Focus/detector system of an X-ray apparatus for generating phase contrast recordings
A focus/detector system of an X-ray apparatus is disclosed, for generating projective or tomographic phase contrast recordings. The system, in at least one embodiment, includes at least of a beam source, having a focus and a focus-side source grating, arranged in the beam path and to generate a field of ray-wise coherent X-rays, and a detector arrangement having a multiplicity of grating/detector modules arranged next to one another. The detector arrangement, in at least one embodiment, which respectively include, arranged successively in the beam direction, at least one phase grating for generating a first interference pattern, an analysis grating for generating a further interference pattern, and detector elements arranged flat. The individual grating lines of all gratings are aligned mutually parallel.
1. A focus/detector system of an X-ray apparatus for generating at least one of projective and tomographic phase contrast recordings, the system comprising:
a beam source, including a focus and a focus-side source grating, arranged in the beam path to generate a field of ray-wise coherent X-rays; and
a detector arrangement including a multiplicity of grating/detector modules arranged next to one another, which respectively comprise arranged successively in the beam direction:
at least one phase grating to generate a first interference pattern,
an analysis grating to generate a further interference pattern, and
detector elements arranged flat, the individual grating lines of all gratings being aligned mutually parallel.
2. The focus/detector system as claimed in claim 1 , wherein the grating surfaces formed by the grating lines on the phase and analysis gratings of the module are aligned mutually parallel.
3. The focus/detector system as claimed in claim 1 , wherein the grating surfaces are respectively aligned perpendicularly to a ray which extends from the focus to the grating/detector module and intersects the grating surfaces.
4. The focus/detector system as claimed in claim 3 , wherein the ray which respectively intersects the grating surfaces perpendicularly is the central ray which intersects the grating surfaces at their respective midpoint.
5. The focus/detector system as claimed in claim 4 , wherein the grating/detector modules are arranged so that the midpoints of all phase grating surfaces have the same distance from the focus.
6. The focus/detector system as claimed in claim 4 , wherein the grating/detector modules are arranged so that the midpoints of all analysis grating surfaces have the same distance from the focus.
7. The focus/detector system as claimed in claim 4 , wherein the grating/detector modules are arranged so that the midpoints of all analysis grating surfaces have the same distance from the focus.
8. The focus/detector system as claimed in claim 4 , wherein the grating/detector modules are arranged so that the midpoints of all detector surfaces, consisting of the sum of detector elements arranged flat, have the same distance from the focus.
9. The focus/detector system as claimed in claim 4 , wherein the phase grating surfaces are respectively formed on a spherical surface segment with the focus as the midpoint.
10. The focus/detector system as claimed in claim 9 , wherein the analysis grating surfaces are respectively formed on a spherical surface segment with the focus as the midpoint.
11. The focus/detector system as claimed in claim 4 , wherein the analysis grating surfaces are respectively formed on a spherical surface segment with the focus as the midpoint.
12. The focus/detector system as claimed in claim 4 , wherein the detector surfaces of a grating/detector module, consisting of the sum of detector elements arranged flat, respectively extend over a spherical surface segment with the focus as the midpoint.
13. The focus/detector system as claimed in claim 1 , wherein at least one device is provided for relative displacement of at least one analysis grating with respect to the phase gratings perpendicularly to the beam direction and perpendicularly to the longitudinal direction of the grating lines, which acts on at least two analysis gratings of at least two grating/detector modules.
14. The focus/detector system as claimed in claim 1 , wherein one device per grating/detector module is provided for relative displacement of the analysis grating of this grating/detector module with respect to the phase grating of this grating/detector module perpendicularly to the beam direction and perpendicularly to the longitudinal direction of the grating lines.
15. The focus/detector system as claimed in claim 1 , wherein the grating/detector modules are arranged in a checkerboard fashion as seen in projection from the focus.
16. The focus/detector system as claimed in claim 1 , wherein the grating/detector modules form a single line as seen in projection from the focus.
