X-ray imaging with photon counting hybrid semiconductor pixel detectors

Semiconductor pixel detectors, originally developed for particle physics ex periments, have been studied as X-ray imaging devices. The performance of d evices using the Ohm 3 read-out chip bump-bonded to pixellated silicon semi conductor detectors is characterised in terms of their signal-to-noise rati o when exposed to 60 kVp X-rays. Although parts of the devices achieve valu es of this ratio compatible with the noise being photon statistics limited, this is not found to hold for the whole pixel matrix, resulting in the glo bal signal-to-noise ratio being compromised. First results are presented of X-ray images taken with a gallium arsenide pixel detector bump-bended to a new read-out chip, (MEDIPIX), which is a single photon counting read-out c hip incorporating a 15-bit counter in every pixel. (C) 1999 Elsevier Scienc e B.V. All rights reserved.