Phase contrast imaging apparatus
An x-ray imaging system includes an x-ray source, an x-ray detector including a plurality of detector strips arranged in a first direction of the x-ray detector. Each detector strip includes a plurality of detector pixels arranged in a second direction of the x-ray detector. A phase grating and a plurality of analyzer gratings including grating slits are disposed between the x-ray source and detectors. The x-ray source and the x-ray detector are adapted to perform a scanning movement in relation to an object in the first direction, in order to scan the object. Each of the plurality of analyzer gratings ( 162 ) is arranged in association with a respective detector strip with the grating slits arranged in the second direction. The grating slits of the analyzer gratings of the detector strips are offset relative to each other in the second direction.
1. An x-ray phase contrast imaging system comprising:
a scan arm configured to move with respect to an imaging region;
an x-ray source mounted to the scan arm;
an x-ray detector mounted to the scan arm opposite the imaging region from the x-ray source, the x-ray detector including a plurality of detector strips arranged in a first direction of the x-ray detector, each detector strip further comprising a plurality of detector pixels arranged in a second direction of the x-ray detector;
a phase grating disposed between the x-ray source and the x-ray detector;
a plurality of analyzer gratings comprising grating slits, the analyzer gratings being mounted between the imaging region and the x-ray detector and configured to move with the x-ray detector; and;
a controller configured to move the scan arm and the x-ray source and the x-ray detector in the first direction, in order to scan an object in the imaging region;
wherein each of the plurality of analyzer gratings is arranged in association with a respective one of the detector strips with the grating slits arranged in the second direction; and
wherein the grating slits of each analyzer grating offset in the second direction relative to the grating slits of other analyzer gratings.
2. The x-ray imaging system according to claim 1 , wherein the grating slits of the analyzer gratings are displaced such that the detector strips sample an entire fringe period of interference fringes generated by the phase grating and displaced by a phase gradient in the object when the object is scanned.
3. The x-ray imaging system according to claim 1 , wherein the grating slits of contiguous analyzer gratings are offset in the second direction in a systematic manner by a defined displacement distance d.
4. The x-ray imaging system according to claim 3 , wherein the displacement distance d is defined by
p
f
N
<
d
<
p
f
,
where p f is a fringe period, and N is the number of detector strips that cover the fringe period in its entirety.
5. The x-ray imaging system according to claim 3 , wherein the displacement distance d is
p
f
3
.
6. The x-ray imaging system according to claim 1 , wherein the grating slits of contiguous analyzer gratings offset relative to each other in the second direction in an arbitrary manner, wherein the arbitrary manner comprises a random displacement d.
7. The x-ray imaging system according to claim 1 , wherein adjacent analyzer gratings arbitrarily displaced relative to the detector strips in a first direction.
8. The x-ray imaging system according to claim 1 , further comprising:
a pre-collimator arranged between the analyzer grating and the phase grating and a post-collimator arranged between the analyzer grating and the x-ray detector.
9. The x-ray imaging system according to claim 8 , further comprising:
a source grating arranged between the x-ray source and the phase grating.
10. The x-ray imaging system according to claim 1 , wherein the detector is adapted to count photons impinging on the detector strips and generate a signal corresponding to energy of impinging photons, and further including: a control unit configured to receive said signals and assign a weight to the phase-contrast image effect based on an efficiency at each of a plurality of x-ray energies.
11. The x-ray imaging system according to claim 1 , wherein the analyzer gratings are each connected to a corresponding one of the detector strips by a snap-fit connection.
12. The x-ray imaging system according to claim 1 , wherein each analyzer grating comprises several smaller units, adapted to be connected to each other during the manufacturing of the analyzer gratings.