Detector in an imaging system

1. A method for evaluating a working condition of a photodetector of a detector in an imaging device comprising:

receiving radiation by the detector in response to which a plurality of single events occur;

generating, by the photodetector, an electronic signal relating to the plurality of single events, wherein the electronic signal comprises time related information processed by a time-to-digital convertor (TDC) having multiple TDC channels;

determining a parameter of the electronic signal relating to the plurality of single events; and

evaluating the working condition of the photodetector based on the parameter and a threshold.

2. The method of claim 1 , wherein the electronic signal comprises a pulse signal.

3. The method of claim 1 further comprising:

obtaining a distribution of the plurality of single events with respect to the multiple TDC channels;

selecting a reference channel from the multiple TDC channels;

dividing the multiple TDC channels into a first set of TDC channels and a second set of TDC channels based on the reference channel such that the number of single events of the first set is equal to the number of single events of the second set;

setting a reference time to the reference channel; and

calculating a time value relating to a characteristic TDC channel in the first set according to the reference time.

4. The method of claim 3 , wherein the first set of TDC channels are on one side of the reference channel in a column diagram, and the second set of TDC channels are on the other side of the reference channel in the column diagram.

5. The method of claim 3 , wherein the time value relating to the characteristic TDC channel is calculated based on the reference time, a serial number of the characteristic TDC channel, the single event count of the characteristic TDC channel, and a clock period of the TDC.

6. The method of claim 3 , wherein the reference time is set as half of a clock period of the TDC.

7. The method of claim 1 , wherein the parameter is a single event count or a characteristic of a photon energy spectrum of the radiation.

8. The method of claim 7 further comprising:

assigning the photodetector into a first set if the single event count exceeds the threshold.

9. The method of claim 7 further comprising:

determining the positon of a first peak of the photon energy spectrum;

determining the position of a characteristic peak corresponding to the first peak;

determining a deviation between the position of the first peak and the position of the characteristic peak; and

assigning the photodetector into a first set if the deviation is below the threshold.

10. A system, comprising:

a detector for receiving radiation in respond to which a plurality of single events occur;

a photodetector of the detector for generating an electronic signal relating to the plurality of single events; and

a processing module for determining a parameter of the electronic signal relating to the plurality of single events and evaluating the working condition of the photodetector based on the parameter and a threshold,

wherein the detector comprises a scintillator, and the radiation is generated by the background radiation of the scintillator.

11. The system of claim 10 , the radiation received by the detector is generated by a radiation source placed in a field of view of the detector.

12. The system of claim 10 , wherein the scintillator exhibits at least one characteristic radiation.

13. The system of claim 10 , wherein the scintillator comprises a lutetium compound.

14. The system of claim 10 , wherein the photodetector comprises at least one device selected from a group consisting of a photomultiplier, a silicon photomultiplier, and an avalanche diode.

15. The system of claim 10 , wherein the photodetector is connected with a voltage divider.