First prototype of a gamma-camera based on a single CsI(Tl) scintillator coupled to a silicon drift detector array

A small prototype of gamma-ray detector suitable for both imaging and spectroscopy, based on a single CsI(Tl) scintillator coupled to a two-dimensional Si drift detector (SDD) array, has been developed. The determination of the position of interaction is performed by applying the centroid method to the signals from the single SDD units, while the measurement of the /spl gamma/ photon energy is performed by summing together these signals. This first prototype has been developed in order to evaluate the performances of a CsI(Tl)-SDD detection scheme in view of the realization of larger scintillation cameras for nuclear medicine. The low electronic noise of the SDD allows one to obtain good performance both in position and in energy resolution. A position resolution of the order of 0.6 mm and an energy resolution of about 17% FWHM at 122 keV have been measured.