Characterization of a high-resolution CT scanner prototype for small animals

At the Department of Physics of the University of Pisa and INFN of Pisa, we have assembled a high-resolution CT scanner prototype for small animals. The prototype will be integrated with the YAP-(S)PET scanner, in order to realize a combined PET\\SPECT\\CT scanner for small animals. We have characterized the microCT scanner prototype in terms of spatial resolution and noise using three different X-ray detectors. The first detector (Hamamatsu 57199) is composed by a CsI:Tl layer coupled to a CCD via a 1:1 fiber optic plate; the second detector (Radicon Rad-Eye 4) consists in a flat-panel CMOS sensor, directly coupled to a Ga2O2S:Tb scintillator; the third detector is a 1 mm thick Si detector, bump-bonded to the Medipix2 readout chip. The first two detectors are based on indirect conversion of X-rays and operate in charge integration mode, while the third is a direct conversion detector and operates in photon counting mode. The characterization was carried out using dedicated phantoms for the measurement of spatial resolution and image noise. The results obtained with the three detectors are compared, in order to evaluate the differences in tomographic performances due to the different characteristics of each detector.