Coincidence-enabling photon-counting detector
The present approach relates to the use of energy-resolved, photon-counting detectors, such as CZT- or CdTe-based detectors, to acquire spectral information that is not available with conventional energy-integrating detectors. In certain embodiments, the present approach discussed reduces or eliminates spectral contamination incurred by transient signals in neighboring pixels in designs employing coincidence logic and shaping amplifiers with short shaping times.
1. A detector readout circuit, comprising:
a charge-sensitive amplifier, comprising:
an amplifier configured to receive an input signal from a radiation detector and to output an amplified signal;
a reset switch configured to receive a reset signal; and
a capacitor in electrical connection with the reset switch and amplifier;
a shaping amplifier configured to receive the amplified signal and perform a shaping operation on the amplified signal to generate a shaped signal, wherein the shaping operation has a shaping time on the order of 50 ns or less;
energy readout and control circuitry configured to receive the shaped signal from the shaping amplifier, the circuitry comprising:
an integrator configured to receive the shaped signal and to integrate the shaped signal over time to generate an integrated signal;
a comparator configured to receive the integrated signal and determine a true detection event such that the integrated signal is greater than a preset threshold, and
a peak analog-to-digital converter configured to receive inputs signals from the comparator and the shaping amplifier and to output energy information of a detected true event;
a delay circuit configured to receive an output from the comparator and to generate a delay signal to operate the reset switch of the charge-sensitive amplifier.
2. The detector circuit of claim 1 , wherein the shaping amplifier is a fast shaping amplifier and has a shaping time of approximately 20 ns or less.
3. The detector circuit of claim 1 , wherein the integrator integrates the shaped signal over a time window of approximately 10 ns to 40 ns.
4. The detector circuit of claim 1 , wherein the integrator integrates the shaped signal over a time window so as to differentiate the true event signal from a transient signal if present.
5. The detector circuit of claim 1 , further comprising:
a clock circuit; and
a timing stamp circuit in communication with the clock circuit and configured to receive the timing output and generate a hit trigger in response.
6. The detector circuit of claim 5 , wherein the hit trigger corresponds to a time-stamped for the detection event.
7. The detector circuit of claim 1 , further comprising:
a capacitor-resistor shaper configured to receive the amplified signal and to generate a timing output.
8. The timing stamp circuit of claim 5 , wherein the input signal for the timing stamp circuitry is generated by at least one of an output signal of a capacitor-resistor shaper circuit operating on the amplified signal, the shaping amplifier, or the comparator.
9. A method for processing a detector signal from an energy-resolved photon-counting radiation detector, the method comprising:
receiving the detector signal at an amplifier and outputting an amplified signal;
performing a shaping operation on the amplified signal to generate a shaped signal, wherein the shaping operation has a shaping time of 50 ns or less;
receiving the shaped signal at an integrator configured to integrate the shaped signal over time to generate an integrated signal;
comparing the integrated signal to a threshold and outputting a signal indicating that the integrated signal is greater than the threshold;
performing a peak analog-to-digital conversion based on the output of the comparison of the integrated signal to a threshold, and on the shaped signal to generate energy information of the detected event.
10. The method of claim 9 , further comprising:
based on the output of the comparison, generating a delay signal and resetting operation of the amplifier using the delay signal.
11. The method of claim 9 , further comprising:
receiving the amplified signal at a capacitor-resistor (CR) shaper and generating a CR shaper output.
12. The method of claim 9 , further comprising:
generating a timing signal based upon at least of one a capacitor-resistor shaper signal using the amplified signal as input, the shaped signal, or the output signal indicating that the integrated signal is greater than the threshold, and also a clock signal.
13. The method of claim 9 , wherein the shaping operation has a shaping time of approximately 20 ns or less.
14. The method of claim 9 , wherein the integrator integrates the shaped signal over a time window of approximately 10 ns to 40 ns.
15. The method of claim 9 , wherein the integrator integrates the shaped signal over a time window so as to discriminate a transient signal if present.
16. An imaging system, comprising:
an X-ray source configured to emit X-rays;
an energy-resolved photon-counting detector, comprising an array of detector pixels wherein each detector pixel is connected to a detector circuit, comprising:
a charge-sensitive amplifier, comprising:
an amplifier configured to receive as an input readout signals from the photon-counting, energy discriminating radiation detector and to output an amplified signal;
a reset switch configured to receive a reset signal; and
a capacitor in electrical communication with the reset switch and amplifier;
a shaping amplifier configured to receive the amplified signal and perform a shaping operation on the amplified signal to generate a shaped signal;
energy readout and control circuitry configured to receive the shaped signal from the shaping amplifier, the circuitry comprising:
an integrator configured to receive the shaped signal and to integrate the shaped signal over a time interval to generate an integrated signal;
a comparator configured to receive the integrated signal and determine a true detection event based on the comparison between the integrated signal and a threshold, and
a peak analog-to-digital converter configured to receive the amplified signal from the shaping amplifier and to output energy information for the true detected event based on the control signal from the comparator;
a delay circuit configured to receive an output from the comparator and to generate a delay signal to operate the reset switch of the charge-sensitive amplifier; and
image processing circuitry configured to receive at least the energy measurements of the peak analog-to-digital converter and to generate an image based on the energy measurements.
17. The imaging system of claim 16 , wherein the energy-resolved photon-counting detector is manufactured with a semiconductor material, such as cadmium zinc telluride or cadmium telluride.
18. The imaging system of claim 16 , wherein the shaping amplifier has a shaping time of approximately 20 ns or less.
19. The imaging system of claim 16 , wherein the integrator integrates the shaped signal over a time window of approximately 10 ns to 40 ns.
20. The imaging system of claim 16 , wherein the detector circuit further comprises:
a capacitor-resistor (CR) shaper configured to receive the amplified signal and to generate a timing output.
21. The imaging system of claim 16 , wherein the detector circuit further comprises:
a clock circuit; and
a timing stamp circuit in communication with the clock circuit and configured to receive the timing output and generate a hit trigger in response.