17. The focus/detector system as claimed in claim 1 , wherein the grating/detector modules are designed and arranged so that each grating/detector module and its grating arrangement satisfies the following geometrical conditions:
p
0
=
p
2
×
l
d
,
p
1
=
2
×
p
0
×
p
2
p
0
+
p
2
d
=
l
×
d
≡
l
-
d
≡
with
d
≡
=
1
2
×
(
p
1
2
4
λ
)
,
h
1
=
λ
2
(
n
-
1
)
.
where:
p 0 =grating period of the source grating G 0 ,
p 1 =grating period of the phase grating G 1 ,
p 2 =grating period of the analysis grating G 2 ,
d=distance from the phase grating G 1 to the analysis grating G 2 in fan beam geometry,
d ≡ =distance from the phase grating G 1 to the analysis grating G 2 with parallel geometry,
l=distance from the source grating G 0 to the phase grating G 1 ,
λ=selected wavelength of the radiation,
h 1 =bar height of the phase grating G 1 in the beam direction,
n=refractive index of the grating material of the phase grating.
18. An X-ray system for generating projective phase contrast recordings including at least one focus/detector system as claimed in claim 1 .
19. The X-ray system as claimed in claim 18 , wherein a computation unit is provided for controlling the analysis grating and calculating the phase shift from a plurality of intensity measurements of the same beam with differently offset analysis gratings.
20. An X-ray C-arc system for generating projective and tomographic phase contrast recordings including at least one focus/detector system as claimed in claim 1 , arranged on a C-arc rotatable about a subject.
21. An X-ray CT system for generating tomographic phase contrast recordings including at least one focus/detector system as claimed in claim 1 , arranged on a gantry rotatable about a subject.
22. A method for generating tomographic recordings of a subject, the method comprising:
scanning the subject at least one of circularly and spirally with at least one modularly constructed focus/detector system a phase shift of rays passing through the subject being determined by at least three intensity measurements with analysis gratings respectively arranged offset;
interpolating the phase shift using neighboring values for rays which cannot be measured or cannot be measured accurately due to the modular construction of the detector; and
reconstructing tomographic phase contrast recordings using the rays' phase shifts measured and determined by interpolation; wherein the focus/detector system includes,
a beam source, including a focus and a focus-side source grating, arranged in the beam path to generate a field of ray-wise coherent X-rays; and
a detector arrangement including a multiplicity of grating/detector modules arranged next to one another, which respectively comprise arranged successively in the beam direction:
at least one phase grating to generate a first interference pattern,
an analysis grating to generate a further interference pattern, and
detector elements arranged flat, the individual grating lines of all gratings being aligned mutually parallel.
23. A storage medium of an X-ray system, the storage medium containing program code that, when executed, carries out the method as claimed in claim 22 during operation of the X-ray system.
24. An X-ray system for generating projective phase contrast recordings, comprising:
at least one focus/detector system for generating at least one of projective and tomographic phase contrast recordings, the system including,
a beam source including a focus and a focus-side source grating, arranged in the beam path to generate a field of ray-wise coherent X-rays, and
a detector arrangement including a multiplicity of grating/detector modules arranged next to one another, which respectively comprise arranged successively in the beam direction:
at least one phase grating to generate a first interference pattern,
an analysis grating to generate a further interference pattern, and
detector elements arranged flat, the individual grating lines of all gratings being aligned mutually parallel; and
a computation and control unit, containing program code that, when executed on the computation and control unit, the computation and control unit is configured to,
scan the subject at least one of circularly and spirally with the at least one modularly constructed focus/detector system, the phase shift of the rays when passing through the subject being determined by at least three intensity measurements with analysis gratings respectively arranged offset,
interpolate, the phase shift using neighboring values for rays which cannot be measured or cannot be measured accurately owing to the modular construction of the detector, and
reconstruct tomographic phase contrast recordings using the rays' phase shifts measured and determined by interpolation.