Introduction
Single-photon emission tomography (SPECT) still suffers from poor quality images. The collimator stops about 99,99% of the gamma rays from reaching the detector. This leads to a small signal to noise ratio. A small increase of this noise induces a larger increase of the noise present in the reconstructed slice. As a consequence it is important to reduce effect of the noise in the acquired data by increasing the system sensitivity. Of course, this has to be done without an increase of the noise instability of the tomography system.