A system and method for evaluating and calibrating a detector (111) in a scanner (110) the system comprises: the detector (111) for receiving radiation in respond to which a plurality of single events occur a photodetector (313) of the detector (111) for generating an electronic signal relating to the plurality of single events a processing module (120) for determining a parameter of the electronic signal relating to the plurality of single events and evaluating the working condition of the photodetector (313) based on the parameter and a threshold.
