Preliminary characterization of a single photon counting detection system for CT application

The aim of this work is to evaluate the capability of a single photon counting acquisition system based on the Medipix2 read-out chip for Computed Tomography (CT) applications in Small Animal Imaging. We used a micro-focus X-ray source with a W anode. The detection system is based on the Medipix2 read-out chip, bump-bonded to a 1 mm thick silicon pixel detector. The read-out chip geometry is a matrix of 256×256 cells, 55 μm×55 μm each. This system in planar radiography shows a good detection efficiency (about 70%) at the anode voltage of 30 kV and a good spatial resolution (MTF=10% @ 16.8 lp/mm). Starting from these planar performances we have characterized the system for the tomography applications with phantoms. We will present the results obtained as a function of magnification with two different background medium compositions. The effect of the reconstruction algorithm on image quality will be also discussed.