DQE as quantum efficiency of imaging detectors
  In this paper a general and unified treatment of the DQE is exposed, both in the space-domain and in the frequency-domain. The meaning of the DQE as quantum efficiency appears to be of paramount importance for a correct interpretation of the physical parameters involved in its formulation and measurement. The treatment in the frequency-domain turns out to be a direct extension of that in the space-domain. An operational procedure is introduced to consider the effect of the filtering of the detector in the space-domain. 
Giovanni Zanella