image data set from the at least one projection data set, wherein the image data set represents local X-ray attenuation values in the at least one body region of the patient to be imaged,
modify the image data set such that at least one local X-ray attenuation value is replaced by a modified X-ray attenuation value,
generate a modified projection data set by forward projection of the modified image data set onto a virtual X-ray radiation detector, taking account of a virtual projection geometry,
calculate intensity values for a plurality of detector elements of the virtual X-ray radiation detector from the modified projection data set taking account of the virtual projection geometry,
transform the calculated intensity values into scan values output by the virtual X-ray radiation detector taking account of a signal characteristic line of the virtual X-ray radiation detector, and
assign the scan values to an image matrix.
29. The X-ray imaging device of claim 28 , wherein the X-ray module comprises at least two X-ray radiation sources to generate and emit X-ray radiation, each a determinable X-ray quantum energy distribution, and wherein the detector module comprises at least two X-ray radiation detectors, to respectively detect X-ray radiation emitted by one of the at least two X-ray radiation sources.
30. The X-ray imaging device of claim 28 , wherein the at least one X-ray radiation detector is selective for the energy of incident X-ray quanta.
31. The X-ray imaging device of claim 28 , wherein the at least one X-ray radiation detector is configured as a planar detector.