Analog photon counting

1. A photon counting system ( 10 ) comprising:

an analog domain ( 12 );

a digital domain ( 14 ) in communication with the analog domain ( 12 );

a detector ( 20 ) configured to detect photons;

an analog digital converter ( 16 ) in the digital domain ( 14 );

an amplifier circuit in the analog domain ( 12 ) configured to receive the detector's ( 20 ) output, wherein the amplifier circuit's ( 23 ) output is in communication with the analog digital converter ( 16 );

an accumulator ( 24 ) in communication with the analog digital converter ( 16 ), wherein the accumulator ( 24 ) is configured to integrate a signal from the analog digital converter ( 16 ) over a predetermined number of signals and differentiate the integrated signal, wherein a difference between two sample points corresponds to an amount of signal in an associated time bin.

2. The photon counting system ( 10 ) of claim 1 , wherein the detector ( 20 ) comprises an analog detector.

3. The photon counting system ( 10 ) of claim 1 , wherein the detector ( 20 ) comprises at least one of a photo multiplier tube and a hybrid photo-diode.

4. The photon counting system ( 10 ) of claim 3 , wherein the low-pass filter ( 18 ) is configured to provide an integrated pulse profile to the analog digital converter ( 16 ).

5. The photon counting system ( 10 ) of claim 1 , wherein the amplifier circuit comprises a pre-amplifier ( 22 ) and a low-pass filter ( 18 ).

6. The photon counting system ( 10 ) of claim 1 , wherein an accumulator value is stored in a memory ( 26 ).

7. The photon counting system ( 10 ) of claim 6 , wherein the accumulator ( 24 ) is reset to zero after the accumulator value is stored in the memory ( 26 ).

8. The photon counting system ( 10 ) of claim 6 , wherein the accumulator ( 24 ) is configured to integrate the signal from the analog digital converter ( 16 ) over the predetermined number of signals before the accumulator value is reset to zero.

9. The photon counting system ( 10 ) of claim 1 , wherein the predetermined number of signals corresponds to a range bin.

10. The photon counting system ( 10 ) of claim 1 , wherein a filter ( 28 ) is provided between the analog digital converter ( 16 ) and the accumulator ( 24 ).

11. A method for counting photons comprising:

providing a system having an analog domain, a digital domain in communication with the analog domain, and a detector configured to detect photons;

detecting photons with the detector;

integrating a signal of the detector in the analog domain;

digitizing the integrated signal with an analog digital converter in the digital domain;

integrating a signal from the analog digital converter over a predetermined number of signals with and accumulator in communication with the analog digital converter;

differentiating a digital signal of the analog digital converter; and

wherein a difference between two sample points corresponds to an amount of signal in an associated time bin.

12. The method of claim 11 , wherein the signal is sampled at a predetermined resolution.

13. The method of claim 11 , wherein the signal is a current.

14. The method of claim 11 , wherein the detector comprises an analog detector.

15. The method of claim 11 , wherein the detector comprises at least one of a photo multiplier tube and a hybrid photo-diode.

16. The method of claim 11 , wherein the detector signal comprises integrated pulses corresponding to pulse energy.

17. The method of claim 11 , wherein:

detecting photons with the detector comprises capturing a plurality of photons with the detector; and

integrating a signal of the detector in the analog domain comprises integrating a combined energy of the plurality of photons.

18. The method of claim 17 , comprising detecting additional photons with the detector before the signal falls below a predetermined threshold.