Dose-dependent X-ray measurements using a 64x64 hybrid GaAs pixel detectorwith photon counting

New developments in medical imaging head towards semiconductor detectors fl ip-chip bonded to CMOS readout chips. In this work, detectors fabricated on SI-GaAs bulk material were bonded to Photon Counting Chips.(1) This PCC co nsists of a matrix of 64 x 64 identical square pixels (170 mum x 170 mum) w ith a 15-bit counter in each cell. We investigated the imaging properties o f these detector systems under exposure of a dental X-ray tube. First, a do se calibration of the X-ray tube was performed. Fixed pattern noise in floo d exposure images was determined for a fixed dose and an image correction m ethod, which uses a gain map, was applied. For characterising the imaging p roperties, the signal-to-noise ratio (SNR) was calculated as function of ex posure dose. Finally, the dynamic range of the system was estimated. (C) 20 01 Elsevier Science B.V. All rights reserved.