Time-of-flight Positron emission tomography (TOF-PET) is one of the next-generation medical imaging methods, which requires scintillators with a very short decay time. However, the shortest scintillation decay times are typically 20-30 ns, and these values are not sufficient for TOF-PET. Cherenkov counters are used in high energy physics and they are expected to be applied in medical imaging due to their short decay time. Here, high-refractive index materials are necessary for Cherenkov radiators to reach a high light output. We measured refractive indices of Gd3Ga5O12 (GGG), Y3Ga5O12 (YGG) and Lu3Ga 5O12 (LuGG) crystals grown by a micro-pulling-down (μ-PD) method. The GGG, YGG and LuGG crystals were found to have refractive indices of ~2.5, ~2.3 and ~2.3 at 400 nm, respectively. Then we grew a 40 mm diameter GGG crystal by the Czochralski method, and the emission decay times of the GGG crystals irradiated with muons and gamma rays were 10±1ns and 10±2ns, respectively, using a photomultiplier tube (Hamamatsu R6231-100). Cherenkov light of the GGG crystal could be observed for the gamma-ray irradiation.
|ジャーナル||Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|
|出版ステータス||Published - 2013|
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