Development of a PET detector module with Depth of Interaction capability

The 4DM-PET experiment aims to develop an innovative detector module for PET applications. The device is composed of a continuous LYSO scintillator crystal coupled to two SiPM matrices on its top and bottom surfaces. The peculiarity in using a continuous crystal is the ability to reconstruct the Depth of Interaction of the 511 keV photons generated by the annihilation of the positrons emitted by the radiotracer. A first small prototype module has been built. It is composed of a LYSO crystal, 20×20×10 mm3 coupled on larger surfaces with arrays of SiPMs (4×4 pixel, 4×4 mm2 each). The lateral faces of the crystal slab are black painted to avoid reflection of light. The detector is read by custom designed Front-End ASICs. We have scanned the detector in the three coordinates with pencil beams produced by collimated radioactive sources in order to investigate the module spatial resolution capabilities. The results achieved in terms of Depth of Interaction (DOI) reconstruction and Point Spread Function (PSF) at different positions on the detector surface are presented.