Circuit arrangement for counting X-ray radiation X-ray quanta by way of quanta-counting detectors, and also an application-specific integrated circuit and an emitter-detector system

1. A circuit arrangement for counting X-ray radiation X-ray quanta in detector elements in a detector in an emitter-detector system of an X-ray CT system, the X-ray radiation including a multiplicity of X-ray quanta that can have a maximum energy and wherein the X-ray quanta registered in each detector element generate a signal profile with X-ray-quanta-energy-dependent voltage pulses with different heights, which may be superposed on one another, the circuit arrangement, in each detector element, comprising:

at least one first comparator with a first energy threshold less than or equal to the maximum X-ray-quantum energy; and

at least one second comparator with a second energy threshold greater than the maximum X-ray-quantum energy, the at least one first comparator and at least one second comparator being connected to the detector element, wherein the at least one first comparator and at least one second comparator each respectively generate a comparator output signal if their respective energy threshold is exceeded, the at least one first comparator and at least one second comparator including a logical interconnection, wherein at least a first comparator and a second comparator of the at least one first comparator and at least one second comparator are connected to the inputs of an XOR gate, and each XOR gate connected to the first comparator is connected to precisely one counter.

2. The circuit arrangement as claimed in claim 1 , wherein at least two first comparators with different first energy thresholds are connected to the detector element and there is an XOR gate for each first comparator.

3. The circuit arrangement as claimed in claim 2 , wherein there is a time-delay circuit between a first comparator and the XOR gate thereof.

4. The circuit arrangement as claimed in claim 2 , wherein there is a dead-time circuit between a first comparator and the XOR gate thereof.

5. The circuit arrangement as claimed in claim 2 , wherein at least one output of an XOR gate connected to a first comparator for a lower energy threshold includes a veto circuit, which, when triggered by the output from another first comparator with a higher first energy threshold, blocks the input of the counter of the first comparator with the lower energy threshold.

6. The circuit arrangement as claimed in claim 1 , wherein at least two second comparators with different second energy thresholds are connected to the detector element, wherein the second comparator with the lowest energy threshold and the at least one first comparator are connected to a respective XOR gate, and there is an OR gate for each further second comparator.

7. The circuit arrangement as claimed in claim 1 , wherein the at least one counter is connected to a rate correction circuit in order to correct the measured count rates of the X-ray quanta to an actual flux rate of X-ray quanta.

8. The circuit arrangement as claimed in claim 7 , wherein the rate correction circuit includes a lookup table, which converts the measured count rates of the X-ray quanta to an actual flux rate of X-ray quanta.

9. The circuit arrangement as claimed in claim 7 , wherein the rate correction circuit emulates a polynomial, which converts the measured count rates of the X-ray quanta to an actual flux rate of X-ray quanta.

10. The circuit arrangement as claimed in claim 1 , wherein the circuit arrangement is part of an application-specific integrated circuit on a detector.

11. An application-specific integrated circuit (ASIC) for use in a detector in an emitter-detector system of a CT system with a multiplicity of detector elements, the ASIC including at least one circuit arrangement as claimed in claim 1 for each detector element.

12. The application-specific integrated circuit (ASIC) as claimed in claim 11 , wherein the ASIC is connected to a plurality of detector elements.

13. An emitter-detector system of an X-ray CT system, comprising at least one circuit arrangement as claimed in claim 1 .

14. The circuit arrangement as claimed in claim 3 , wherein there is a dead-time circuit between a first comparator and the XOR gate thereof.

15. The circuit arrangement as claimed in claim 3 , wherein at least one output of an XOR gate connected to a first comparator for a lower energy threshold includes a veto circuit, which, when triggered by the output from another first comparator with a higher first energy threshold, blocks the input of the counter of the first comparator with the lower energy threshold.

16. The circuit arrangement as claimed in claim 4 , wherein at least one output of an XOR gate connected to a first comparator for a lower energy threshold includes a veto circuit, which, when triggered by the output from another first comparator with a higher first energy threshold, blocks the input of the counter of the first comparator with the lower energy threshold.

17. An application-specific integrated circuit (ASIC) for use in a detector in an emitter-detector system of a CT system with a multiplicity of detector elements, the ASIC including at least one circuit arrangement as claimed in claim 2 for each detector element.

18. The application-specific integrated circuit (ASIC) as claimed in claim 17 , wherein the ASIC is connected to a plurality of detector elements.

19. An emitter-detector system of an X-ray CT system, comprising at least one circuit arrangement as claimed in claim 2 .