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

We propose a new scanner for small animal Positron Emission Tomography (PET) based on stacks of double sided silicon detectors. Each stack is made of 40 planar detectors with dimension 60×60×1mm3 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 are discarded by an exclusive OR applied between each detector plane of a stack. In this way we achieve a precise determination of the interaction point of the two 511keV 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 (11 double sided Si detector layers), divided into two stacks 2cm apart made of, respectively, 5 and 6 prototype layers, placing a small spherical 22Na source in different positions. We report on the results, spatial resolution, imaging and timing performances obtained with double sided silicon detectors, manufactured by ITC-FBK, having an active area of 3×3cm2, thickness of 1mm and a strip pitch of 500μm. Two different strip widths of 300 and 200μm equipped with 64 orthogonal p and n strips on opposite sides were read out with the VATAGP2.5 ASIC, a 128-channel “general purpose” charge sensitive amplifier.