Pixel-design for use in a radiation detector
The present approach relates to the use of reference pixels provided between the primary pixels of a detector panel. Coincidence circuitry or logic may be employed so that the measured signal arising from the same X-ray event may be properly, that is the signal measured at both a reference and primary pixel may be combined so as to provide an accurate estimate of the measured signal, at an appropriate location on the detector panel.
1. A radiation detector assembly comprising:
an array of primary pixels;
an array of reference pixels, wherein each reference pixel is adjacent to at least one primary pixel;
detection circuitry in communication with the array of primary pixels and the array of reference pixels, wherein the detection circuitry is configured to detect signals in the primary pixels and the reference pixels that are coincident in time; and
an anti-scatter collimator positioned over the array of reference pixels.
2. The radiation detector assembly of claim 1 , wherein the anti-scatter collimator comprising X-ray attenuating septa arranged in a one-dimensional or two-dimensional geometry.
3. The radiation detector assembly of claim 1 , wherein the reference pixels are smaller in area than the primary pixels.
4. The radiation detector assembly of claim 1 , wherein the detection circuitry is further configured to combine signals determined to be coincident and measured in a reference pixel and a primary pixel that are adjacent to one another.
5. The radiation detector assembly of claim 4 , wherein combining the signals comprises summing the signals.
6. The radiation detector assembly of claim 1 , the detection circuitry is further configured to detect signals that are coincident in time in response to a signal being detected in a reference pixel.
7. The radiation detector assembly of claim 6 , wherein the signal from the reference pixel exceeds a noise threshold to trigger detection of the signals that are coincident in time.
8. The radiation detector assembly of claim 1 , wherein width of the reference pixels is less than or equal to half width of the primary pixels such that a count rate in the reference pixels is substantially less than a count rate in the primary pixels when exposed to same flux of X-rays.
9. The radiation detector assembly of claim 1 , wherein width of the reference pixels corresponds to diameter of a charge cloud induced by X-ray interaction with a semiconductor sensor of the radiation detector assembly.
10. The radiation detector assembly of claim 1 , wherein the detection circuitry is configured to associate an output signal of the detection circuitry with a respective reference pixel or a respective primary pixel depending on whether the coincident signals are detected.
11. The radiation detector assembly of claim 1 , wherein the detection circuitry comprises a first type of channel for the primary pixels and a second type of channel for the reference pixels.
12. The radiation detector assembly of claim 1 , wherein the detection circuitry comprises a respective channel for each primary pixel and each reference pixel, and wherein each channel comprises at least one threshold comparator and an associated digital counter, and wherein the detection circuitry is configured to increment the digital counter when an X-ray-induced signal exceeds a threshold of the respective comparator.
13. The radiation detector assembly of claim 1 , wherein the detection circuitry comprises a respective channel for each primary pixel and each reference pixel, and wherein each channel comprises a peak detection circuit and an analog-to-digital converter configured to output a digital signal representative of an X-ray-induced signal.
14. The radiation detector assembly of claim 1 , wherein the detection circuitry is configured to produce sub-pixel spatial resolution by combining signals from a respective primary pixel and an adjacent reference pixel to produce an output representative of relative position of an absorbed X-ray between the respective primary pixel and the adjacent reference pixel.
15. The radiation detector assembly of claim 14 , wherein the relative position of the absorbed X-ray is determined based on a proportion of the signals induced in the respective primary pixel and the adjacent reference pixel.
16. A method for detecting and correcting a charge-sharing event in a radiation detector, comprising:
reading out signals from an array of primary pixels and an array of reference pixels, wherein each reference pixel is adjacent to at least one primary pixel, and wherein the array of reference pixels is positioned under an anti-scatter collimator;
detecting a signal read out from a respective reference pixel;
executing coincidence logic to identify a respective primary pixel adjacent to the respective reference pixel in which the corresponding signal was read out; and
combining the signal from the respective reference pixel and the corresponding signal.
17. The method of claim 16 , wherein the reference pixels are smaller in area than the primary pixels.
18. The method of claim 16 , wherein combining the signal and the corresponding signal comprises summing the signal and the corresponding signal.
19. The method of claim 16 , wherein detecting the signal read out from the respective reference pixel comprises comparing the signal to a noise threshold.
20. The method of claim 16 , further comprising determining a sub-pixel spatial resolution based on a proportion of the signal to the corresponding signal.