Dose-dependent X-ray measurements using a 64×64 hybrid GaAs pixel detector with photon counting

New developments in medical imaging head towards semiconductor detectors flip-chip bonded to CMOS readout chips. In this work, detectors fabricated on SI-GaAs bulk material were bonded to Photon Counting Chips.11Developed in the framework of the MEDIPIX collaboration: CERN, Universities of Freiburg, Glasgow, Naples and Pisa. PCC consists of a matrix of 64×64 identical square pixels (170 μm×170 μm) with a 15-bit counter in each cell. We investigated the imaging properties of these detector systems under exposure of a dental X-ray tube. First, a dose calibration of the X-ray tube was performed. Fixed pattern noise in flood exposure images was determined for a fixed dose and an image correction method, which uses a gain map, was applied. For characterising the imaging properties, the signal-to-noise ratio (SNR) was calculated as function of exposure dose. Finally, the dynamic range of the system was estimated.