Performance of a medical imaging system for photons in the 60-140 keV energy range

We report the status of the art of a prototype based on a GaAs pixel detect or bump-bonded to a dedicated VLSI chip to be possibly used for imaging in the nuclear medicine field. This device, with a 200 mum thick pixel matrix (64 x 63 square pixels, 170 mum side), has already been tested with very go od results for digital mammography applications (mean energy 20 keV). For m ore energetic photons, as in nuclear medicine, a 600 mum thick detector has been chosen. Using radioactive sources (Am-241, 60 keV and Tc-99m, 140 keV photons) we have measured the performance of our pr otatype in terms of ch arge collection and detection efficiency of the detector, discrimination ca pability of the electronics and imaging properties of the whole system. In particular, we have evaluated the spatial resolution properties measuring t he Point Spread Function and the imaging capabilities using a home made thy roid phantom. We present also the comparison between these results and thos e obtained with a traditional gamma camera and the evaluation, made by both experimental measurements and software simulations, of the geometry relate d to the use of a collimator. (C) 2001 Elsevier Science B.V. All rights res erved.