  The efficiency of a radiation detector, intended as probability of detection
of an incident quantum, depends on various factors: the detected fraction of
quanta ascribed to the noise-less detector, the intrinsic noise of the
detector, the false events introduced by the detection process and the false
events generated by the detector itself.
  In this paper is treated the role of the false events on the measurement of
the detective quantum efficiency (DQE) of the radiation detectors,
indifferently for counting detectors and imaging detectors.
