Scatter correction technique for use with a radiation detector
The present approach relates to scatter correction of signals acquired using radiation detectors on a pixel-by-pixel basis. In certain implementations, the systems and methods disclosed herein facilitate scatter correction for signals generated using a detector having segmented detector elements, such as may be present in an energy-resolving, photon-counting CT imaging system.
1. A method for reducing scatter signal in a computed tomography (CT) system comprising an X-ray source and a pixelated detector, the method comprising:
for each respective segment of a detector element comprising a plurality of segments disposed at a plurality of depths with respect to the surface of the detector element facing the X-ray source, acquiring a respective response signal;
for the detector element, estimating a scatter signal at one or more segments of the detector element based on an acceptance angle of the respective segment of the detector element, wherein the acceptance angle depends on the depth of the respective segment of the detector element; and
based upon the estimated scatter signal, estimating a primary signal substantially free of scatter at one or more segments of the plurality of segments to generate scatter-corrected readout signals.
2. The method of claim 1 , wherein the primary signal is estimated based upon a respective readout signal from a respective segment furthest from the X-ray source.
3. The method of claim 1 , wherein the primary signal and the scatter signal are jointly estimated using the readout signals from all segments of the detector element, with readout signals from segments further from the X-ray source receiving greater weighting in the joint estimation process.
4. The method of claim 1 , wherein the act of estimating the scatter signal is based upon one or both of dimensions of an imaged object or the geometry of the X-ray source and detector.
5. The method of claim 1 , wherein the act of estimating the scatter signal is based upon a respective X-ray spectrum estimated for each segment of the detector element.
6. The method of claim 1 , wherein the act of estimating comprises applying a least square fitting operation.
7. The method of claim 1 , wherein the act of estimating employs a physics-based scatter model to estimate the scatter signal at the other segments of the detector element.
8. The method of claim 7 , wherein the physics based scatter model includes a parameter for the receiving angle for each of the segments of the detector element.
9. The method of claim 1 , further comprising smoothing the estimated scatter signal.
10. The method of claim 1 , wherein the act of estimating is performed on averaged measured signals from corresponding segments of adjacent detector elements.
11. The method of claim 1 , wherein the acceptance angle (θ) of the respective segment of the detector element is characterized as [θ α tan −1 (w/d)], where w is the width of the detector element and d is the depth of the respective segment.
12. The method of claim 1 , wherein the ratio of the primary signal of a segment of the detector element (P i ) with respect to the primary signal of the bottommost segment (P 1 ) of the detector element is given as:
P
i
P
1
=
e
μ
(
E
)
(
d
i
+
…
+
d
2
)
(
1
-
e
-
μ
(
E
)
d
i
)
1
-
e
-
μ
(
E
)
d
2
where i is a number of the segment of the detector element with respect to the bottommost segment, d is the depth of the respective segment and μ(E) is an X-ray attenuation coefficient of the detector element material for X-rays of energy E.
13. A computed tomography (CT) imaging system, comprising:
an X-ray radiation source configured to emit X-ray radiation;
a pixelated detector configured to generate X-ray signals in response to the emitted X-ray radiation, wherein the pixelated detector comprises a plurality of detector elements, each detector element comprising a plurality of segments offset in the direction of X-ray radiation propagation at a plurality of depths, wherein at least a portion of the detector elements are separated by X-ray radiation blocking plates in at least one dimension;
a processing component configured to receive X-ray signals read out from the pixelated detector, wherein an X-ray signal is read out for each segment of each detector element, and wherein for each detector element the processing component:
estimates a scatter signal at one or more segments of the detector element based on an acceptance angle of the respective segment of the detector element, wherein the acceptance angle depends on the depth of the respective segment of the detector element
based upon the estimated scatter signal, estimates a primary signal substantially free of scatter at one or more segments of the plurality of segments to generate scatter-corrected readout signals; and
for the combined scatter corrected readout signals from each detector element, reconstructs an image using the scatter corrected readout signals.
14. The CT imaging system of claim 13 , wherein the primary signal and the scatter signal are jointly estimated using the readout signals from all segments of the detector element.
15. The CT imaging system of claim 14 , where the readout signals from segments further from the X-ray radiation source have less scatter signal which can be modeled using the depth of the segment as one parameter.
16. The CT imaging system of claim 13 , wherein the primary signal is estimated based upon a respective readout signal from a respective segment furthest from the X-ray radiation source.
17. The CT imaging system of claim 13 , wherein the detector elements are separated by X-ray radiation blocking plates in intervals of every pixel, every second pixel, every third pixel, every fourth pixel, or every fifth pixel.
18. The CT imaging system of claim 13 , wherein the processing component is further configured to estimate the scatter signal based upon one or both of dimensions of an imaged object or the geometry of the X-ray source and detector.
19. The CT imaging system of claim 13 , wherein the processing component is further configured to estimate the scatter signal based upon a respective X-ray spectrum estimated for each segment of the detector element.
20. The CT imaging system of claim 13 , wherein the processing component is further configured to estimate the scatter signal using averaged measured X-ray signals from corresponding segments of adjacent detector elements.