title: Evaluation of a SiPM array coupled to a Gd3Al2Ga3O12:Ce (GAGG:Ce) discrete scintillator.
abstract: OBJECTIVE
  In this study, we present the results of the evaluation of the SensL ArraySL-4 photo-detector, coupled to a 6 × 6 GAGG:Ce scintillator array, with 2 × 2 × 5 mm(3) crystal size elements for possible applications in medical imaging detectors with focus in PET applications. Experimental evaluation was carried out with (22)Na and (137)Cs radioactive sources and the parameters studied were energy resolution and peak to valley ratio.
  
  
  METHODS
  ArraySL-4 is a commercially available, 4 × 4 array detector covering an active area of 13.4 mm(2). The GAGG:Ce scintillator array used in this study has 0.1 mm thickness BaSO4 reflector material between the crystal elements. A symmetric resistive voltage division matrix was applied, which reduces the 16 outputs of the array to 4 position signals. A Field Programmable Gate Array was used for triggering and digital processing of the signal pulses acquired using free running Analog to Digital Converters.
  
  
  RESULTS
  Raw images and horizontal profiles of the 6 × 6 GAGG:Ce scintillator array produced under 511 keV and 662 keV excitation are illustrated. Moreover, the energy spectra obtained with (22)Na and (137)Cs radioactive sources from a single 2 × 2 × 5 mm(3) GAGG:Ce scintillator are shown. The peak to valley ratio and the mean energy resolution values are reported.
  
  
  CONCLUSIONS
  The acquired raw image of the GAGG:Ce crystal array under 511 keV excitation shows a clear visualization of all discrete scintillator elements with a mean peak to valley ratio equal to 40. The mean energy resolution was measured equal to 10.5% and 9% respectively under 511 keV and 662 keV irradiation.
authors.affiliation: Department of Biomedical Engineering, Technological Educational Institute of Athens, Athens, Greece. Electronic address: sdavid@teiath.gr.
authors.forename: S
authors.initials: S
authors.lastname: David
authors.affiliation: Department of Biomedical Engineering, Technological Educational Institute of Athens, Athens, Greece; Department of Medical School, University of Thessaly, Larissa, Greece.
authors.forename: M
authors.initials: M
authors.lastname: Georgiou
authors.affiliation: Department of Biomedical Engineering, Technological Educational Institute of Athens, Athens, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Fysikopoulos
authors.affiliation: Department of Biomedical Engineering, Technological Educational Institute of Athens, Athens, Greece.
authors.forename: G
authors.initials: G
authors.lastname: Loudos
mesh_terms: D055615:Electrical Equipment and Supplies; D049268:Positron-Emission Tomography / Q000295:instrumentation*; D012588:Scintillation Counting / Q000295:instrumentation*
keywords: GAGG:Ce; PET; Silicon photomultipliers (SiPMs)