High resolution phoswich gamma-ray imager utilizing monolithic MPPC arrays with submillimeter pixelized crystals

T. Kato, J. Kataoka, T. Nakamori, A. Kishimoto, S. Yamamoto, K. Sato, Y. Ishikawa, K. Yamamura, N. Kawabata, H. Ikeda, K. Kamada

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


We report the development of a high spatial resolution tweezers-type coincidence gamma-ray camera for medical imaging. This application consists of large-area monolithic Multi-Pixel Photon Counters (MPPCs) and submillimeter pixelized scintillator matrices. The MPPC array has 4 × 4 channels with a three-side buttable, very compact package. For typical operational gain of 7.5 × 105 at + 20 °C, gain fluctuation over the entire MPPC device is only ± 5.6%, and dark count rates (as measured at the 1 p.e. level) amount to 400 kcps per channel. We selected Ce-doped (Lu,Y) 2(SiO4)O (Ce:LYSO) and a brand-new scintillator, Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) due to their high light yield and density. To improve the spatial resolution, these scintillators were fabricated into 15 × 15 matrices of 0.5 × 0.5 mm2 pixels. The Ce:LYSO and Ce:GAGG scintillator matrices were assembled into phosphor sandwich (phoswich) detectors, and then coupled to the MPPC array along with an acrylic light guide measuring 1 mm thick, and with summing operational amplifiers that compile the signals into four position-encoded analog outputs being used for signal readout. Spatial resolution of 1.1 mm was achieved with the coincidence imaging system using a 22Na point source. These results suggest that the gamma-ray imagers offer excellent potential for applications in high spatial medical imaging.

Original languageEnglish
Article numberP05022
JournalJournal of Instrumentation
Issue number5
Publication statusPublished - 2013 May
Externally publishedYes


  • Gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA)
  • Intra-operative probes
  • Photon detectors for UV, visible and IR photons (solid-state) (PIN diodes, APDs, Si-PMTs, G-APDs, CCDs, EBCCDs, EMCCDs etc)

ASJC Scopus subject areas

  • Mathematical Physics
  • Instrumentation


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