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At the Department of Physics of the University of Pisa, Italy, a new and fully engineered version of the YAP-(S)PET small animal scanner has been recently installed. The new YAP-(S)PET is able to perform both PET and SPECT studies on small animals. The scanner is made up of four heads: each one is composed of a 4 x 4 cm(2) YAlO3:Ce (or YAP:Ce) matrix of 20 x 20 elements, 2 x 2 x 25 mm(3) each, coupled to a Position Sensitive Photomultiplier (PS-PMT) (Hamamatsu R2486). The four modules are positioned on a rotating gantry. The switching to the SPECT modality is easily made by mounting a high resolution parallel hole (0.6 mm circle divide, 0.15 mm septum) lead collimator in front of each crystal. This paper reports the performance of the system in terms of absolute sensitivity and spatial resolution for both PET and SPECT modalities. The scatter fraction and noise-equivalent count rate (NEC) for a mouse phantom for different energy windows have been measured in PET modality. Images of phantoms and animals are also presented

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We have successfully built and characterised a small animal PET based on 4 rotating detectors with a spatial resolution < 2 mm over its field of view and a sensitivity of 640 cps/mu Ci at the centre. The scanner is based on four matrices of 400 YAP:Ce finger crystals (2x2x30 mm(3) each) coupled to Position Sensitive PhotoMultipliers (Hamamatsu R2486-06.) We have now applied two high resolution collimators to two opposite detectors, hence realising an integrated PET-SPECT scanner for small animals. The collimators are made of lead with 20 mm long, 0.6 mm hexagonal holes with 0.15mm septa. The read-out and data acquisition system are handled by NIM-CAMAC standard electronics. The Field Of View (FOV) of the tomograph has a diameter of 4 cm and an axial length of 4 cm in both PET and SPECT configuration which is appropriate for mice and rat studies