Discriminator threshold dependency of the zero-frequency DQE of photon-counting pixel detectors

In this paper, we apply the method of calculating the zero-frequency DQE using the concept of an average multiplicity to the Medipix2 detector. This photon counting pixel detector sets a discriminator threshold for the minimum energy needed to trigger a count. The average multiplicity of counts per detected photon and the detection efficiency depend on the threshold setting. Therefore, the DQE depends on this setting. We investigated the impact of physical effects on the DQE and present the according results generated with the Monte Carlo simulation ROSI for monoenergetic and for spectral X-ray sources. An optimum threshold setting can be derived