Title :
High position resolution gamma-ray imagers consisting of a monolithic MPPC array with submillimeter pixelized scintillator crystals
Author :
Kato, Toshihiko ; Kataoka, J. ; Nakamori, Toshiki ; Kishimoto, Akihiro ; Yamamoto, Seiichi ; Sato, Kiminori ; Ishikawa, Yozo ; Yamamura, Kazuya ; Nakamura, Shigenari ; Kawabata, Nobuyuki ; Ikeda, Hinata ; Kamada, K.
Author_Institution :
Res. Inst. for Sci. & Eng., Waseda Univ., Shinjuku, Japan
fDate :
Oct. 27 2012-Nov. 3 2012
Abstract :
We report on the development of two versatile, high spatial resolution gamma-ray imagers for medical imaging. One is a compact gamma-ray camera, the other is a tweezers type coincidence imaging system. These applications consisting of a large-area monolithic Multi-Pixel Photon Counter (MPPC) and submilIimeter pixelized scintillator matrices. The MPPC array has 4 × 4 channels with a three-side buttable, very compact package. Each channel has a photosensitive area of 3 × 3 mm2 and 3600 Geiger mode avalanche photodiodes (APD). For a typical operational gain of 7.5 × 105 at + 20 degrees, 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 particularly 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 scintilla tors were fabricated to 22 × 22 or 15 × 15 matrices of 0.5 × 0.5 mm2 pixels. These scintillator matrices were coupled to the MPPC array with an acrylic light guide with 1 mm thick, and signals were read out using the charge division resistor network, which compiles signals into four position-encoded analog outputs. The spatial resolution of 1.2 mm was achieved with the compact gamma-ray camera using collimated 57Co source, and a radiography image of a bearing was successfully obtained. On the other hand, the spatial resolution of 1.1 mm was achieved with the coincidence imaging system using a 22Na source. Furthermore the experimental measurements for a PET scanner was performed, and the spatial resolution of 0.91 mm was achieved. These results suggest that the gamma-ray imagers has excellent potential for their uses as a high spatial medical imag- ng, and also be promising for positron emission tomography (PET).
Keywords :
avalanche photodiodes; biomedical electronics; diagnostic radiography; fluctuations; photon counting; positron emission tomography; resistors; scintillation counters; semiconductor counters; Geiger mode avalanche photodiode; PET scanner; charge division resistor network; cobalt source; fluctuation; gamma-ray camera; high position resolution gamma-ray imager; medical imaging; monolithic MPPC array; monolithic multipixel photon counter array; positron emission tomography; radiography image; size 1 mm; sodium source; spatial resolution; submillimeter pixelized scintillator crystal; tweezer type coincidence imaging system;
Conference_Titel :
Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2012 IEEE
Conference_Location :
Anaheim, CA
Print_ISBN :
978-1-4673-2028-3
DOI :
10.1109/NSSMIC.2012.6551718