Development of a Compton Camera based on digital SiPMs and GAGG crystals

In this work the feasibility of digital silicon Photomultipliers (dSiPM) coupled to GAGG (Gadolinium Aluminium Gallium Garnet) scintillator was tested as a Compton camera system for environmental radiation survey applications. The dSiPM is a newly developed photon counting device by Philips which digitizes the photon counts already on the cell level. One sensor tile consists of 4 × 4 dies with 2 × 2 pixels each. Every pixel contains 3200 cells. Two arrays of 8 × 8 GAGG crystals (crystal size is 3.2 × 3.87 × 8 mm³) are individually coupled to the pixel matrix of two dSiPMs tiles. The scatter detector and the absorbing detector are stacked at 5 cm distance to build the Compton camera system. Data was acquired using a coincidence time window of 3 ns. For the two detectors in coincidence, the measured energy resolution is 9.7 % FWHM@511 keV and coincidence time resolution is ~ 740 ps FWHM. The first image of a 22Na point source located at 25 cm from the Compton Camera was successfully reconstructed using filtered back projection (FBP).