Measured imaging performance of photon counting hybrid pixel X-ray detectors

The imaging performance of photon counting hybrid pixel X-ray detectors based on the XPAD chip is presented. The noise power spectrum, the modulation transfer function and the detective quantum efficiency of the imaging systems are evaluated in the case of a standard mammography beam and a common micro-CT beam. The study is based on two XPAD3-S chips, connected either to a Si or to a CdTe sensor, the latter being of interest for its higher efficiency. Both detectors consist of 9600 pixels (130 μm × 130 μm) organized in a 80 × 120 matrix and allow for the setting of an energy threshold on the detected photons. Results are given as function of the dose, for typical small animal imaging exposures. The stability and linearity of the detectors and the influence of the energy threshold on the image quality are investigated. Finally, the performance of hybrid pixels is compared with commercially available devices used in mouse computed tomography imaging.