First measurements for the SiliPET project: A small animal PET scanner based on stacks of silicon detectors

We have proposed a new scanner for small-animal positron emission tomography (PET) based on stacks of double sided silicon detectors. Each stack is composed of 40 planar detectors with dimension 60 times 60 times 1 mm
³
and 128 orthogonal strips on both sides to read the two coordinates of interaction, the third being the detector number in the stack. Multiple interactions in a stack may be discarded. In this way we achieve a precise determination of the interaction point of the two 511 keV photons. The reduced dimensions of the scanner also improve the solid angle coverage resulting in a high sensitivity. Preliminary results were obtained with MEGA prototype tracker. In this work we present the results obtained with double sided silicon detectors, manufactured by ITC-Fondazione Bruno Kessler (Trento- Italy), having an active area of 3 times 3 cm
²
, a strip pitch of 500 mum, strip width of 300 mum and thickness of 1 mm, equipped with 64 orthogonal p and n strips on opposite sides. We are using two different kinds of analog front end electronic chains: a single channel prototype of an ASIC circuit designed by Politecnico di Milano for fast timing measurements and VATAGP2.5 ASIC by IDEAS to evaluate the spatial resolution.